Case Report. Silent growth hormone secreting pituitary adenomas: IGF-1 is not sufficient to exclude growth hormone excess. Introduction.

Transcription

1 Case Report Silent growth hormone secreting pituitary adenomas: IGF-1 is not sufficient to exclude growth hormone excess S Kalavalapalli 1, H Reid 2, J Kane 3, H Buckler 1, P Trainer 4 and A H Heald 1,5 Abstract Addresses 1 Department of Endocrinology; 2 Department of Cellular Pathology; and 3 Department of Clinical Biochemistry, University of Manchester, Salford NHS Trust, Salford M6 8HD, UK; 4 Department of Endocrinology, University of Manchester, Christie Hospital, Manchester M20 4BX, UK; 5 Department of Medicine, Bishop Auckland General Hospital, Bishop Auckland, Co Durham DL14 6AD, UK Correspondence Dr AH Heald aheald@fs1.ho.man.ac.uk Circulating insulin-like growth factor-1 (IGF-1) is increasingly being used as a screening test and in ongoing monitoring of treated acromegaly. We here present three cases of women (two of whom were on the oestrogen containing contraceptive pill at the time of presentation) who had normal circulating IGF-1 and no overt clinical features of acromegaly at the time of their pituitary surgery. Postoperatively, all were confirmed to have growth hormone excess in keeping with the presence of active somatotroph pituitary adenomas. We suggest that for optimal patient management, formal evaluation of growth hormone status with oral glucose tolerance testing should ideally be performed on all individuals for whom pituitary surgery is planned. Introduction In the absence of suggestive signs and symptoms of endocrine excess, endocrinologists usually rely on basal endocrine tests to exclude a functional pituitary adenoma. The diagnosis of acromegaly is normally based on classical clinical features associated with the growth hormone (GH) excess. 1 Silent somatotroph adenomas are de ned as GH-secreting tumours with no clinical stigmata of GH excess Circulating insulin-like growth factor-1 (IGF-1) is increasingly being used as a screening test and in ongoing monitoring of treated acromegaly We here describe three female patients with pituitary macroadenomas in whom preoperative endocrine assessment showed a normal IGF-1 level with no clinical features suggestive of acromegaly, but who postoperatively were con rmed to have GH excess. We feel that this raises some important issues of relevance to clinical practice. Laboratory methods and neuroimaging Circulating thyroxine, thyroid-stimulating hormone (TSH), luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin were measured at Hope Hospital, Salford, by immunoassay on the Abbott Architect analyser (Abbott Diagnostics, Maidenhead, Berkshire, UK). Growth hormone, cortisol and oestradiol were measured on the Immulite 2000 analyser (DPC, Llanberis, Gwynedd, UK). IGF-1 was determined using the Nichols Advantage (Nichols Institute Diagnostics, San Clemente, California, USA). The limit of sensitivity of the assay was 6 mg/l. Intra-assay coe cient of variation (CV) was between 4.4 and 5.2%, and inter-assay CV between 5.7 and 7.4%. This assay has no signi cant cross-reactivity with IGF-2, insulin or proinsulin. In each case, postoperative endocrine evaluation was performed at six weeks following surgery. Postoperative magnetic resonance imaging was carried out three months following surgery, in line with our standard protocol. Case reports Case 1 A 22-year-old woman was referred to us having been found to have a pituitary macroadenoma on magnetic resonance imaging (MRI) in the course of investigation for grand mal seizures (Figure 1). She had no clinical features of acromegaly. At that time, she had normal baseline pituitary function with a total thyroid hormone (T4) of 149 nmol/l (reference range ), r 2007 The Association for Clinical Biochemistry 89

2 90 Kalavalapalli et al. TSH of 1.45mU/L ( ), a random cortisol of 408 nmol/l and normal IGF-1 of 363 mg/l ( ). She had an elevated prolactin of 1580 mu/l ( ), presumed to be secondary to pituitary stalk compression. She had been taking the oral contraceptive pill (OCP) (TriNovum; Janssen-Cilag, Bucks, UK) for four years with regular withdrawal bleeds. Visual eld assessment showed evidence of left anterior chiasmal compression resulting in a left optic neuropathy and unilateral right temporal visual eld defect. The patient underwent trans-sphenoidal pituitary surgery for the presumed non-functioning pituitary macroadenoma with no postoperative complications. Postoperative endocrine assessment revealed a normal response to Synacthen testing, with basal cortisol at 622 nmol/l rising to 736 nmol/l after 30 min. Thyroid function was normal. However, her IGF-1 four months postoperatively was raised, at 538 mg/l ( ). She had by then discontinued the OCP. Histology and immunohistochemistry con rmed the tumour to be a sparsely granulated somatotroph adenoma. Ki-67 index was in excess of 4%. No prolactin immuno-expression was found. In view of the postoperatively raised IGF-1 and histology ndings, she had measurements of GH in relation to a 75 g oral Pituitary macroadenoma Figure 1 Case 1: Pituitary macroadenoma on sagittal T1 view glucose load, which con rmed GH excess (Table 1). The patient did not have any symptoms or clinical signs of acromegaly. MRI scan showed a signi cant tumour residuum ( cm), and in view of the evidence of excess GH, long-acting somatostatin analogue therapy was initiated. Later, dopamine agonists were also introduced, but remission could not be achieved. The patient underwent repeat trans-sphenoidal pituitary surgery. Histology again showed a sparsely granulated somatotroph adenoma. These are known to take an aggressive clinical course. 10 The patient presently continues with her medical therapy (Octreotide LAR 40 mg every 4 weeks [Novartis Pharmaceutical, UK Ltd., Surrey, UK] and Cabergoline 0.5 mg twice a week [P zer Ltd., Surrey, UK]) and has been referred for radiotherapy, as the acromegaly remains biochemically active. Case 2 A 17-year-old woman presented with visual symptoms of over a year duration and amenorrhoea of over six months duration. She had no galactorrhoea and was not on any medication. On examination, she did not look acromegalic or Cushingoid. She was initially referred to an ophthalmologist who con rmed bitemporal haemianopia. She was found to have a large pituitary macroadenoma of cm on pituitary MRI scan. Initial endocrine investigations showed prolactin of 831mU/L ( ), TSH 2.1mU/L ( ), total T4 51nmol/L ( ), LH 2.4 mu/l, FSH 5.7 mu/l and oestradiol of 81pmol/L. IGF-1 was 175 mg/l ( ) and short synacthen test showed normal adrenocortical reserve. She underwent right pterional craniotomy with debulking of the sellar/suprasellar tumour, following which her vision improved dramatically with no postoperative complications. Histology and immunohistochemistry showed that the majority of tumour cells stained positive for GH, and a signi cant minority Table 1 Postoperative glucose tolerance test results for each patient Time 0 min 30 min 60 min 90 min 120 min 150 min Patient 1 Glucose (mmol/l) Growth hormone (mg/l) Patient 2 Glucose (mmol/l) Growth hormone (mg/l) Patient 3 Glucose (mmol/l) Growth hormone (mg/l)

3 IGF-1 measurement is insufficient to exclude GH excess 91 for prolactin, appearances being consistent with a mammosomatotroph adenoma. Postoperative endocrine assessment showed a normal response to 250 mg of synacthen.her TSH was 0.83 mu/l ( ), free T4 14 pmol/l (9--22), LH 5.1mU/L, FSH 7.3 mu/l with a low oestradiol of 66 pmol/l. IGF-1 was raised at 669 mg/l ( ). In view of the raised IGF-1 postoperatively and GHpositive immunohistochemistry, she had a 75 g oral glucose tolerance test with measurement of GH, the results of which are shown in Table 1. GH was not suppressed. In the light of the signi cant tumour residuum postoperatively, after close consideration of all the options including implications on fertility, she proceeded to have radiotherapy. She was also commenced on somatostatin analogues and was put on the OCP Loestrin 20 (Galen Ltd., Northern Ireland, UK), as she continued to be amenorrhoeic with low gonadotrophins (LH 3.7 mu/l, FSH 9.7 mu/l and oestradiol o73 pmol/l). The most recent endocrine review demonstrated good control of her acromegaly, with IGF-1 of 512 mg/l ( ), free T4 12 pmol/l (9--19) and a normal response to short synacthen testing. The most recent MRI scan revealed a stable residual lesion which is undergoing progressive cystic degeneration. She remains well on her present medications of Octreotide LAR 20 mg once a month along with daily oral Loestrin 20. Case 3 A 24-year-old woman presented with an incidental pituitary macroadenoma detected on MRI when being investigated for possible demyelination. She did not have any clinical features suggestive of acromegaly or Cushing s disease, and she had regular withdrawal bleeds on the oral contraceptive pill (Cilest; Janssen- Cilag, Bucks, UK), which she had been taking for six years, with no history of galactorrhoea. Her initial endocrine investigations showed normal thyroid function, prolactin was 265 mu/l ( ), IGF-1 was normal at 207 mg/l ( ) and random cortisol was 287 nmol/l. An attempt was made to resect the tumour via the transphenoidal route, but the surgery was abandoned due to haemorrhage in the cavernous sinus. Postoperative endocrine evaluation showed a high GH of12.1 mg/l andigf-1wasraisedat 428mg/L ( ). The remainder of the endocrine tests were normal, including thyroid function. Prolactin was 268 mu/l and her cortisol response on insulin tolerance testing (ITT) was normal with cortisol rising to 986 nmol/l. She did not have any clinical features of acromegaly. However, biochemical growth hormone excess was con rmed with a 75 g oral glucose tolerance test, with estimation of GH as shown in Table 1. The patient subsequently underwent a transphenoidal hypophysectomy. The postoperative endocrine testing showed an IGF-1 of 509 mg/l ( ), with inadequate cortisol response (basal cortisol of 140 nmol/l at 0 min remained the same after 30 min of synacthen). The rest of the hormone pro le was normal. The histology was consistent with a mammosomatotroph adenoma. Immunohistochemical examination revealed that GH-reactive cells varied from scarce to approximately 50% in di erent regions of the tumour. Prolactin-positive cells varied from scarce to 35% in di erent regions. Postoperatively, in view of signi cant residual tumour mass and persistently raised IGF-1, she underwent pituitary irradiation. She was started on Thyroxine as she developed clinical and biochemical secondary hypothyroidism and her most recent endocrine status was stable with a normal IGF-1 of 110 mg/l ( ) and a free T4 of 13 pmol/l (9--19). Her latest MRI showed a small residual pituitary tissue. However, this did show demyelination, con rming clinical suspicion at her initial presentation. Discussion In these case reports, we have demonstrated that screening for acromegaly with serum measurement of IGF-1 is not su cient to exclude GH excess: in each of the cases, serum IGF-1 was normal prior to initial surgery. Two of the patients were taking the oral contraceptive pill at this point, which may have served to lower circulating IGF The diagnosis of acromegaly is usually based on classic physical features associated with the disease: acral growth, coarsening of facial features, macroglossia, excessive perspiration, arthropathy and signs of generalized organomegaly, as well as impaired glucose homeostasis. Con rmation of diagnosis rests on the nding of elevated IGF-1 and GH levels, as well as nonsuppression of plasma GH during oral glucose tolerance test (OGTT) Ourthreecasespresentedwith pituitary macroadenomas, but with no clinical or biochemical evidence of raised IGF-1levels until after their pituitary surgery. Importantly, in two of the three cases, the patient was taking the oral contraceptive pill at the time of initial assessment. Silent somatotroph pituitary tumours are de ned as GH-secreting tumours with no clinical stigmata of GH excess Random GH and IGF-1 values in these patients varied from mildly elevated to normal. Several explanations have been suggested for the lack of clinical signs of hormone excess, but because of very limited data, the answer to this question is still unclear.

4 92 Kalavalapalli et al. At least two factors could be attributed to a falsely reassuring IGF-1 value, one being the e ect of the oral contraceptive pill or hormone replacement treatment 11,18,19 in underestimating the actual value as may well be the case in two of the patients described here. The second more di cult issue is the lack of true age- and gender-matched reference ranges for IGF-1 and the variability of performance between assay systems. 20 However, all IGF-1 assays performed on these patients used the same assay platform. An important contribution recently is the work of Brabant et al., 21 which established age- and sex-speci c reference values for the Nichols Advantage immunoassay system, with the assay calibrated against the World Health Organisation International Reference Reagent 87/518. The measurement of IGF-1 is widely used in the management of acromegaly for both diagnosis and follow-up Elevated circulating GH increases the concentration of GH-dependent peptides such as IGF-1, IGF-binding protein-3 (IGFBP-3) and acid labile subunit (ALS). Although certain metabolic functions including lipolysis are mediated directly by GH, many of the observed e ects of GH are the result of IGF-1 generation, 25, and a correlation between serum IGF-1 and clinical measures of disease activity is reported. 26 The relationship between serum GH and IGF-1 is linear below GH levels of approximately 40 mu/l, but at higher levels of GH secretion IGF-1 generation is maximally stimulated with no further increase in circulating IGF Present best practice is that both serum GH and IGF-1 are used to de ne treatment goals for acromegaly. A consensus statement has de ned biological cure as the return to normal of all attributes of disordered GH secretion, as evidenced by the suppression of serum GH below 1 mg/l after a 75 g oral glucose load and the presence of a normal age-matched serum IGF-1 value. 28 Numerous studies involving in a total of more than 2000 patients with acromegaly have demonstrated the bene t of lowering serum GH and the need for tight control. Crucially, the achievement of mean GH below 2.5 mg/l is associated with reduced mortality In these studies, the ratio of observed to expected deaths was increased fold in those patients with persistent disease activity (GH42.5 mg/l or 5 mu/l). Hence, measurement of serum GH remains integral to both initial diagnosis of acromegaly and assessment of treatment e ectiveness. Although serum IGF-1 is principally regulated by GH, other factors are believed to modulate the relationship between serum GH and IGF-1. In patients with acromegaly, discordant serum GH and IGF-1 results (either an elevated serum GH and normal IGF-1, or more commonly elevated serum IGF-1in the presence of acceptable GH levels) are seen in approximately one-third of patients. In a study designed to assess the diagnostic value of several di erent single measurements in comparison with the oral glucose tolerance in acromegaly management, in six out of 29 patients (21%) who had not been cured, circulating IGF-1 levels overlapped with those for non-acromegalic control subjects. 32 We propose that in two of the cases presented here, the fact that the patient was taking the oral contraceptive pill at the time of initial assessment may have resulted in the lowering of measured serum IGF-1. Our report emphasizes the need to be cautious when interpreting the values of IGF-1 in deciding on the need for further tests in evaluating pituitary tumours. Although it may seem simple and practical to rely on IGF-1 alone to exclude active acromegaly, our series demonstrates the complexity of management of this condition, particularly when it presents in an occult fashion. We suggest that, for optimal patient management, formal evaluation of GH status with oral glucose tolerance testing should ideally be performed in all individuals for whom pituitary surgery is planned. With such an approach, the entity of clinically silent somatotroph adenoma would not be missed. Acknowledgements We thank Dr Daniel DuPlessis, Consultant Neuropathologist, Cellular Pathology, Hope Hospital, Salford, UK, for invaluable help in preparing this manuscript. References 1 Giustina A, Barkan A, Casanueva F, et al. Criteria for cure of acromegaly: a consensus statement. J Clin Endocrinol Metab 2000; 85: Sakharova AA, Dimaraki EV, Chandler WF, Barkan AL. Clinically silent somatotropinomas may be biochemically active. J Clin Endocrinol Metab 2005; 90: Yamada S, Sano T, Stefaneanu L, et al. Endocrine and morphological study of a clinically silent somatotroph adenoma of the human pituitary. J Clin Endocrinol Metab 1993; 76: Horvath E, Kovacs K, Killinger DW. Silent corticotropic adenomas of the pituitary gland: a histologic, immunocytologic and ultrastructural study. Am J Pathol 1980; 98: Kovacs K, Lloyd R, Horvath E, et al. Silent somatotroph adenomas of the human pituitary. A morphologic study of three cases including immunocytochemistry, electron microscopy, in vitro examination, and in situ hybridization. Am J Pathol 1989; 134: Klibanski A, Zervas NT, Kovacs K, Ridgway EC. Clinically silent hypersecretion of growth hormone in patients with pituitary tumors. J Neurosurg 1987; 66: Stoffel-Wagner B, Springer W, Bidlingmaier F, Klingmuller D. A 8 Dimaraki EV, Jaffe CA, DeMott-Friberg R, Chandler WF, Barkan AL. Acromegaly with apparently normal GH secretion: implications for diagnosis and follow-up. J Clin Endocrinol Metab 2002; 87: Jaffe CA, Barkan AL. Acromegaly. Recognition and treatment. Drugs 1994; 47:

5 IGF-1 measurement is insufficient to exclude GH excess Robert F. Electron microscopy of human pituitary tumors. In: Tindall GT, Collins WF, eds. Clinical Management of Pituitary Disorders. New York: Raven, 1979; Helle SI, Omsjo IH, Cwyfan-Hughes SC, et al. Effects of oral and transdermal oestrogen replacement therapy on plasma levels of insulin-like growth factors and IGF binding proteins 1 and 3: a cross-over study. Clin Endocrinol 1996; 45: Stoffel-Wagner B, Springer W, Bidlingmaier F, Klingmuller D. A 13 Biochemical assessment and long-term monitoring in patients with acromegaly: statement from a joint consensus conference of The Growth Hormone Research Society and The Pituitary Society. J Clin Endocrinol Metab 2004; 89: Dimaraki EV, Jaffe CA, DeMott-Friberg R, Chandler WF, Barkan AL. Acromegaly with apparently normal GH secretion: implications for diagnosis and follow-up. J Clin Endocrinol Metab 2002; 87: Yamada S, Sano T, Stefaneanu L, et al. Endocrine and morphological study of a clinically silent somatotroph adenoma of the human pituitary. J Clin Endocrinol Metab 1993; 76: Klibanski A, Zervas NT, Kovacs K, Ridgway EC. Clinically silent hypersecretion of growth hormone in patients with pituitary tumors. J Neurosurg 1987; 66: Sakharova AA, Dimaraki EV, Chandler WF, Barkan AL. Clinically silent somatotropinomas may be biochemically active. J Clin Endocrinol Metab 2005; 90: Rosenfield RL, Devine N, Hunold JJ, Mauras N, Moshang Jr T, Root AW. Salutary effects of combining early very low-dose systemic estradiol with growth hormone therapy in girls with Turner syndrome. J Clin Endocrinol Metab 2005; 90: Heald A, Selby PL, White A, Gibson JM. Progestins abrogate estrogen-induced changes in the insulin-growth factor axis. Am J Obstet Gynecol 2000; 183: Pokrajac-Simeunovic A, Wark G, Wieringa GE, Trainer PJ. Variability in IGF-1 assay performance undermines its contribution to the management of GH disorders. British Endocrine Society Meeting, November 2004, Endocrine Abstracts 8; p Brabant G, von zur Muhlen A, Wuster C, et al. German KIMS Board. Serum insulin-like growth factor 1 reference values for an automated chemiluminescence immunoassay system: results from a multicenter study. Horm Res 2003; 60: Marzullo P, Di Somma C, Pratt KL, et al. Usefulness of different biochemical markers of the insulin-like growth factor (IGF) family in diagnosing growth hormone excess and deficiency in adults. J Clin Endocrinol Metab 2001; 86: Rieu M, Girard F, Bricaire H, Binoux M. The importance of insulinlike growth factor (somatomedin) measurements in the diagnosis and surveillance of acromegaly. J Clin Endocrinol Metab 1982; 55: Arosio M, Garrone S, Bruzzi P, Faglia G, Minuto F, Barreca A. Diagnostic value of the acid-labile subunit in acromegaly: evaluation in comparison with insulin-like growth factor (IGF) 1, and IGF-binding protein-1, -2, and -3 J. Clin Endocrinol Metab 2001; 86: Costa AC, Rossi A, Martinelli Jr CE, Machado HR, Moreira AC. Assessment of disease activity in treated acromegalic patients using a sensitive GH assay: should we achieve strict normal GH levels for a biochemical cure? J Clin Endocrinol Metab 2002; 87: Clemmons DR, VanWyk JJ, Ridgway EC, Kliman B, Kjellberg RN, Underwood LE. Evalation of acromegaly by radioimmunoassay of somatomedin-c. N Engl J Med 1979; 301: Barreca A, Ciccarelli E, Minuto F, Bruzzi P, Giordano G, Camanni F. Insulin-like growth factor 1 and daily growth hormone profile in the assessment of active acromegaly. Acta Endocrinol (Copenh) 1989; 120: Giustina A, Barkan A, Casanueva FF, et al. Criteria for cure of acromegaly: a consensus statement. J Clin Endocrinol Metab 2000; 85: Bates AS, Van t Hoff W, Jones JM, Clayton RN. An audit of outcome of treatment in acromegaly. Q J Med 1993; 86: Rajasoorya C, Holdaway IM, Wrightson P, Scott DJ, Ibbertson HK. Determinants of clinical outcome and survival in acromegaly. Clin Endocrinol (Oxf) 1994; 41: Orme SM, McNally RJQ, Cartwright RA, Belchetz PE. Mortality and cancer incidence in acromegaly: a retrospective cohort study. J Clin Endocrinol Metab 1998; 83: Stoffel-Wagner B, Springer W, Bidlingmaier F, Klingmüller D. A Accepted for publication 2 September 2006