Endocrine Abstracts

A 19 year old university student who participated in athletics presented with secondary amenorrhoea. Examination revealed no features of endocrine disease. A pituitary profile showed normal serum thyroid function and prolactin, but undetectable LH, FSH, and oestradiol. Random serum GH level was detectable (9 milli units per litre), but IGF1 level was low, 72 (190-530 micrograms per litre). An OGTT demonstrated a paradoxical rise in her GH levels (3.5, 2.2, 38, 33, 20; mean GH 19.3 milli units per litre). An MRI revealed a 4.5 millimetre right-sided pituitary microadenoma. There were no clinical signs of acromegaly but despite this, a diagnosis of acromegaly was made and the patient underwent a transphenoidal hypophysectomy. Histology revealed normal pituitary tissue. She was then referred to us for a second opinion. Her amenorrhoea had resolved. Direct questioning revealed that she had lost 12 kilograms prior to initial presentation through competitive running and binge eating and vomiting. Her BMI at the time of initial diagnosis was 17.6. Examination was normal. Her BMI had risen to 20. A repeat pituitary profile revealed normal LH, FSH and oestradiol. Her GH was still detectable, 5.9 milli units per litre, but IGF1 was still low 13.6 (15-64 nanomoles per litre). An OGTT showed lack of suppression of GH levels (7.2, 3.1, 1.0, 9.7, 13.7; mean GH 7 milli units per litre). A repeat MRI still showed a 4.5 millimetre right-sided adenoma. This patient had dysfunction of her GH axis secondary to anorexia nervosa and excessive exercising. This case highlights that dynamic endocrine tests can be misleading in patients with eating disorders and the importance of using endocrine results to confirm clinical diagnoses, rather than making diagnoses on the numbers alone.