Vitamin D, parathyroid hormone and metabolic syndrome the PORMETS study

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1 Rposo et l. BMC Endocrine Disorders (2017) 17:71 DOI /s RESEARCH ARTICLE Vitmin D, prthyroid hormone nd metbolic syndrome the PORMETS study Open Access Luís Rposo 1,2*, Sndr Mrtins 2,3, Dniel Ferreir 2, João Tigo Guimrães 2,3,4 nd An Cristin Sntos 1,2,5 Abstrct Bckground: Vitmin D (VitD) nd prthyroid hormone (PTH) ply importnt roles in clcium metbolism nd skeletl homeostsis. Estimtes of the VitD sttus in severl Europen countries show lrge vritions between them. In ddition, no ntionl popultion-bsed estimte hs been published. VitD nd PTH my lso ply importnt roles in crdiovsculr risk, which hs been suggested to be ssocited with metbolic syndrome (MetS) nd is very prevlent in Portugl. The gol of our study ws to evlute the prevlence of hypovitminosis D nd its determinnts s well s PTH serum level determinnts nd ssocitions of the 25-hydroxyvitmin D nd PTH serum levels with MetS nd its individul components in smple of the Portuguese minlnd popultion. Methods: PORMETS is ntionl cross-sectionl study tht includes totl smple of 4095 dults. A subsmple, including 500 prticipnts, ws rndomly selected for the present study. A structured questionnire ws dministered to collect informtion on personl medicl histories nd socio-demogrphic nd behviorl chrcteristics. Blood pressure nd nthropometrics mesurements were performed. Fsting venous smples were collected nd PTH nd 25- hydroxyvitmin D were mesured. VitD dequcy ws clssified ccording to the Institute of Medicine, nd MetS ws clssified ccording to the Joint Interim Sttement recommendtions. Multiple liner regression nd unconditionl logistic regression models were used to estimte the ssocitions between the levels of PTH nd 25-hydroxyvitmin D nd with MetS nd its individul components. Results: The prevlence of VitD deficiency ws 37.7%, nd MetS ws present in 191 prticipnts (38.4%). The serum PTH levels showed positive ssocition (OR: 1.014; 95%CI: 1.002, 1.026) with the wist circumference component of MetS. The serum 25-hydroxyvitmin D levels were negtively ssocited with MetS (OR: 0.957; 95%CI: 0.922, 0.993) s well s with its blood pressure (OR: 0.949; 95%CI: 0.912, 0.987) nd triglycerides (OR: ; 95%CI: 0.892, 0.969) components. Conclusion: This study showed high ntionl prevlence of hypovitminosis D. The PTH levels showed significnt positive ssocition with the WC component of MetS, nd the VitD levels were negtively ssocited with the BP nd triglycerides components s well s with the MetS. Keywords: Vitmin D, PTH, Functionl hypoprthyroidism, Metbolic syndrome, Crdiovsculr risk, Prevlence, Portugl Bckground Vitmin D (VitD) is ft-soluble vitmin tht is involved in the metbolism of clcium nd skeletl homeostsis [1]. Choleclciferol (VitD3), the min source of VitD, is synthesized in the skin from the cholesterol precursor * Correspondence: luisrposoendo@gmil.com 1 Grupo de Estudo d Insulino-Resistênci, Sociedde Portugues de Endocrinologi, Dibetes e Metbolismo, Lisbo, Portugl 2 EPIUnit - Instituto de Súde Públic d Universidde do Porto (ISPUP), Porto, Portugl Full list of uthor informtion is vilble t the end of the rticle 7-dehydrocholesterol through exposure to ultrviolet (UV) B rdition. VitD from dietry sources nd sun exposure is not biologiclly ctive nd must undergo two hydroxyltions in the humn body for ctivtion. VitD is first hydroxylted by the liver to form 25-hydroxyvitmin D [25(OH)D], lso known s clcidiol, which is then primrily hydroxylted by the kidney to form the physiologiclly ctive 1α,25(OH) 2 D, or clcitriol. Clcidiol hs low bioctivity but is the min form of VitD in the blood strem nd best indictor of VitD sttus. The Author(s) Open Access This rticle is distributed under the terms of the Cretive Commons Attribution 4.0 Interntionl License ( which permits unrestricted use, distribution, nd reproduction in ny medium, provided you give pproprite credit to the originl uthor(s) nd the source, provide link to the Cretive Commons license, nd indicte if chnges were mde. The Cretive Commons Public Domin Dediction wiver ( pplies to the dt mde vilble in this rticle, unless otherwise stted.

2 Rposo et l. BMC Endocrine Disorders (2017) 17:71 Pge 2 of 10 According to recent review [2], estimtes of the VitD sttus in severl Europen countries showed lrge vritions. No ntionl popultion-bsed study hs been published, nd the only vilble Portuguese studies involved regionl or specific groups using hospitl-bsed recruitment. According to recent study in Portuguese hospitlized ptients, VitD deficiency or indequcy ws present in 60.3% of these ptients [3]. An indequte VitD sttus my ply significnt role in crdiovsculr disese (CVD) risk [4], nd severl observtionl studies suggest n ssocition between hypovitminosis D nd metbolic syndrome (MetS), which represents cluster of interrelted risk fctors for CVD [5]. In ddition, MetS is highly prevlent in Portugl. [6] An evlution of the potentil ssocitions of MetS nd its individul components with VitD levels my support nd enhnce current knowledge of the effects of VitD on CVD risk fctors. Prthyroid hormone (PTH), hormone with close regultory reltionship with VitD, hs lso been ssocited with CVD events [7]. Findings from popultionbsed cross-sectionl studies hve suggested positive ssocition between PTH nd MetS mong older men [8] nd in morbidly obese individuls [9]. The gol of our study ws to evlute the prevlence of hypovitminosis D nd its determinnts s well s PTH serum levels determinnts nd ssocitions of the 25(OH)D nd PTH serum levels with MetS nd its individul components in smple of the Portuguese minlnd popultion. Methods PORMETS (PORtuguese METbolic Syndrome) is ntionl cross-sectionl study tht includes smple of dults registered in primry helth cre centers of the Portuguese minlnd. Informtion regrding PORMETS recruitment proceedings nd methodology hve been previously published by the uthors [10]. According to ntionl legisltion, ll citizens re enrolled in the helth center of their zone of residence. In ech of the eighteen Portuguese minlnd dministrtive regions (districts), two helth cre centers were included. One ws in the district s cpitl nd the other represented non-urbn re. In ech center, prticipnts were rndomly selected from the generl prctitioners lists, nd 120 prticipnts were evluted under n inclusion criterion of 18 yers of ge or older. The selected prticipnts went to the helth center specificlly to prticipte in the study. A totl of 4105 prticipnts were evluted, nd informtion ws collected from Februry 2007 to July Ten prticipnts were excluded from dt nlysis becuse they were pregnnt t the time of the interview. Therefore, 4095 prticipnts remined. For this prticulr study, 500 prticipnts (286 women nd 214 men) were rndomly selected from the initil PORMETS smple. This sub-smple size ws clculted considering mrgin of error of 5%, confidence level of 95% nd response distribution of 50% for the proportion of prticipnts with 25(OH)D levels below 30 ng/ml (75 nmol/l). The comprison between the selected nd unselected prticipnts did not show significnt differences, except for systolic blood pressure nd for insulin serum levels (Tble 1). The PORMETS study ws pproved by the Portuguese Regionl Helth Administrtions, the Ethics Committee of the São João Hospitl E.P.E. nd the Portuguese Dt Protection Authority. Additionlly, pprovl from ech Clinicl Director of the helth cre centers ws received, nd ll prticipnts provided written informed consent. A structured questionnire ws dministered to collect informtion on personl medicl histories nd sociodemogrphic nd behviorl chrcteristics. The prticipnts were considered current smokers if they smoked dily or occsionlly, former smokers if they hd stopped smoking for t lest 6 months, nd non-smokers if they hd never smoked. Regrding lcohol intke, prticipnts were ctegorized s occsionl drinkers if they hd less thn one drink per dy, dily drinkers if they consumed t lest one drink per dy, former drinkers if hd stopped drinking for t lest 6 months nd non-drinkers if they hd never consumed ny type of lcoholic beverge. Regulr physicl exercise ws considered when the prticipnt ws engged in some leisure time physicl ctivity on repeted bsis for t lest 30 min week. Prticipnts who were evluted in the June November period nd December My period were clssified, respectively, s higher nd lower UV rdition exposure. Anthropometrics mesurements were performed, including weight, height (Ht) nd wist (WC) nd hip (HC) circumferences. Weight ws mesured to the nerest 0.1 kg using digitl scle, nd Ht ws mesured to the nerest centimeter in the stnding position using wll stdiometer. WC ws mesured midwy between the bottom of the rib cge nd ilic crest, nd HC ws mesured s the mximum circumference of the buttocks. The wist-to-height rtio (WHtR) ws clculted s the WC divided by the Ht, nd the wist-to-hip rtio (WHR) ws clculted s the WC divided by the HC. Body mss index (BMI) ws clculted s weight in kilogrms divided by the squre of Ht in meters, nd prticipnts were clssified ccording to the World Helth Orgniztion criteri [11]: underweight, norml rnge, pre-obese nd obese ctegories, which re defined s BMI < 18.5 kg/m 2, 18.5 to <25 kg/m 2, 25 to <30 kg/m 2 nd 30 kg/m 2, respectively.

3 Rposo et l. BMC Endocrine Disorders (2017) 17:71 Pge 3 of 10 Tble 1 Comprison between selected nd unselected prticipnts Vribles Unselected prticipnts Selected prticipnts p vlue Gender (n) Women Men Age yers [medin (P25, P75)] 54 (41, 66) 53 (41, 67) Eduction level yers [medin (P25, P75)] 4 (4, 10) 6 (4, 10) Alcohol intke (n) Non-drinker Former drinker Occsionl drinker Dily drinker Smoking hbits (n) Non-smoker Former smoker Smoker Physicl exercise (n) No Yes UV exposure (n) Lower Higher Weight cm [medin (P25, P75)] 71.0 (62.5, 80.5) 71.0 (61.0, 80.0) Height cm [medin (P25, P75)] (155.5, 169.0) (155.0, 169.0) BMI Kg/m 2 [medin (P25, P75)] 27.0 (24.0, 30.0) 27.1 (24.1, 29.8) WC cm [medin (P25, P75)] 93.4 (85.0, 101.5) 93.5 (86.0, 102.0) Systolic BP mmhg [medin (P25, P75)] 130 (116, 145) 131 (119, 147) Distolic BP mmhg [medin (P25, P75)] 79 (70, 86) 80.0 (70, 87) Glucose mg/dl [medin (P25, P75)] 85 (77, 97) 85 (77, 97) Insulin - μu/ml [medin (P25, P75)] 7.6 (5.1, 11.4) 8.0 (5.3, 12.2) HOMA medin (P25, P75) 1.6 (1.0, 2.6) 1.7 (1.1, 2.9) hs-crp - mg/l [medin (P25, P75)] 0.15 (0.07, 0.36) 0.16 (0.08, 0.39) Cholesterol mg/dl [medin (P25, P75)] 206 (179, 233) 204 (180, 233) Triglycerides mg/dl [medin (P25, P75)] 106 (78, 147) 104 (76, 143) HDL-cholesterol mg/dl [medin (P25, P75)] 47 (39, 55) 47 (39, 55) MetS (n) No Yes BP component (n) No Yes WC component (n) No Yes

4 Rposo et l. BMC Endocrine Disorders (2017) 17:71 Pge 4 of 10 Tble 1 Comprison between selected nd unselected prticipnts (Continued) Vribles Unselected prticipnts Selected prticipnts p vlue Glycemi component (n) No Yes HDL-cholesterol component (n) No Yes Triglycerides component (n) No Yes SD stndrd devition, UV ultrviolet, BMI body mss index, WC wist circumference, BP blood pressure, HOMA homeosttic model ssessment, hs-crp high sensitivity C-rective protein, MetS metbolic syndrome Chi-squre test/fisher s exct test or Mnn-Whitney U test p vlue Blood pressure (BP) ws mesured on single occsion using stndrd mercury sphygmomnometer with the cuff on the right upper rm fter 10-min rest. Two BP redings were tken nd the men of the two redings ws clculted. If the difference between the two mesurements ws greter thn 5 mmhg for the systolic or the distolic BP, third mesurement ws tken nd the men of the two closest vlues ws registered. Fsting venous blood smples were collected by trined nurses in ech helth cre center, nd the smples were stored t 80 C. A chemiluminescent immunossy using Liison utomted nlyzer (Disorin Iberi, Mdrid, Spin) ws used to mesure 25(OH)D. Biointct PTH nd insulin were determined by n electro-chemiluminescent immunossy using Cobs e411 utomted nlyzer (Roche, Amdor, Lisbo, Portugl). High sensitivity C- rective protein (hs-crp) ws mesured using prticleenhnced immunonephelometric ssy on BN II lser nephelometer. (Siemens Helthcre, Amdor, Lisbo, Portugl). All other prmeters (glucose, totl cholesterol, triglycerides, HDL-cholesterol, clcium, phosphorus, lbumin nd cretinine) were mesured using conventionl methods with n Olympus AU5400 utomted clinicl chemistry nlyzer. (Beckmn-Coulter,- Oeirs, Lisbo, Portugl). Insulin resistnce ws estimted by the Homeosttic Model Assessment (HOMA), from fsting glucose (mmol/l) nd insulin (μui/ml), s the product of the two divided by VitD dequcy ws clssified ccording to the Institute of Medicine (IOM) recommended cut-off vlues for 25(OH)D levels [12]: deficiency below 12 ng/ml (30 nmol/l); indequcy 12 nd <20 ng/ml ( 30 nd <50 nmol/l) nd sufficiency 20 ng/ml ( 50 nmol/l). Hyper- nd hypoprthyroidism were defined s PTH levels bove nd below the stndrd lbortory reference rnge (10 65 pg/ml), respectively, nd blunted PTH response ws defined s PTH level within the reference rnge in the presence of 25(OH)D 12 ng/ml (30 nmol/l) [13]. MetS ws defined ccording to the Joint Interim Sttement [14] nd ws considered to be present if t lest three (ny) of the following chrcteristics were present: fsting glucose 100 mg/dl or drug tretment for elevted glucose; systolic BP 130 nd/or distolic BP 85 mmhg or ntihypertensive drug tretment in ptient with history of hypertension; triglycerides 150 mg/dl (1.7 mmol/l) or drug tretment for elevted triglycerides; HDL cholesterol <50 mg/dl (1.3 mmol/l) in women nd <40 mg/dl (1.0 mmol/l) in men or drug tretment for reduced HDL-cholesterol; WC 88 cm in women nd 102 cm in men ( Europen criteri). Sttisticl nlysis: Quntittive dt re described s the medin vlues nd corresponding 25th (P25) nd 75th (P75) percentiles. Counts nd proportions were reported for ctegoricl vribles. Proportions were compred using the chi-squre test or Fisher s exct test when pproprite. Mnn-Whitney U test ws used to compre differences between two independent groups. Multiple liner regression models, with the PTH nd 25(OH) D levels s dependent vribles, were used to clculte the regression coefficients nd their respective 95% confidence intervls (95%CI) of severl independent vribles, including gender, ge, level of eduction, drinking nd smoking hbits, UV rdition exposure, physicl exercise, Ht, weight, BMI, WC, HC, WHR, WHtR, systolic nd distolic BP, glucose, triglycerides, HDL-cholesterol, totl cholesterol, insulin, HOMA, hs-crp, lbumin, clcium, phosphorus nd cretinine. The finl model ws djusted for ge nd sex. Unconditionl logistic regression models with MetS, its individul components or blunted PTH response s dependent vribles were computed, nd the odds rtios (OR) nd their respective 95% CI were estimted fter djustments for confounding vribles.

5 Rposo et l. BMC Endocrine Disorders (2017) 17:71 Pge 5 of 10 Results with two-tiled p vlue <0.05 were considered sttisticlly significnt. Sttisticl nlysis ws performed using SPSS version 22 softwre. Results A totl of 500 prticipnts (286 women nd 214 men) with medin ge (P25, P75)) of 53 (41, 67) yers [52 (40, 66) yers in women nd 56 (45, 68) yers in men] were included in the present nlysis. The smple chrcteristics of the 500 prticipnts re presented in Tble 2. The medin 25(OH)D level ws 13.8 ng/ml, with mximum vlue of 43.5 ng/ ml. According to the VitD dequcy ctegories, deficiency ws present in 37.7% of prticipnts, indequcy ws identified in 47.9% of prticipnts nd sufficiency ws determined in 14.4% of prticipnts. A sesonl vrition of serum 25(OH)D ws observed, with significntly higher medin vlues in June November period compred to the December My period (p 0.001). The medin serum PTH level ws 38.1 pg/ml, nd hypo- nd hyperprthyroidism were present in 0.8% nd 9.4% of the prticipnts, respectively. A blunted PTH response ws present in 89.2% of the 185 prticipnts, with serum 25(OH)D levels of less thn or equl to 12 ng/ml (Tble 3). A blunted PTH response ws more frequent in men (OR: 4.100; 95%CI: 1.289, ), nd the frequency decresed with ge (OR: 0.960; 95%CI: 0.930, 0.992). Furthermore, prticipnts with blunted PTH response hd significntly higher serum phosphorus levels (OR: 4.590; 95%CI: 1.425, ) nd lower hs-crp levels (OR: 0.493; 95%CI: 0.258, 0.943). The ssocitions of the PTH nd 25(OH)D levels with vrious socio-demogrphic, behviorl nd clinicl chrcteristics re presented in Tble 4. The serum levels of PTH nd 25(OH)D showed no significnt ssocition between them (p = 0.770). Tble 2 Smple chrcteristics of the 500 prticipnts Totl Women Men p vlue Age (yers) - medin (P25, P75) 53 (41, 67) 52 (40, 66) 56 (45, 68) (OH)D (ng/ml) - medin (P25, P75) 13.8 (9.7,17.6) 13.8 (9.7, 17.5) 13.7 (9.9, 17.9) (OH)D (ng/ml) / UV exposure - medin (P25, P75) Low UV 13.4 (9.3, 17.5) 13.4 (9.3, 16.6) 13.2 (9.0, 17.9) High UV 14.3 (10.0, 18.3) b 14.1 (9.9, 18.6) 14.5 (10.2, 17.6) VitD dequcy - n (%) Deficiency 181 (37.7) 102 (37.5) 79 (38.0) Indequcy 230 (47.9) 133 (48.9) 97 (46.6) Sufficiency 69 (14.4) 37 (13.6) 32 (15.4) PTH (pg/ml) - medin (P25, P75) 38.1 (29.8, 49.2) 38.6 (29.8, 50.1) 37.8 (30.0, 47.7) Blunted PTH response n (%) No 20 (10.8) 16 (15.4) 4 (4.9) Yes 165 (89.2) 88 (84.6) 77 (95.1) PTH sttus n (%) Hypoprthyroidism 4 (0.8) 0 (0) 4 (1.9) Norml sttus 449 (89.8) 254 (88.8) 195 (91.1) Hyperprthyroidism 47 (9.4) 32 (11.2) 15 (7.0) BMI clssifiction - n (%) Underweight 6 (1.2) 5 (1.7) 1 (0.5) Norml rnge 159 (31.9) 94 (32.9) 65 (30.5) Pre-obese 213 (42.7) 113 (39.5) 100 (46.9) Obese 121 (24.2) 74 (25.9) 47 (22.1) Metbolic syndrome - n (%) No 307 (61.6) 169 (59.3) 138 (64.8) Yes 191 (38.4) 116 (40.7) 75 (35.2) SD stndrd devition, 25(OH)D 25-hydroxyvitmin D, VitD vitmin D, UV ultrviolet, low UV period December My, high UV period June November, PTH prthyroid hormone, BMI body mss index Chi-squre test/fisher s exct test or Mnn-Whitney U test p vlue; b p vlue <0.001 for the comprison of the men levels of 25(OH)D ccording to meteorologicl periods

6 Rposo et l. BMC Endocrine Disorders (2017) 17:71 Pge 6 of 10 Tble 3 Blunted PTH response chrcteristics Crude OR (95% CI) OR (95% CI) Gender Women Men (1.122,10.917) (1.289,13.036) Age (0.933,0.996) (0.930,0.992) Height (1.006,11.125) (0.925,1.085) BMI (0.868,1.010) (0.889,1.037) Systolic BP (0.962,1.000) (0.958,1.006) Clcium (0.223,5.825) (0.211,5.486) Phosphorus (1.173,8.615) (1.425,14.781) Albumin (1.050,1.341) (0.998,1.299) Insulin (0.909,1.036) (0.906,1.036) HOMA (0.979,1027) (0.964,1.044) hs-crp (0.250, 0.892) (0.258,0.943) Some of the vribles without significnt ssocitions were excluded from the tble: eduction level, drinking nd smoking hbits, physicl exercise, UV exposure,weight,hipndwistcircumferences,whr,whtr,distolicbp, glucose, triglycerides, HDL-cholesterol, totl cholesterol, cretinine, nd 25(OH)D OR odds rtio, CI confidence intervl, BMI body mss index, BP blood pressure, HOMA homeosttic model ssessment, hs-crp high sensitivity C-rective protein OR djusted for gender nd ge Tble 4 Associtions of PTH nd 25(OH)D with socio-demogrphic, nthropometric, clinicl nd nlyticl chrcteristics Gender Women PTH 25(OH)D β (95% CI) b p vlue β (95% CI) b p vlue Men ( 6.415, 0.246) ( 0.666,1.433) Age (yers) (0.225,0.415) < ( 0.061,0.003) UV exposure Low UV High UV ( 2.541,3.603) ( 0.105,1.985) Physicl exercise No Yes ( 5.799,1.087) (0.484,2.826) BMI (0.143,0.807) ( 0.262, 0.037) WC (0.048,0.320) ( 0.085,0.008) Glucose ( 7.704,3.066) ( 3.903, 0.199) Triglycerides ( 3.557,1.322) ( 2.139, 0.505) Clcium ( 7.923,3.727) ( 1.690,2.286) Phosphorus ( 7.567, 1.812) ( 0.748,1.238) Cretinine (5.267,23.838) ( 0.789,5.522) PTH ( 0.034,0.025) (OH)D ( 0.311,0.230) Some of the vribles without significnt ssocitions were excluded from the tble: level of eduction, drinking nd smoking hbits, height, weight, hip circumference, WHR, WHtR, systolic nd distolic BP, HDL-cholesterol, totl cholesterol, lbumin, insulin, HOMA nd hs-crp CI confidence intervl, UV Ultrviolet, low UV period December My, high UV period June November, IMC body mss index, WC wist circumference, PTH prthyroid hormone serum levels, 25(OH)D 25-hydroxyvitmin D serum levels Reference clss b β coefficients djusted for gender nd ge The serum PTH levels were significntly lower in men (β: ; 95%CI: , 0.246) nd were positively ssocited with ge (β: 0.320; 95%CI: 0.225, 0.415). In ddition, positive ssocitions between PTH nd BMI (β: 0.475; 95%CI: 0.143, 0.807), WC (β: 0.184; 95%CI: 0.048, 0.320) nd cretinine levels (β: ; 95%CI: 5.267, ) were found. Furthermore, negtive ssocition between PTH nd serum phosphorus levels (β: ; 95%CI: , 1.812) ws observed. The serum 25 (OH)D levels were positively ssocited with prticiption in physicl exercise (β: 1.655; 95%CI: 0.484, 2.826) nd were negtively ssocited with BMI (β: ; 95%CI: , 0.037) nd serum glucose (β: ; 95%CI: , 0.199) nd triglycerides (β: ; 95%CI: , 0.505) levels. MetS ws present in 191 prticipnts (38.4%), nd its prevlence ws slightly higher in women thn in men, but without sttisticl significnce (40.7% versus 35,2%, p = 0.213). The MetS prevlence significntly incresed with ge (p < 0.001) nd with higher HOMA scores (p < 0.001) s well s higher insulin (p < 0.001) nd hs-crp (p = 0.027) levels. Tble 5 shows the ssocitions of PTH nd 25(OH)D with MetS nd its individul components. The PTH serum levels showed crude positive ssocition with MetS (OR: 1.016; 95%CI: 1.006, 1.027) nd its WC (OR: 1.023; 95%CI: 1.012, 1.034) nd BP (OR: 1.022; 95%CI: 1.010, 1.034) fetures. After djustments for ge nd sex (model 1), only the ssocition with the WC feture remined significnt. This ssocition remined significnt even fter further djustment for 25(OH)D levels (OR: 1.013; 95%CI: 1.001, 1.015). After djustment for ge, sex nd BMI (model 2), this ssocition lost sttisticl significnce. We lso found crude negtive ssocition between the serum 25 (OH) D levels nd MetS (OR: 0.953; 95%CI: 0.921, 0.985) nd its BP (OR: 0.951; 95%CI: 0.920, 0.983) nd triglycerides (OR: 0.930; 95%CI: 0.893, 0.969) components. After djustments for ge nd sex (model 1), ll the three ssocitions remined significnt. However, fter further djustment for BMI (model 2), the ssocition remined sttisticlly significnt only for the BP nd triglycerides components of the MetS [(OR: 0.954; 95%CI: 0.916, 0.993) nd (OR: 0.937; 95%CI: 0.898, 0.978), respectively]. Discussion VitD sttus We found high prevlence of VitD deficiency or indequcy (85.6%) in this smple of the Portuguese popultion. The high prevlence is supported by previously published ntionl evidence (VitD deficiency or indequcy rnging from 60.3% to 92.7%), lthough specific popultion groups were recruited in hospitl settings

7 Rposo et l. BMC Endocrine Disorders (2017) 17:71 Pge 7 of 10 Tble 5 Associtions of PTH nd 25 (OH) D with MetS nd its components PTH 25(OH)D Model 1: OR (95% CI) Model 2: OR (95% CI) Model 1: OR (95% CI) Model 2: OR (95% CI) MetS (0.993,1015) (0.983,1.008) (0.922,0.993) (0.930,1.007) WC (1.002,1.026) (0.986,1.017) (0.958,1.026) (0.980,1.069) BP (0.992,1.020) (0.988,1.016) (0.912,0.987) (0.916,0.993) Trig (0.983,1.008) (0.978,1.004) (0.892,0.969) (0.898,0.978) HDL (0.988,1.009) (0.985,1.006) (0.959,1.023) (0.965,1.030) Glu (0.985,1.010) (0.981,1.007) (0.936,1.016) (0.949,1.033) OR odds rtio, CI confidence intervl, PTH prthyroid hormone serum levels, 25(OH)D 25-hydroxyvitmin D serum levels, MetS metbolic syndrome, WC wist circumference component, BP blood pressure component, Trig triglycerides component, HDL HDL cholesterol component, Glu glucose component Model 1: OR djusted for gender nd ge; Model 2: OR djusted for gender, ge nd body mss index OR (95%CI) fter djustment for gender, ge nd 25(OH)D serum level: (1.001, 1.025) [3, 15, 16]. In ddition, ccording to recent study, conducted in the city of Porto [17], which included 198 helthy prticipnts, VitD deficiency or indequcy ws present in 48%. In the winter period, these vlues reched 74%. Compred with other Europen [2] nd worldwide [18] popultions, the medin 25(OH)D levels observed in this study were reltively low despite the fvorble ltitude. The high prevlence of pre-obesity nd obesity my hve contributed to these figures. Furthermore, VitD intke in the Portuguese popultion is reltively low [2]. Food fortifiction, VitD supplementtion, sunlight exposure nd UV protection hbits my lso be contributing fctors to the differences observed cross vrious countries. Severl Europen countries hve dopted mesures t the ntionl level to implement VitD supplementtion nd food fortifiction policies, but they re not hrmonized cross Europe [2]. In ddition, dietry reference vlues for VitD intke hve been subject of debte in some countries. In Portugl, there is no legisltion of food fortifiction nd VitD supplementtion ( IU/dy) in dults is only recommended for elderly popultions (> 65 yers) nd subjects with osteoporosis, osteopeni or those with mjor risk for osteoporosis [19]. Functionl hypoprthyroidism nd the ssocition between VitD nd PTH Despite ll of the complex interreltionships, no significnt ssocition between PTH nd 25(OH)D ws observed. This lck of ssocition ws previously reported [20] nd my be prtly explined by blunted PTH response to VitD deficiency [13]. In fct, most prticipnts with Vit D deficiency hd blunted PTH response (89.2%). This response cnnot be explined by the type of definition of hypovitminosis D used (IOM) becuse ccording to its definition only prticipnts with serum levels of 25 (OH) D lower thn 12 ng/ml nd with norml serum PTH levels were considered. The blunted PTH response my correspond to protective mechnism of bone mss, through the development of functionl hypoprthyroidism [13]. In ddition to prthyroid dysfunction, other fctors my contribute to the modifiction of the PTH response to low VitD levels [21 23], such s ge, gender, BMI, kidney dysfunction, smoking, nd serum clcium levels. Our results did not show significnt contribution of smoking, BMI nd serum levels of clcium nd cretinine to the blunted PTH response, but we found positive ssocitions with mle gender nd serum phosphorus levels nd negtive ssocitions with ge nd serum levels of hs-crp. A positive ssocition ws lredy described between PTH nd hs-crp serum levels [24]. In ddition to the blunted PTH response, other fctors my hve contributed to the lck of ssocition between the PTH nd 25(OH)D levels. The method of mesurement strongly influences the VitD nd PTH levels nd my modify the reltionship between them. Specificlly, the chemiluminescent immunossy my hve underestimted the 25(OH)D mesurements [25]. Regrding the third genertion PTH ssy, freezing my hve contributed to reduced PTH levels [26]. However, previous studies on 25(OH)D showed gret stbility under freezing conditions [27]. Moreover, despite being useful biomrker of VitD supply to trget tissues, 25(OH)D my not be good functionl mrker of the biologiclly ctive form, 1α,25(OH) 2 D, reltive to PTH regultion. Finlly, the upper reference vlue of norml serum PTH levels (65 pg/ml) tht is usully used my not be pproprite s cut-off point for the definition of high PTH levels [13, 21]. VitD, PTH nd MetS ssocitions To the best of our knowledge, this is the first ntionl study to evlute 25(OH)D nd PTH levels nd their ssocitions with MetS. According to our dt, MetS prevlence ws high nd incresed with ge, HOMA score, nd insulin nd hs-crp levels (dt not shown). These results re supported by previous studies [28].

8 Rposo et l. BMC Endocrine Disorders (2017) 17:71 Pge 8 of 10 Our study showed significnt positive ssocition between PTH nd ge even fter djusting for sex. By contrst, no significnt ssocition between 25(OH)D nd ge ws observed. According to systemtic review, PTH levels re positively correlted with ge [23]. We lso found significnt negtive ssocition between serum PTH levels nd mle gender [29]. Although higher PTH levels hve been ssocited with incresed risk of CVD [7], insulin resistnce, blood pressure nd obesity [8, 9] we did not find significnt ssocition between MetS nd PTH levels in the djusted model. Others hve found positive ssocition between PTH nd MetS only mong older men [8] nd in morbidly obese individuls [9]. We found positive ssocitions of PTH serum levels with BMI, WC nd the WC component of MetS. As expected, the ssocition with the WC component of MetS ws lost fter further djustment for BMI. The link between PTH levels nd incresed body ft is supported by the evidence of incresed body weight in primry hyperprthyroidism [30] nd by the positive ssocition with BMI [31]. This ssocition my be even stronger in viscerl dipose tissue [32], explining the stronger correltion found with WC. PTH my increse dipose mss, especilly in the viscerl comprtment, by incresing the influx of clcium into dipocytes. The 25 (OH) D levels showed positive ssocition with prticiption in physicl exercise, which persisted fter djusting for sex nd ge. Regulr outdoor physicl ctivity is ssocited with higher levels of serum VitD [33], which cn be prtly explined by higher UV rdition exposure. Unfortuntely, in this study, no dt were vilble on the specific type of exercise prcticed by the prticipnts in our smple (indoor versus outdoor). MetS ws inversely ssocited with 25(OH)D levels even fter djusting for ge nd sex; however, the ssocition ws lost fter further djustment for BMI. A recent met-nlysis showed tht the prevlence of MetS decresed t higher 25(OH)D concentrtions [5]. In ddition, the prevlence of hypovitminosis D is generlly incresed in dults with CVD, nmely in coronry hert disese nd hert filure [34], nd low 25(OH)D levels re ssocited with n incresed risk of ischemic hert disese, myocrdil infrction, nd premture deth [4]. Furthermore, results from recent met-nlysis indicte non-liner decrese in overll mortlity s the 25(OH)D levels increse [35]. Low levels of vitmin D hve been reported to be ssocited not only with obesity nd insulin resistnce but lso with glucose intolernce, dyslipidemi, incresed renin gene trnscription, endothelil dysfunction, prolifertion of vsculr smooth muscle cells, thrombogenecity nd inflmmtion [5]. However, low levels of vitmin D my be simply secondry to inflmmtion nd other phenomen ssocited with obesity nd insulin resistnce. We found significnt positive ssocition of the 25(OH)D levels with BMI, but not with the WC nd WC components of MetS. A bi-directionl Mendelin rndomiztion nlysis [36] suggested cusl role of obesity for the risk of hypovitminosis D. However, ny cusl effect of hypovitminosis D in obesity is likely to be smll. The possible mechnisms for the lower 25(OH) D concentrtions in obesity [37] include: lower VitD dietry intke, reduced sunbthing hbits due to decresed willingness to expose the body, sedentry lifestyle nd mobility limittions, decresed biovilbility due to sequestrtion in the dipose tissue nd volumetric dilution effect relted to greter body weight. A negtive ssocition of 25(OH)D with glycemi ws observed, but not with the glycemic component of MetS. Severl longitudinl cohort studies nd recent metnlysis [38] demonstrted n inverse ssocition between the 25(OH)D levels nd incresed risk of type 2 dibetes. VitD sttus cn interfere with insulin secretion nd insulin resistnce. VitD stimultion of β-cell VDRs nd locl ctivtion of the 1-α-hydroxylse enzyme my contribute to the modultion of pncretic β-cells clcium influx nd insulin synthesis. VitD my lso increse insulin sensitivity by incresing insulin receptor expression nd by stimulting insulin-induced glucose trnsport. A negtive ssocition ws present between the 25(OH)D levels nd triglycerides levels [39] nd triglycerides component of MetS. Although the mechnisms re not cler, they my involve metbolism of triglycerides through modultion of the intrcellulr clcium content of dipocytes nd heptocytes. Hypovitminosis D-relted inflmmtion nd insulin resistnce my be other contributing fctors. Although no liner ssocition ws found between distolic or systolic BP nd the 25(OH)D levels (dt not shown), the 25(OH)D levels showed significnt ssocition with the BP component of MetS. According to the literture, VitD is inversely ssocited with BP [40], nd severl mechnisms hve been proposed to be relted to hypovitminosis D nd hypertension [41], including disruption of the negtive endocrine regultion of renin gene expression, secondry hyperprthyroidism, nd enhnced vsculr tone through direct or indirect dysfunction of the endothelil nd vsculr smooth muscle cells. Also, the ssocitions observed between Mets nd its individul components nd PTH nd 25 (OH) D serum levels were generlly wek. In fct, this ws not surprising s the vribles considered in those ssocitions were continuous nd therefore the clculted ORs represent the odds of n outcome occurring for n incresed unit of PTH or 25(OH)D serum levels.

9 Rposo et l. BMC Endocrine Disorders (2017) 17:71 Pge 9 of 10 Lstly, one must cknowledge some dditionl limittions of this study. Firstly, due to its cross-sectionl nture, no cusl reltion cn be inferred from the significnt ssocitions observed. Also, nd finlly, one could expect type I error in the evlution of the crude ssocitions due to multiple comprisons. Nevertheless, the uthors do not expect tht this could hve occurred in the finl model defined for this study, s the number of tested vribles ws in fct smll. Conclusion The present study showed high prevlence of hypovitminosis D in smple of the Portuguese popultion. Compred with other Europen nd worldwide popultions, our medin level of 25(OH)D (13.8 ng/ml) is reltively low. The prevlence of hypovitminosis D ws higher in prticipnts with higher BMI nd sedentry lifestyles. The PTH levels showed significnt positive ssocition with BMI, WC nd the WC component of MetS, suggesting possible role in the pthophysiology of obesity. The 25(OH)D levels were negtively ssocited with BMI, glucose nd triglycerides levels s well s with MetS nd its BP nd triglycerides components, indicting tht hypovitminosis D my contribute to the pthophysiology of MetS. Considering the low levels nd indequte intke of VitD, the frequency of overweight, nd potentilly insufficient solr exposure in the Portuguese popultion, it is crucil to develop ntionl policies to increse wreness of the importnce of VitD for helth nd to develop strtegies for the identifiction of vitmin D deficiency, especilly in t-risk groups. Abbrevitions 25(OH)D: 25-hydroxyvitmin D; BMI: Body mss index; CI: Confidence intervl; CVD: Crdiovsculr disese; HC: Hip circumference; HOMA: Homeosttic model ssessment; hs-crp: High sensitivity C-rective protein; Ht: Height; MetS: Metbolic syndrome; OR: Odds rtio; PTH: Prthyroid hormone; SD: Stndrd devition; UV: Ultrviolet; VitD: Vitmin D; VitD3: Choleclciferol; WC: Wist circumference; WHR: Wist-to-hip rtio; WHtR: Wist-to-height rtio Acknowledgements The uthors would like to thnk ll PORMETS cohort-prticipnts, logistic stff nd scientists for their contribution to the study. Funding This work ws supported by the Insulin Resistnce Study Group of the Endocrinology, Dibetes nd Metbolism Portuguese Society. An Cristin Sntos holds FCT Investigtor contrct IF/01060/2015. Avilbility of dt nd mterils The dtsets used nd nlysed during the current study re vilble from the corresponding uthor on resonble request, once the study hs been published. Authors contributions LR, JTG nd ACS were involved in the conception of the study. LR ws involved in the sttisticl nlysis. SM nd DF were involved in the ccomplishment of the lbortory exms. All uthors were involved in drfting the mnuscript, pproving the finl drft, nd gree to be ccountble for the work. All uthors red nd pproved the finl mnuscript. Ethics pprovl nd consent to prticipte All the Portuguese Regionl Helth Administrtions, the Ethics Committee of the São João Hospitl E.P.E. nd the Portuguese Dt Protection Authority, pproved PORMETS. The Clinicl Director of ech helth cre center lso provided uthoriztion nd ll prticipnts gve their written informed consent. The Ethics Committee of Centro Hospitlr São João (Porto, Portugl) pproved the study in the 27th Februry 2007 nd the uthoriztion from the Portuguese Dt Protection Authority is CNDP: 1053/2007. Consent for publiction Not pplicble. Competing interests The uthors declre tht they hve no competing interests. Publisher s Note Springer Nture remins neutrl with regrd to jurisdictionl clims in published mps nd institutionl ffilitions. Author detils 1 Grupo de Estudo d Insulino-Resistênci, Sociedde Portugues de Endocrinologi, Dibetes e Metbolismo, Lisbo, Portugl. 2 EPIUnit - Instituto de Súde Públic d Universidde do Porto (ISPUP), Porto, Portugl. 3 Serviço de Ptologi Clínic, Centro Hospitlr de S. João, Porto, Portugl. 4 Deprtmento de Biomedicin, Fculdde de Medicin, Universidde do Porto, Porto, Portugl. 5 Deprtmento de Ciêncis d Súde Públic e Forenses e Educção Médic, Fculdde de Medicin, Universidde do Porto, Porto, Portugl. Received: 6 July 2017 Accepted: 12 November 2017 References 1. Verstuyf A, Verlinden L, Crmeliet G, Vitmin D. Metbolism, moleculr mechnism of ction, nd pleiotropic effects. Physiol Rev. 2016;96(1): Spiro A, Buttriss JL, Vitmin D. An overview of vitmin D sttus nd intke in Europe. Nutr Bull. 2014;39: Sntos MJ, Fernndes V, Grci FM, Vitmin D. Insufficiency in hospitl popultion: photogrph from the lbortory perspective. Act Medic Port. 2015;28(6): Brøndum-Jcobsen P, Benn M, Jensen GB, Nordestgrd BG. 25-Hydroxyvitmin D levels nd risk of ischemic hert disese, myocrdil infrction, nd erly deth. Popultion-bsed study nd met-nlyses of 18 nd 17 studies. Arterioscler Thromb Vsc Biol. 2012;32: SY J, Jeong HS, Kim DH, Blood Vitmin D. Sttus nd metbolic syndrome in the generl dult popultion: dose-response met-nlysis. J Clin Endocrinol Metb. 2014;99: Fiuz M, Cortez-Dis N, Mrtins S, Belo A. Metbolic syndrome in Portugl: prevlence nd implictions for crdiovsculr risk - results from the VALSIM study. Rev Port Crdiol. 2008;27: vn Bllegooijen AJ, Reinders I, Visser M, Brouwer IA. Prthyroid hormone nd crdiovsculr disese events: systemtic review nd met-nlysis of prospective studies. Am Hert J 2013;165: Reis JP, von Mühlen D, Miller IIIER. Reltion of 25-hydroxyvitmin D nd prthyroid hormone levels with metbolic syndrome mong US dults. Eur J Endocrinol. 2008;159(1): Hjelmeseth J, Hofsø D, Asheim ET, Jenssen T, Mon J, Hger H, Røislien J, Bollerslev J. Prthyroid hormone, but not vitmin D, is ssocited with the metbolic syndrome in morbidly obese women nd men: cross-sectionl study. Crdiovsc Dibetol. 2009;8:7. doi: / Rposo L, Severo M, Brros H, Sntos AC. The prevlence of the metbolic syndrome in Portugl: the PORMETS study. BMC Public Helth. 2017;17:555. doi: /s WHO Expert Consulttion. Approprite body-mss index for Asin popultions nd its implictions for policy nd intervention strtegies. Lncet. 2004; 363(9403): Dietry Reference Intkes for Clcium nd Vitmin D. Institute of Medicine (US) committee to review dietry reference intkes for vitmin D nd clcium; Ross AC, Tylor CL, Yktine AL, Del Vlle HB, editors. Wshington (DC): Ntionl Acdemies Press (US); The Ntionl Acdemies Collection: Reports funded by Ntionl Institutes of Helth.

10 Rposo et l. BMC Endocrine Disorders (2017) 17:71 Pge 10 of Shot O, Mundey MK, Sn P, Godber IM, Lwson N, Hosking DJ. The reltionship between vitmin D nd prthyroid hormone: clcium homeostsis, bone turnover, nd bone minerl density in postmenopusl women with estblished osteoporosis. Bone. 2004;35: Alberti KG, Eckel RH, Grundy SM, Zimmet PZ, Cleemn JI, Donto KA, Fruchrt JC, Jmes WP, Lori CM, Smith SC Jr. Hrmonizing the metbolic syndrome: joint interim sttement of the interntionl dibetes federtion tsk force on epidemiology nd prevention; Ntionl Hert, Lung, nd Blood Institute; Americn Hert Assocition; world hert federtion; interntionl therosclerosis society; nd Interntionl Assocition for the Study of obesity. Circultion. 2009; 120: Sntigo T, Rebelo M, Porto J, Silv N, Vieir J, Nscimento Cost JM, Hypovitminosis D. In ptients dmitted to n internl medicine Wrd. Act Medic Port. 2012;25(2): Alves M, Bstos M, Leitão F, Mrques GB, Ribeiro G, Crrilho F. Vitmin D importnce of lbortory evlution. Rev port Endocrinol Dibetes Metb. 2013;8(1): Bettencourt A, Boleix D, Reis J, Oliveir JC, Mendonç D, Cost PP, Silv BMD, Mrinho A, Silv AMD. Serum 25-hydroxyvitmin D levels in helthy popultion from the north of Portugl. J Steroid Biochem Mol Biol. 2016; doi: /j.jsbmb Hilger J, Friedel A, Herr R, Rusch T, Roos F, Whl DA, Pierroz DD, Weber P, Hoffmnn KA. Systemtic review of vitmin D sttus in popultions worldwide. Br J Nutr. 2014;111(1): Direção-Gerl d Súde. Orientção técnic sobre suplementção de cálcio e vitmin D em pessos idoss. Circulr Informtiv n 13/DSCS/DPCD/ DSQC de 01/04/2008 (directorte-generl of helth. Technicl guidnce on clcium nd vitmin D supplementtion in older people. Informtion circulr no.13/dscs/dpcd/dsqc, 1th of April, 2008). directrizes-d-dgs/orientcoes-e-circulres-informtivs.spx?v=bd49e d f56e &cchecontrol= Acessed 15 Nov Kilicrsln A, Asln AC, Gezgen G. The role of vitmin D deficiency in prthyroid hormone levels. Turk J Med Sci. 2013;43(3): Admi S, Vipin O, Gtti D, Idolzzi L, Rossini M. Reltionship between serum prthyroid hormone, vitmin D sufficiency, ge, nd clcium intke. Bone. 2008;42(2): Gunnrsson ö, Indridson S, Frnzson L, Sigurdsson G. Fctors ssocited with elevted or blunted PTH response in vitmin D insufficient dults. J Intern Med. 2009;265: Björkmn M, Sorv A, Tilvis R. Responses of prthyroid hormone to vitmin D supplementtion: systemtic review of clinicl trils. Arch Gerontol Geritr. 2009;48(2): Cheng SP, Liu CL, Liu TP, Hsu YC, Lee JJ. Assocition between prthyroid hormone levels nd inflmmtory mrkers mong US dults. Medit Inflmm. 2014;2014: doi: /2014/ Wllce AM, Gibson S, de l Hunty A, Lmbert-Allrdt C, Ashwell M. Mesurement of 25-hydroxyvitmin D in the clinicl lbortory: current procedures, performnce chrcteristics nd limittions. Steroids. 2010; 75(7): doi: /j.steroids Hnon EA, Sturgeon CM, Lmb EJ. Smpling nd storge conditions influencing the mesurement of prthyroid hormone in blood smples: systemtic review. Clin Chem Lb Med. 2013;51(10): Ocke MC, Schrijver J, Obermnn-de Boer GL, Bloemberg BP, Henen GR, Kromhout D. Stbility of blood (pro)vitmins during four yers of storge t 20 degrees C: consequences for epidemiologic reserch. J Clin Epidemiol. 1995;48: Kur J. A comprehensive review on metbolic syndrome. Crdiol Res Prct. 2014;2014: doi: /2014/ Pik JM, Frwell WR, Tylor EN. Demogrphic, dietry, nd serum fctors nd prthyroid hormone in the Ntionl Helth nd nutrition exmintion survey. Osteoporos Int. 2012;23(6): Bollnd MJ, Grey AB, Gmble GD, Reid IR. Assocition between primry hyperprthyroidism nd incresed body weight: met-nlysis. J Clin Endocrinol Metb. 2005;90: Gusch A, Bulló M, Rbss A, Bond A, Del Cstillo D, Sbench F, Sls-Slvdó J. Plsm vitmin D nd prthormone re ssocited with obesity nd therogenic dyslipidemi: cross-sectionl study. Crdiovsc Dibetol. 2012;11:149. doi: / George JA, Norris SA, Tomn M, Snymn T, Crowther NJ. Viscerl diposity is predictor of prthyroid hormone levels in helthy dults. J Endocrinol Investig. 2016;39: Scrgg R, Cmrgo CA Jr. Frequency of leisure-time physicl ctivity nd serum 25-hydroxyvitmin D levels in the US popultion: results from the third Ntionl Helth nd nutrition exmintion survey. Am J Epidemiol. 2008;168(6): Kim DH, Sbour S, Sgr UN, Adms S, Whelln DJ. Prevlence of hypovitminosis D in crdiovsculr diseses (from the Ntionl Helth nd nutrition exmintion survey 2001 to 2004). Am J Crdiol. 2008;102(11): Zittermnn A, Iodice S, Pilz S, Grnt WB, Bgnrdi V, Gndini S, Vitmin D. Deficiency nd mortlity risk in the generl popultion: met-nlysis of prospective cohort studies. Am J Clin Nutr. 2012;95: Vimleswrn KS, Berry DJ, Lu C, Tikknen E, Pilz S, Hirki LT, et l. Cusl reltionship between obesity nd vitmin D sttus: bi-directionl Mendelin rndomiztion nlysis of multiple cohorts. PLoS Med. 2013;10(2):e doi: /journl.pmed Vnlint S. Vitmin D nd Obesity. Nutrients. 2013;5: Afzl S, Bojesen SE, Nordestgrd BG. Low 25-Hydroxyvitmin D nd risk of type 2 dibetes: prospective cohort study nd metnlysis. Clin Chem. 2013;59(2): Jorde R, Figenschu Y, Hutchinson M, Emus N, Grimnes G. High serum 25- hydroxyvitmin D concentrtions re ssocited with fvorble serum lipid profile. Eur J Clin Nutr. 2010;64(12): Burgz A, Orsini N, Lrsson SC, Wolk A. Blood 25- hydroxyvitmin D concentrtion nd hypertension: met-nlysis. J Hypertens. 2011;29: Chen S, Sun Y, Agrwl DK. Vitmin D deficiency nd essentil hypertension. 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