Particularities of osteoporosis in thyrotoxic patients ABSTRACT

Transcription

1 THE UNIVERSITY OF MEDICINE AND PHARMACY Gr. T. POPA IAŞI PhD SPECIALTY: ENDOCRINOLOGY Particularities of osteoporosis in thyrotoxic patients ABSTRACT SUPERVISORS: Prof. CARMEN VULPOI, MD, PhD Prof. EUSEBIE ZBRANCA, MD, PhD Doctorand: MONICA ANDREIA HARAS, MD IAŞI 2012

2 Key words: osteoporosis, osteopenia, bone mineral density, thyrotoxicosis, hyperthyroidism, thyrotropin

3 CONTENTS CONTENTS 1 INTRODUCTION 3 ABBREVIATION INDEX 4 CURRENT DATA ON THE SUBJECT MATTER 6 CHAPTER 1. OSTEOPOROSIS Definition, medical importance Classification Pathophysiological considerations Diagnosis Assessment of the bone mineral density Biochemical markers of bone turn-over Management General measures Pharmacological therapy 26 CHAPTER 2. THYROTOXICOSIS Definition and aetiological classification Clinical aspects Clinical presentation Differential diagnosis Paraclinical diagnosis Positive diagnosis Aetiological diagnosis Therapeutic options General measures Antithyroid drugs Radioactive iodine therapy Surgical thyroidectomy Corticosteroids Iodinated contrast agents and lithium compounds Percutaneous interventions Symptomatic management 66 1

4 CHAPTER 3. THYROTOXIC OSTEOPOROSIS 68 Mechanisms of thyrotoxic osteoporosis 68 Bone metabolism in thyrotoxicosis 70 Evolution and prognosis of thyrotoxic osteoporosis 72 PERSONAL RESEARCH 73 CHAPTER 4. STUDY MOTIVATION. HYPOTHESES AND OBJECTIVES 73 CHAPTER 5. PATIENTS AND METHODS Study design Patients 74 The retrospective study 74 The prospective study Assessed parameters Statistical analysis 80 CHAPTER 6. RETROSPECTIVE STUDY ON THE EVOLUTION OF BONE MINERAL DENSITY IN THYROTOXIC PATIENTS, AFTER ATTAINMENT OF EUTHYROIDISM Stratification of the studied groups Results Analysis of the premenopausal groups (C-n and TX-n) Analysis of the postmenopausal groups (C-m and TX-m) Analysis of the postmenopausal groups receiving strontium ranelate (C-s and TX-s) Discussion and conclusions The premenopausal groups (C-n and TX-n) The postmenopausal groups (C-m and TX-m) The postmenopausal groups receiving strontium ranelate (C-s and TX-s) 205 Conclusions 209 CHAPTER 7. PROSPECTIVE STUDY ON THE EVOLUTION OF BONE MINERAL DENSITY IN THYROTOXIC PATIENTS Stratification of the studied groups 211 2

5 7.2. Results 211 Baseline 212 Follow-up Discussion and conclusions 228 Conclusions 233 CHAPTER 8. FINAL CONCLUSIONS 234 References 236 3

6 The thesis comprises 256 pages and it features 8 chapters, 136 tables, 225 figures and 465 reference entries. INTRODUCTION Osteoporosis constitutes the most frequent metabolic disorder of the skeleton; though it used to be regarded as a normal part of the physiological aging proces, at present it is largely acknowledged as a major source of morbidity and mortality, due to the pathological fractures it causes. Because of the increased disability and mortality they involve, as well as high costs of medical care, the prophylaxis of pathological fractures and implicitly the prophylaxis and therapy of osteoporosis have become an important public health issue. From this perspective, it is essential to further develop practical strategies to promptly identify and treat the risk and aetiological factors of osteoporosis. Thyrotoxicosis is currently recognised as a relatively important cause of secondary osteoporosis. This relationship was first suggested by Von Recklinghausen, more than 130 years ago; he described in 1891 a case of severe hyperthyroidism, with multiple fragility fractures. Nowadays, the broad accesibility to modern means of diagnosis and therapy leads to the prompt and efficient treatment of hyperthyroidism, so that the prolonged, severe forms, associated with consistent bone mass loss have become rare. Nevertheless, this association continues to be debated and a considerable number of clinical studies have reported significant reductions of bone mineral density and increases in fracture risk in thyrotoxicosis, even when this state was transient or subclinical. The available data regarding therapy results in hyperthyroid osteoporosis are not yet consistent enough: various rates of bone mass recovery were described, and some authors even described complete normalization after attainment of euthyroidism, even if no specific antiosteoporotic therapy was associated. The present paper aims to assess the severity and reversibility of bone mass loss in thyrotoxic female patients, in relation to the severity of the dysthyroidism. 4

7 CURRENT DATA ON THE SUBJECT MATTER CHAPTER 1. OSTEOPOROSIS Osteoporosis is a chronic, metabolic disorder of the skeleton, which leads to progressive bone loss and microarchitectural deterioration and subsequently, to increased fragility and fracture susceptibility. According to the current reccomandations of the World Health Organization (WHO), its positive diagnosis is based on quantitative assessments of the bone mineral density (BMD). CHAPTER 2. THYROTOXICOSIS The term thyrotoxicosis defines the complex of clinical and paraclinical features consequent to the exposure of the organism to an excessive amount of thyroid hormones, regardless of the cause. The aetiological classification of thyrotoxicosis has the most relevance from the clinical and therapeutic points of view. It should be mentioned that Graves-Basedow disease is considered the most common form of thyrotoxicosis. The distinction between thyroid hyperfunction (hyperthyroidism) and other causes of thyrotoxicosis ( thyroid tissue destruction, exogenous thyrotoxicosis, etc.) has crucial therapeutic implications. The thyroid function often changes during the course of the disease. From a clinical point of view, the most significant disorders are the ones causing a continuous, sustained, overproduction of thyroid hormones. The most frequent forms of thyrotoxicosis fall into this category: Basedow-Graves disease, toxic nodular goiter and toxic adenoma. In thyroiditis (autoimmune, drug-induced, or radiation thyroiditis), the thyrotoxicosis is transitory, with a variable severity and duration, depending on the aetiology, and is frequently followed by hypothyroidism. Understanding the natural history of various aetiological forms of thyrotoxicosis is important for adequate monitoring and 5

8 management. For example, the course of Graves disease is characterized by exacerbation and remission phases; around 10-18% of cases spontaneously progress to hypothyroidism. Graves disease may progress to Hashimoto s thyroiditis with hypothyroidism and conversly, Hashimoto s thyroiditis may evolve to Graves with hyperthyroidims; these changes are most probably in relation to the balance between the inhibiting and stimulating thyroid receptor antibodies (TRAb). Comparison between the main therapeutic directions in hyperthyroidism Antithyroid Radioactive Thyroidectomy drugs iodine Reccurence 60-70% 5-20% 2-10% Compliance Relatively low Good Good Risk of severe adverse effects Hypothyroidism incidence Pregnancy Duration to complete effect 1% 1% Low Low-dose PTU imply no risk Almost inevitable Absolutely contraindicated Low, if performed by an experienced surgeon 30-50% After the middle of the 2 nd trimester 6-8 weeks 2-6 months A few days CHAPTER 3. THYROTOXICOSIC OSTEOPOROSIS Thyrotoxicosis increases bone turnover-ul osos, by reducing the duration of the remodelating cycle, especially the formation phase. This results in an overall decrease of bone mineral density, with a net loss of around 10% of mineralized bone mass per cycle. Mechanisms of thyrotoxic osteoporosis The hyperthyroid bone loss is characterized by increased resorbtion, predominantly in the cortical bone, while the trabecular bone seems to be less affected; this pattern suggests the augmemtation of osteoclast activity as a main mechanism. Some authors suggested that osteoblastic inhibition may also constitute a mechanism of thyrotoxic osteoporosis. While classically, the thyrotoxic bone loss was attributed to high 6

9 circulating levels of thyroid hormones, more recent experimental studies suggested that TSH, which has receptors expressed in osteoblast precursors and osteoclasts, may act as a direct inhibitor of bonne turnover. Therefore, in thyrotoxicosis, the low TSH levels may contribute to the acceleration of bone turnover, with subsequent bone loss. The relative contribution of the thyroid hormones versus thyrotropin in scheletal homeostasis reains a controversial subject. A more recent hypothesis ascribes to TSH a role in the fine regulation of bone metabolism, more evident during the high turnover states, like estrogen deprivation. Some authors also considered the role of IL-6 high levels as a pathophysiological mechanism in thyrotoxic osteoporosis. Since the mononuclear cells express thyroid hormone receptors, the excessive production of IL-6 could be the consequence of their overstimulation by T3. Bone metabolism in thyrotoxicosis The initiation rate of bone remodelling cycles is increased in thyrotoxicosis; while the resorbtion phase seems to maintain its duration and efficiency, the formation phase is shortened and less effective, so that the total length of a cycle is decreased and the end result is an unbalance, favoring bone loss. Studies of calcium and phosphate kinetics in thyrotoxic patients showed an increase in their excretion rate, leading to a negative balance, which in turn probably contributes to the bone demineralization. The markers of bone formation (AP, osteocalcin, P1NP), as well as those of resorbtion (hydroxyproline, pyridinoline and deoxipyridoline, CTX) are raised and their leves seem to correlate with the levels of circulating thyroid hormones. Accelerated collagen degradation, including in soft tissues, amplifies the increases of pyridolines observed in hyperthyroidism. Most studies have described a fall of bone markers levels after initiating the therapy for thyrotoxicosis; this decrease is faster during the first weeks or months and subsequently slows, with the possible exception of bone formation markers, such as AP, wich tend to remain raised. The persistence of formation markers was attributed to the discontinuation of osteoblastic inhibition. Bone turnover normalizes relatively early after initiation of therapy, calcium- 7

10 phosphorus balance becomes positive, and serum as well as urinary, calcium decreases. Some authors described a hypocalcemic phase, sometimes even with tetany, immediately after thyroid status normalization, ascribing it to the temporary increased skeletal retention - the hungry bone syndrome. Evolution and prognosis of thyrotoxic osteoporosis Most studies have shown that effective treatment of the thyrotoxicosis leads to BMD increases, though recovery to normal values has been reported only exceptionally. A significant number of studies have associated hyperthyroidism with incresead fracture risk and even increased mortality, subsequent to femoral fractures. Subclinical hyperthyroidism also seems to have an impact on the skeleton. Most clinical investigations have analysed the mineral density in postmenopausal women. The results showed that in this group, BMD was significantly lowered, regardless of the region of interest, and normalization of thyroid function led BMD improvements. PERSONAL RESEARCH CHAPTER 4. STUDY MOTIVATION. HYPOTHESES AND OBJECTIVES The present work aimed to test the following hypotheses: The BMD decrease correlates with the severity of thyrotoxicosis The BMD decrease correlates with the duration of untreated thyrotoxicosis BMD increase with therapy is faster in thyrotoxic patients than in those with primary osteopenia/ osteoporosis BMD increase with therapy is faster in thyrotoxic patients which attain euthyroidism, than in those who maintain hyperthyroidism despite treatment The major objectives of the study were: The assessment of the relationship between the severity of bone 8

11 loss and thyroid status The assessment of the relationship between the severity of bone loss and hyperthyroidism duration The assessment of the relationship between bone density response to treatment and the evolution of the thyroid function The characterization of the response to therapy of thyrotoxic osteopenia/osteoporosis, in comparison to primary osteopenia/ osteoporosis The estimation of fragility fracture prevalence in thyrotoxic female patients and identification of their risk factors CHAPTER 5. PATIENTS AND METHODS 5.1. Study design We carried out a cohort retrospective study, comparing thyrotoxic female patients, with a baseline BMD below -1 SD, wich attained and maintained euthyroidism with therapy, with euthyroid patients with low bone mass (initial BMD below - 1SD). We also carried out a prospective study, to compare, after initiation of appropriate therapy for hyperthyroidism, the female patients who were euthyroid after 6 months with those who remained thyrotoxic Patients We only included female, caucasian subjects, because currently, there isn t a clear consensus on the accuracy and relevance of the T score calculated using the available data bases, formen under the age of 50. On the other hand, the number of male patients presenting to the Endocrinology Clinic for thyrotoxicosis symptoms, who are assessed and followed for both, thyroid function and bone mineral density, is very low, since the prevalence and incidence of thyrotoxicosis are much lower in men, compared to women. The retrospective study The study group (TX) comprised 153 patients with newly diagnosed thyrotoxicosis and osteopenia/ osteoporosis, with attained and maintained euthyroidism at the subsequent reassessements It 9

12 shoul be mentioned that each case underwent multiple reassessments for thyroid status and treatment adjustments, but we only considered two follow-ups, that included BMD measurements. Inslusion criteria: TSH < 0.27 mu/l at baseline T score, measured at the lumbar spine, -1 SD at baseline TSH in reference range ( mui/l) at both follow-ups Inclusion criteria: Personal history of thyroid disease Other endocrine disorders associated with abnormal bone metabolism Skeletal disorders (bone dysplasias, rheumatismal diseases, primary and secondary bone neoplasms) Personal history of disordes and treatments with a significant impact on bone metabolism Severe diformities of lumbar spine, altering the results of BMD measurements BMD; vertebral fractures, identified radiologically; a difference > 1DS between the T scores of two adjacent vertebrae, even in the absence of a previouos fracture diagnosis; the presence of cement or metallic osteosynthesis material in lumbar spine Lack of compliance to therapy, noted by a doctor in the patient s record All patients were efficiently treated for thyrotoxicosis (with antithyroid drugs, percutaneous injection, or thyroidectomy, depending on the aetiology and the patient s option). All patients received calcium (1000 mg/day) and vitamin D (800 IU/day), and the cases presenting with hypomagnesemia also received Mg supplements. In cases with a T score belor -3 DS, or with a history of fragility fractures, bisphophonates (alendronate, 35 mg/week) or strontium ranelate (2 g/day) were administered. The control group (C) comprised 189 euthyroid patients, with newly diagnosed osteopenia/osteoporosis, in whom thyroid status was also assessed at two subsequent visits. Inclusion criteria: T score, measured at the lumbar spine, -1 SD at baseline TSH in reference range ( mu/l) at all visits 10

13 ft4 in reference range (12-22 ng/dl) la all visits Exclusion criteria were the same with those applied for group TX, plus thyroid disorders of any type, at presentation. All patients received calcium and vitamin D, and the ones with hypomagnesemia also received magnesium. In cases with a T score less -2.5 DS, or a history of fragility fractures, bisphophonates (alendronate, 35 mg/week) or strontium ranelate (2 g/day) were administered. The prospective study We examined the BMD changes (regardless of its values at baseline) in female patients with newly diagnosed thyrotoxicosis, from January to March 2011, after 6months of treatment. The study subgroups were defined at the 6 months follow-up: we compared the patients in whom euthyroidism was obtained and maintained (A), with those who remained hyperthyroid under treatment (B). Initially, 72 patients were enrolled, but 9 of them did not show up for the 6 months reassessment, and 12 were hypothyroid at folloe-up. Finally, we analysed 52 de cases. Subgroup A (33 subiects) had as inclusion criteria: TSH < 0.27 mu/l at baseline TSH in reference range ( mui/l) after 6 months The exclusion criteria were the same with the ones used in the retrospective study. Subgroup B (21 subiects) had as sole including criterion TSH < 0.27 mu/l at both, baseline and 6 months follow-up. The exclusion criteria were the same as in the retrospective study, plus conditions that could have altered the accuracy of whole body BMD assessments: Osteosynthesis materials at any skeletal site Recent fractures at any skeletal site Severe osteoarthrosis, with large, numerous osteophytes 5.3. Assessed parameters 1. Age at presentation, in years 11

14 2. Provenance community (urban U or rural R) 3. History of fragility fractures (to minimumal impact, eg. samelevel falls) 4. Body mass index (BMI, in kg/m 2 ) It was calculated using the formula: where G is body weight, expressed in kilograms and T is height, expressed in metres. 5. Menopause onset in years (if the case) 6. Years since menopause (the difference, in years, between the age at presentation and the age at menopause onset) The study groups were each stratified according to the menopausal status. 7. Smoking (more then 10 cigarrettes a day, for more then 6 months) 8. Alchool consumption (defined as consumption of more then 500 ml/day of bere, 250 ml/day of wine, or 50 ml vodka/brandy) 9. Duration of hyperthyroidism symptoms, in months (if the case). This is a subjective parameter with orientative value. We recorded the time (estimated by the patient) elapsed since the the onset of the most significant symptoms (weight loss with hyperfagia, thermophobia, anxiety, agitation, sleep disturbances, tremor, palpitations),untill the presentation. 10. TSH (thyrotropin) An immonochemical method was used, with electrochemiluminescence immunoassay ECLIA. Measurements were done with an Elecsys System 2010 dispositive (Roche Diagnostics GmbH, Mannheim, Germania). The reference range for adults are miu/l. The detection limit of this test is miu/l. 11. ft4 (free thyroxine) It was determined by ECLIA, using Elecsys System 2010 (Roche Diagnostics GmbH, Mannheim, Germania). The reference range for adults are pmol/l, detection limit is 0.3 pmol/l. 12.Bone mineral density was expressed as absolute density (BMD, in g/cm 2 ) and as T score (Ts). 12

15 It was assessed using a DXA Hologic dispositive, model Delphi W (S/N 70490), the same for all patients. Measurements were made by the same person, for all visits. 13. Serum total calcium (Ca) It was assessed by spectrophotometry, using an Abbot Aeroset analyzer. Reference range for adults is mg/dl ( mmol/l, conversion factor 0.25), detection limit is 0.2 mg/dl (0.05 mmol/l). 14. Calculated ionized serum calcium (Ca ++ ) We used the Zeisler formula: where: Ca ++ ionized serum calcium (mg/dl), Ca total calcium (mg/dl), PT total plasma protein (g/dl). The reference range for adults is mg/dl. This method is less accurate then direct measurement, because the actual value valoarea reală of free calcium significantly depends on the binding fraction. 16. Serum phosphorus (P) It was assessed by spectrophotometry, using an Abbot Aeroset analyzer. Reference range for adults is mg/dl ( mmol/l, conversion factor 0.323), detection limit is 0.3 mg/dl (0.1 mmol/l) for this test. 17. Serum magnesium (Mg) It was measured by spectrophotometry, using an Abbot Aeroset analyzer. Reference range for adults is mg/dl ( meq/l, conversion factor 1.215), detection limit is mg/dl (0.125 meq/l). 18. Total alkaline phosphatase (AP) It was measured by spectrophotometry, using an Abbot Aeroset analyzer. Reference range for adults is U/l. 19. Calciuria It was assessed by spectrophotometry, using an Abbot Aeroset analyzer. Reference range for adults is mg/24 hours. 20. Osteocalcin It was determined by ECLIA. The reference ranges for women 13

16 are: premenopause: ng/dl postmenopause: ng/dl the detection limit is 0.5 ng/ml OH vitamin D It was measured by High Performance Liquid Chromatography HPLC, utilising a Roche analyzer. Reference range for adults is: ng/ml. From a clinical point of view, serum values of 25-OH vitamin D can reflect: Deficiency: <10 ng/dl Insuficiency: ng/dl Suficiency: ng/dl Toxicity: >100 ng/dl 5.4. Statistical analysis Statistical analysis was done under the guidance of Assis. Prof. Cristina Dascălu, UMF Gr. T. Popa. We used SPSS (Statistical Package for the Social Sciences) 16.0, for Windows. The normality of distribution for the obtained data was analyzed using the Kolmogorov-Smirnov test (if p>0.05, then the distribution of the values was considered normal). To assess the differences between parametric data, we used the t-test, if the values were normally distributed; otherwise, the Mann-Whitney test was applied. To determine whether the differences observed at succesive asseessments of a parameter, in the same gruop, had statistical significance, we applied the paired samples t-test. In order to determine if the differences observed between the study and control groups were significant, we used the independent samples t-test. We assessed the linear relanship between parameter pairs through the Pearson bivariate corelation coeffcient (r) and we developed multiple linear regression models. The correlation between two parameters was considered significant if r 2 > We used the chi-square test to compare non-parametric data. The univariate dispersional analysis (comparison between samples grouped a discrete variable) was done using the one-way ANOVA 14

17 test (ANalysis Of VAriance). The obtained values were considered statistically significant if p < CHAPTER 6. RETROSPECTIVE STUDY ON THE EVOLUTION OF BONE MINERAL DENSITY IN THYROTOXIC PATIENTS, AFTER ATTAINMENT OF EUTHYROIDISM 6.1. Stratification of the studied groups Stratification of the groups in the retrospective study Control (C) Thyrotoxicosis (TX) Total Non-menopause (n) Postmenopause Did not receive strontium (m) Strontium treatment (s) The control group (C) was divided in 3 subgroups: Premenopause (C-n) 20 patients (10.58%), treated with vitamin D and calcium Postmenopause (C-m) 153 patients (80.95%), treated with vitamin D, calcium +/- bisphosphonates Postmenopausal patients, treated with vitamin D, calcium and strontium ranelate (C-s) 16 (8.47%) The study group (TX) was divided as follows: Premenopause (TX-n) 22 patients (14.38%), treated with vitamin D and calcium Postmenopause (TX-m) 118 pateients (77.12%), treated with vitamin D, calcium +/- bisphosphonates Postmenopausal patients, treated with vitamin D, calcium and strontium ranelate (TX-s) 13 (8.5%) 15

18 6.2. Results Analysis of the premenopausal groups (C-n and TX-n) Baseline age, intervals between assessments and bone mineral density changes for the premenopausal groups C-n TX-n Baseline age (years) Duration of thyrotoxicosis symptoms (months) Interval 1 (months) Interval 2 (months) Total follow-up (months) ± ± ± ± ± ± ± ± ± Total BMD increase (g/cm 2 ) 0.048± ±0.030 Total Ts increase (SD) 0.38± ±0.21 Group C-n: the values medii (±DS) ale parametrilor studiaţi, pe etape Parameter Baseline (1) Follow-up (2) Follow-up (3) TSH (miu/l) ft4 (pmol/l) BMD (g/cm 2 ) Ts (SD) 1.85± ± ± ± ± ± ± ± ±1, ± ± ± BMI (kg/m 2 ) 25.06± ± ±3.39

19 Parameter Baseline (1) Follow-up (2) Follow-up (3) Ca (mg/dl) Ca ++ (mg/dl) P (mg/dl) Mg (mg/dl) AP (U/l) ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± Group TX-n: mean values (±SD) of the studied parameters Parameter Baseline (1) Follow-up (2) Follow-up (3) TSH (miu/l) ft4 (pmol/l) BMD (g/cm 2 ) Ts (SD) BMI (kg/m 2 ) Ca (mg/dl) Ca ++ (mg/dl) 1.85± ± ± ± ± ± ± ± ± ± ± ± ± ± ±1, ± ± ± ± ± ±

20 Parameter Baseline (1) Follow-up (2) Follow-up (3) P (mg/dl) Mg (mg/dl) AP (U/l) 3.40± ± ± ± ± ± ± ± ± Comparing the mean increases of the bone mass achieved in the two groups, we found that the gain was significantly higher for group TX-n, the changes of BMD and Ts being significantly more important at both, the first reassessment (p=0.011, respectiv p=0.039), and the second (p=0.014, respectiv p=0.007). Comparison between the total BMD increases in the two groups of premenopausal patients Analysis of the postmenopausal groups (C-m and TX-m) For these groups, we introduced the parameter years since menopause, to assess the correlations between bone mineral density and the duration of estrogen deprivation. 18

21 Baseline age, intervals between assessments and bone mineral density changes for the postmenopausal groups C-m TX-m Baseline age (years) Menopause onset (years) Years since menopause (years) Duration of thyrotoxicosis symptoms (months) Interval 1 (months) Interval 2 (months) Total follow-up period (months) ± ± ± ± ± ± ± ± ± ± ± ± ± Total BMD increase(g/cm 2 ) 0.039± ±0.029 Total Ts increase (SD) 0.37± ±0.22 Group C-m: mean values (±SD) of the studied parameters Parameter Baseline (1) Follow-up (2) Follow-up (3) TSH (miu/l) ft4 (pmol/l) BMD (g/cm 2 ) 1.85± ± ± ± ± ± ±1, ± ±

22 Parameter Baseline (1) Follow-up (2) Follow-up (3) Ts (SD) BMI (kg/m 2 ) Ca (mg/dl) Ca ++ (mg/dl) P (mg/dl) Mg (mg/dl) AP (U/l) -1.91± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± In the control group, 29 patients (18.83%) a history of nonvertebral pathological fractures. Group C-m: prevalence of non-vertebral fragility fractures Pacients with antecedents of non-vertebral fractures were significantly older than the ones without (p=0.000); they also had significant lower bone density indices (p=0.000 for both, BMD and Ts) and a lower BMI mean value (p=0.000). The other other studied 20

23 parameters were not significantly different in the fracture group. Although the mean values of TSH were lower in patients with fractures, and the mean values of ft4were higher, the ANOVA test did not find statistically significant differences between the two subgroups (p=0.062 for TSH, p=0.067 for ft4). To further explore the relationship between previuos fragility fractures fractures and the thyroid function, we stratified the values of TSH and ft4 in quartiles and compared the prevalence of nonvertebral pathological fractures within these quartiles (chi-square test). Group C-m: prevalence of non-vertebral fractures by TSH quartiles TSH quartiles Fracture history No fractures 1 ( mui/l) 13 (29.55%) 31 (70.45%) 2 ( mui/l) 8 (24.24%) 25 (75.76%) 3 ( mui/l) 5 (13.16%) 33 (86.84%) 4 ( mui/l) 3 (7.89%) 35 (92.11%) Group C-m: prevalence of non-vertebral fractures by TSH quartiles The chi-square test showed a significantly higher prevalence of fragility fractures in the lowest TSH quartile (29.55%), in comparison to the highest quartile (7.89%, p=0.034). The fracture prevalence was similar in the other TSH quartiles. Group C-m: prevalence of non-vertebral fractures by ft4 quartiles ft4 quartiles Fracture history No fractures 1 ( pmol/l) 3 (7.69%) 36 (92.31%) 21

24 ft4 quartiles Fracture history No fractures 2 ( pmol/l) 8 (21.05%) 30 (78.95%) 3 ( pmol/l) 6 (15.38%) 33 (84.62%) 4 ( pmol/l) 12 (32.43%) 25 (67.57%) Group C-m: prevalence of non-vertebral fractures by ft4 quartiles Statistical anlaysis demonstrated a significanly higher prevalence of non-vertebral fragility fractures in the superior ft4 quartile (32.43%), in comparison to the lowest one (7.69%, p=0.007). The fracture prevalence was similar in the other ft4 quartiles. Group TX-m: the mean values (±SD) of the studied parameters Parameter Baseline (1) Follow-up (2) Follow-up (3) TSH (miu/l) ft4 (pmol/l) BMD (g/cm 2 ) Ts (SD) BMI (kg/m 2 ) 0.12± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

25 Parameter Baseline (1) Follow-up (2) Follow-up (3) Ca (mg/dl) Ca ++ (mg/dl) P (mg/dl) Mg (mg/dl) AP (U/l) 9.83± ± ± ± ± ± ± ± ± ± ± ± ± ± ± In the study group, 29 patients (24.58%) had a history of nonvertebral pathological fractures. Group TX-m: prevalence of non-vertebral fragility fractures The mean TSH values were significantly lower in patients with non-vertebral fractures ( p=0.026), the ft4 values were higher but ANOVA test revealed no statistically significant differences between the two groups (p=0.246). We stratified the ft4 and TSH values in quartiles and we compared the prevalence of pathological fractures. Analysis showed a significantly lower prevalence of non-vertebral fragility fractures in top quartile of TSH (0%) than the other three quartiles (p = 0.006). Differences between the other TSH quartiles were not significant (p> 0.05). 23

26 Group TX-m: prevalence of non-vertebral fractures by TSH quartiles TSH quartiles Fracture history No fractures 1 ( mui/l) 10 (31.25%) 22 (68.75%) 2 ( mui/l) 8 (27.59%) 21 (72.41%) 3 ( mui/l) 11 (32.35%) 23 (67.65%) 4 ( mui/l) 0 (0%) 23 (100%) Group TX-m: prevalence of non-vertebral fractures by TSH quartiles Group TX-m: prevalence of non-vertebral fractures by ft4 quartiles ft4 quartiles Fracture history No fractures 1 ( pmol/l) 5 (17.86%) 36 (82.14%) 2 ( pmol/l) 8 (26.67%) 30 (73.33%) 3 ( pmol/l) 7 (23.33%) 33 (76.67%) 4 ( pmol/l) 9 (30.00%) 25 (70.00%) Group TX-m: prevalence of non-vertebral fractures by ft4 quartiles 24

27 Although the prevalence of fractures in the upper quartile of ft4 (30%) wass higher than in the lower quartile (17.86%), statistical analysis showed no significant difference (p=0.220). The bone density increase was significantly higher for group TXm, Ts and BMD variations showing significant differences both at the first reassessment (p = and p = 0.059), and between the first and third assessment (p=0.026, respectively p=0.048). Comparison between total BMD increases in the two groups of menopausal patients The evolution of the mean Ts values in groups C-m and TX-m, at the 3 successive assessments 25

28 Analysis of the postmenopausal groups receiving strontium ranelate (C-s, TX-s) Baseline age, intervals between assessments and bone mineral density changes, for the postmenopausal groups receiving strontium ranelate C-s TX-s Baseline age (years) Menopause onset (years) Years since menopause (years) Duration of symptoms (months) Interval 1 (months) Interval 2 (months) Total follow-up period (months) Total BMD increase (g/cm 2 ) Total Ts increase (SD) ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± Group C-s: the mean values (±SD) of the studied parameters Parameter Baseline (1) Follow-up (2) Follow-up (3) TSH (miu/l) 1.772± ± ±

29 Parameter Baseline (1) Follow-up (2) Follow-up (3) ft4 (pmol/l) BMD (g/cm 2 ) Ts (SD) BMI (kg/m 2 ) Ca (mg/dl) Ca ++ (mg/dl) P (mg/dl) Mg (mg/dl) AP (U/l) 17.05± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± Group TX-s: the mean values (±SD) of the studied parameters Parameter Baseline (1) Follow-up (2) Follow-up (3) TSH (miu/l) ft4 (pmol/l) BMD (g/cm 2 ) 0.080± ± ± ± ± ± ± ± ± Ts (SD) -3.30± ± ±0.53

30 Parameter Baseline (1) Follow-up (2) Follow-up (3) BMI (kg/m 2 ) Ca (mg/dl) Ca ++ (mg/dl) P (mg/dl) Mg (mg/dl) AP (U/l) ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± The bone mass gain was significantly higher for group TX-s. The mean BMD and Ts were significantly higher both at the first reassessment (p=0.000), and at the second (p= for BMD, p=0.014 for the Ts changes). Total increases of BMD and Ts, over the entire monitoring period, were significantly higher in group TX-s as compared to C-s (p=0.005 for BMD and p=0.002 for Ts changes). The evolution of the mean BMD values in groups C-s and TX-s, at the 3 successive assessments 28

31 6.3. Discussion and conclusions Premenopausal groups (C-n and TX-n) In this group there were no pathological fractures beforepresentation, or during the study. The mean age at baseline was similar in the two groups (46.10 years in group C-n, respectively years in Tx-n). The average values of body mass index were significantly lower in group TX-n at the first two evaluations, but at the third assessment we no longer found significant differences from control. The BMI increase is consistent with the remission of hypercatabolic status associated with thyrotoxicosis. Total serum calcium, free calcium, serum phosphorus and alkaline phosphatase had significantly higher mean values at baseline in group TX-n, but until the first follow-up (after about 1 year) decreased significantly, so that they were similar, at both reassessments, with those observed in group C-m. These differences observed at baseline, as well as the evolution in time of these parameters, are consistent with data from other studies that have associated thyrotoxicosis with elevated serum levels of calcium, phosphorus and AP, and reported improvements after a few months to one year after initiating specific therapy. Serum magnesium had significantly lower average values in the study group at presentation. Subsequently, the values increased significantly and became similar with those found in the control group. The mean values of BMD and Ts measured at the lumbar spine were discretely (not statistically significant) lower in group TX -n, and remained so throughout our study, although significantly increased at both the first and the second reassessments. In group C- n, significant increases of BMD and Ts were also observed at the first and second follow-up. In the C-n group, the initial mean values of bone density indices were strongly and positively correlated with BMI, and negatively, weakly, with age. Also, there was a weak, negative, correlation, between the baseline T-score and alkaline phosphatase levels, which had average values in the range of reference in this group; for BMD, 29

32 this correlation was not significant. The inverse relationship between AP and total bone mineral density is due to increased bone isoenzyme (BAP), reflecting the increased bone turnover, associated with bone loss. BAP is responsible for approximately 50% of the total activity of PA, so in the absence of liver disease ( causing increases of the liver isoform), total AP reflects the overall rate of bone turnover with acceptable accuracy, as confirmed by previous studies. Multiple linear regression revealed age, BMI and serum calcium as the most important determinants of BMD and Ts at baseline. Serum calcium was in inverse relationship with bone density. This negative relationship could be explained, on the one hand, by increased release of calcium from the skeleton, associated with high bone turnover states, and on the other, by the profile of phosphocalcic metabolism in patients with vitamin D deficiencies, who develop a secondary hyperparathyroidism, with mobilization of calcium from bone. BMD and Ts increases observed during follow-up in the control group were positively correlated, at first, as well as at the second follow-up, with duration of therapy. Therefore a direct correlation was observed between the total duration of treatment and the total increases of bone density indices. The multiple regression models constructed identified the duration of treatment as the single predictor for BMD changes, with the exception of the BMD variation at the first reassessment, that was also negatively correlated with calcium changes and impacts. So the increase bone mineral density was associated, at the first follow-up, with decreases of serum calcium levels. Normalization of bone metabolism, with progressively increased retention of calcium from the skeleton could be an explanation for this finding. In the TX-n group, baseline bone density indices were negatively correlated with age, duration of hyperthyroidism symptoms and with ft4 levels. We also found a strong, positive, correlation with BMI and a moderate direct correlation with TSH. In the study group, multiple linear regression revealed BMI and TSH as the strongest positive predictors of BMD and Ts at baseline. Other contributors to the regression models were: age at baseline, 30

33 AP, ft4 and ionized calcium, as negative predictors. Belsing et al., 2010, described ft4as the strongest negative predictor of BMD in a group of premenopausal women with Graves' disease. At the first follow-up, increases of bone density indices were correlated strongly, positively, with the duration of therapy and with TSH raises. Also, they strongly correlated with the AP decreases. In multiple regression models, the AP changes were the strongest determinants of BMD and Ts increases, with a negative (inverse) impact on the model. Inverse correlation between changes in bone density and alkaline phosphatase after normalization of thyroid status confirms previous studies. At the second follow-up, the increases bone density indices correlated only with the therapy duration, which was the only determinant (with positive impact) in the regression models. The BMD increase in group C-n was 3.25% in the first year (until the first follow-up) and of 2.53% in the second, a total of 5.78% over the first examination (ie. after an average time of 23 months). The BMD increase in group TX-n was 5.22% during the first observation period and 3.36% during the second, with a total of 8.58% over the first evaluation; this gain was significantly higher than that obtained in the control group. Also, the T score increase in the study group (0.53 SD) was significantly higher than that observed in group C-n (SD 0.38, p = 0.007) in the 23 months of therapy. In conclusion, in our study, premenopausal hyperthyroid patients showed a faster bone mass gain, in comparinson to patients with osteoporosis / osteopenia and this was especially obvious during the first year after initiation of therapy. So far, there have been few studies on the evolution of bone density in young tireotoxic, premenopausal patients, after normalization of thyroid function. A 1997 study on 17 patients (14 women before menopause and 3 men, with ages between 27 and 48 years) has reported an increase in mean BMD at the lumbar spine of approximately 5.71% and 6.72% at the hip. Another study analyzed by comparison the evolution of a group of 45 hyperthyroid patients, stratified by sex, menopausal status and type of therapy received (antithyroid drugs or antithyroid drugs plus 31

34 salmon calcitonin) at 0, 9 and 18 months of treatment. The authors reported significant increase in bone density in all groups, including non-menopausal women, but this gain was limited to the first 9 months of treatment. Furthermore, this study has revealed no difference in bone mass or bone turnover markers changes between women and men, women before menopause or after, or depending on the association of antiresorptive therapy. Belsinget al., 2010, have analyzed the evolution of 32 premenopausal women diagnosed with Graves-Basedow disease, after 18 months of treatment with antithyroid drugs and found a mean T score increase at lumbar level of 0.8 SD The postmenopausal groups (C-m and TX-m) Menopause may exacerbate the bone loss in thyrotoxicosis, through the synergistic effects on bone, of the hypogonadism with increased levels of thyroid hormones. In our study group, mean age at baseline was similar in the two groups (61.75 years for group C-m, respectively years for T-x). Age at menopause onset was significantly higher in the study group. There were no significant differences between TX-m and C-m in terms of environment of origin, smoking, or alcohol consumption. The prevalence of fragility fractures was slightly (not significantly) lower in control group. The interval until the first follow-up was similar (approximately 11 months) for the two groups, as well as the interval to the second follow-up (about 12 months). All the patients received calcium and vitamin D. 75 (49.02%) patients in group C -m and 39 (33.05%) in TX-m also received alendronate The mean values of body mass index were significantly lower in group TX-m at the first two assessments and, although increased during follow-up, they remained significantly lower than those observed in control group. Total serum calcium, ionized calcium, phosphorus and alkaline phosphatase had significantly higher mean values at baseline in group TX-m. These differences observed at baseline are consistent with data from other studies that have associated thyrotoxicosis with elevated serum levels of calcium, phosphorus and AP. Subsequently, the average values of total serum calcium decreased 32

35 and became comparable with those obtained in group Cm. The ionic calcium values decreased significantly and, although at the first reassessment they were still significantly higher than the control group, at the second follow-up, free calcium values were significantly lower those found in the C-m group. These differences could be explained by poor adherence of the patients to the treatment with calcium and vitamin D preparations. The mean values of serum phosphorus decreased significantly in group TX-m, so that they were statistically similar with those found in the control group, at the first and the second follow-up. AP declined steadily and significantly at both reassessments, but was still significantly higher in the study group than in C-m at the first follow-up; at the second follow-up, AP was comparable in the two groups. This evolution is consistent with data from other studies, describing an increase in alkaline phosphatase in the first 3 months of treatment, followed by a slow decrease, over several months (sometimes more than 12 months), the persistence of increased values reflecting a high rate of osteoformation. Mean values of serum Mg were significantly lower in the study group at baseline. Subsequently, the magnesium mean values increased significantly and became similar with those found in the control group. The mean values of BMD and Ts at the lumbar spine were discretely (not significantly) lower at baseline in group TX -m, but increased significantly, so that they were statistically higher than those in group C-m, at the first reassessment, as well as at the second. In the control group, significant increases were observed in BMD and Ts at the first follow-up, as well as at the second (p=0.000), although the observed values remained below those found in the TX-m group. Comparing the values of the studied parameters in patients with a history of pathological fractures, in the group C-m, with those observed in the patients without fractures, we found that history of fractures was significantly associated in the control group, with older age, longer duration of postmenopause, and lower mean values of BMD and Ts, as well and a lower body mass index (p=0.000 for all specified parameters). So we did not detecte significant differences in 33

36 TSH and ft4 mean values between the euthyroid subgroups with and without a history of fractures. But strtifying the TSH values in group C-m, we found a significantly higher prevalence of pathological fractures in the lowest quartile of TSH, in comparison to the highest, suggesting that the high-normal TSH values could exert a protective effect against the risk of fractures, while the values of within lower limit of normal may predispose to fragility fractures. These results are, for the most part, consistent with data from other studies: Mazziotti et al., 2010, in a retrospective study of 130 postmenopausal women, reported a high prevalence of pathological fractures in euthyroid patients with TSH in the lower tertile. Also, in euthyroid patients, our statistical analysis revealed a significantly higher prevalence of pathological fractures in the upper quartile of ft4, in comparison to the lowest quartile. These results are also consistent with some data reported by other authors: in the OPUS study (The Osteoporosis and Ultrasound Study), 2010, including 2374 postmenopausal euthyroid patients, the authors described an increased risk of non-vertebral fractures in patients with high-normal circulating levels of ft4 or ft3. In the TX-m group, the subgroup of patients with a history of pathological fractures had the same characteristics with those described in the control group and in addition, had a longer duration of thyrotoxicosis symptoms (as compared to the hyperthyroid patients without fractures), significantly lower TSH values, and significantly higher mean values of total serum calcium and phosphorus. No statistically significant differences were found in ft4 values, according to history of fractures. We compared, within the TX-m group, the subgroup with subclinical thyrotoxicosis, with the subgroup with overt thyrotoxicosis. Subclinical hyperthyroidism was associated with significantly higher values of TSH, the BMD, Ts, BMI and the serum Mg at baseline, and with significantcantly lower values of Ca, P and AP. The prevalence of pathological fractures was statistically similar in the two subgroups. In patients with subclinical thyrotoxicosis, history of fractures did not associate with significant differences in TSH, ft4, or the duration of symptoms, while in the subgroup with 34

37 overt thyrotoxicosis, the patients with fragility fractures had lower TSH values and longer durations of symptoms before presentation compared to those without history of fracture. At folloe-up, the only significant differences between patients with subclinical thyrotoxicosis and those with overt hyperthyroidism were higher mean BMD, Ts and BMI values, found in the group with subclinical thyrotoxicosis. In group C-m, the initial values of bone density indices showed a weak, positive, correlation with BMI and a negative one with age and years elapsed since menopause. This negative correlation between bone density and duration of estrogen deprivation is already a known fact, and many studies have described very similar results with ours, with the years of menopause being a stronger predictor for bone mass than age. Multiple linear regression revealed BMI and years since menopause as the only significant determinants of baseline BMD and Ts, in group C-m. The BMD and Ts increases observed at the first follow-up in the control group showed the most significant correlation with the duration of therapy. They also were negatively correlated with AP changes and positively, with the variation in BMI. We also detected weak negative correlations between increased BMD on the one hand, and variations of total and ionized calcium on the other hand, and between T score changes and serum phosphorus changes. At the second follow-up, the only significant correlation was the positive one, between the duration of therapy and the increase of BMD, respectively Ts. Multiple regression models have showed that the strongest predictor for changes in bone density at the first follow-up was the duration of therapy; other factors with significant impact on the models were: BMI changes (positively correlated with BMD and Ts), calcium and phosphatase alkaline variations (negative correlations). At the second follow-up, duration of treatment was still the strongest predictor, to the variations of bone density also contributed the BMI (positive correlation) and calcium (negative correlation) changes. In the TX-m group, baseline bone density indices were negatively, moderately, correlated with the ft4 values and with the symptoms 35