Endocrine Abstracts

Introduction: Evaluation and management of thirst and polyuric syndromes can be challenging in endocrine practice.

Case report: A 24-year old lady presented with weight loss, thirst, polyuria, vomiting and abdominal pain. She had acromegaly treated by transsphenoidal surgery 5 years ago. Medications included hydrocortisone, thyroxine (T4), the oral contraceptive pill as well as bromocriptine for postoperative acromegaly. Examination revealed postural hypotension, bilateral optic atrophy and mild periumbilical tenderness. Investigations showed normal sodium and potassium, corrected calcium 3.01 mmol/l (reference 2.15-2.55), normal insulin like growth factor (IGF1), glucose 3.2 mmol/l, parathormone less than 0.08 pmol/l, normal water deprivation test, free thyroxine 111pmol/l (reference 10.3-19.4) and thyroid stimulating hormone (TSH) less than 0.03mu/l (reference 0.2-6.0). Hypercalcemia persisted after intravenous saline and hydrocortisone. TSH receptor antibody (TRAB) was positive and technetium thyroid uptake scan (after stopping T4 for 7 days) showed diffuse increased uptake, confirming Graves' disease. Hypercalcemia was corrected by propranolol and carbimazole.

Discussion: Total serum calcium is elevated in 27% cases of thyrotoxicosis, levels usually being less than 2.7 mmol/l. Other possible cases of hypercalcemia were glucocorticoid deficiency, dehydration, multiple endocrine neoplasia and acromegaly. Cranial diabetes insipidus was excluded by water deprivation test. The association of acromegaly and Grave's disease is rare. In a series of 80 patients with acromegaly, none had Graves' disease. Thyroid uptake scan and TRAB helped in confirming the diagnosis.