SAT-467 Gigantism Caused by Growth Hormone-Secreting Pituitary Macroadenoma: A Case Report

Abstract

Abstract Background Gigantism is a rare condition where excessive secretion of growth hormone (GH) occurs before fusion of the epiphyseal growth plates. Clinical Case A 23-year-old Sri Lankan male presented to the Endocrine clinic with extreme tall stature, and was diagnosed to have pituitary gigantism. He had been the tallest in his class since 5 years old. Pubertal development from 12 years of age was normal. There was no history of headache, visual disturbance, galactorrhea or any hypogonadal symptoms. Family history was non-contributory. On examination, there were clinical features of frontal bossing, prognathism, and prominence of supra-orbital ridge. He was 196cm in height (calculated midparental height of 171cm) and at Tanner stage 5. Initial medical treatment was started with cabergoline for 1 year, before decision for surgical treatment was sought in Singapore. Initial laboratory investigations revealed an elevated serum insulin-like growth factor-1 (IGF-1) value of 577ng/mL (RR: 116-358ng/mL), and failure of GH suppression during an oral glucose tolerance test, with GH nadir of 3.99 ng/mL (RR: <1 to 13.4ng/mL, no gender nor age-specific cut offs were provided). Prolactin was 132 mIU/L (RR 77-274mIU/L) and total testosterone was 11 nmol/L (RR 5-30nmol/L). Basal cortisol, thyroid function test, and calcium levels were normal. Pituitary magnetic resonance imaging showed a hypo-enhancing focus in the left lateral aspect of the pituitary gland with extension into the sphenoid sinus, measuring 12mm in size at largest diameter, which was suspicious for a pituitary adenoma. He subsequently underwent transphenoidal surgery, and there were no immediate complications post operatively. During a follow up visit 3 months after surgery, laboratory investigations showed normalization of GH (0.33 ng/mL), IGF-1 (212 ng/mL) levels, and normal GH suppression during OGTT. Conclusion Pituitary gigantism occurs during the pre-pubertal period of active linear growth, where elevated GH and IGF-1 levels result in extreme growth acceleration and tall stature (1). The treatment of choice for well-circumscribed pituitary adenomas is transphenoidal surgery, which may be curative (2). References 1.Colao A, Pivonello R, Di Somma C, TauchmanovàL, Savastano S, Lombardi G. Growth hormone excess with onset in adolescence: clinical appearance and long-term treatment outcome. Clin Endocrinol (Oxf). 2007;66(5):714. Epub 2007 Mar 27. 2. Nomikos P, Buchfelder M, Fahlbusch R . The outcome of surgery in 668 patients with acromegaly using current criteria of biochemical cure . Eur J Endocrinol. 2005;152(3):379.