Forty two year Mrs SJ, community support worker with a background history of hypothyroidism was referred by her GP with excessive tiredness and weight gain. She had been attending her surgery for few months with somatic symptoms and her GP had noticed significant change in facial characteristics and large hands. She complained of increase in her feet size from a size 6 to a 9. No disturbance of vision was reported.
She was noted to have hyperglycaemia and oral glucose tolerance test confirmed abnormal growth hormone levels. IGF1 was 128 nmol/l and GH levels were >40 μg/l at 0 min and 37.3 μg/l at 120 min. Prolactin level was elevated at 1800 mIU/l. Her synacthen and thyroid function tests were normal. An MRI scan demonstrated a predominantly intrasellar pituitary macroadenoma with no optic chiasm compression.
A week following the biochemical diagnosis of acromegaly she presented with headache, vomiting and fatigue for 2 days. We suspected pituitary apoplexy, however pituitary CT did not show any change in size of the pituitary adenoma nor did it demonstrate any sign of haemorrhage. A synacthen test was again normal. Her symptoms resolved spontaneously after 1 day. She was started on cabergoline 0.5 mg twice weekly and discharged. Following 4 weeks of treatment her prolactin had normalised but her IGF1 remained elevated (134 nmol/l).
She then presented with sudden onset polyuria and polydipsia and was admitted for a water deprivation test that confirmed the diagnosis of cranial diabetes inspidus. Her osmotic symptoms resolved with DDAVP 10 mg twice daily.
A subsequent MRI again showed a pituitary tumour measuring 2×1.5 cm as before but now with a concave superior border indicating shrinkage of tumour. The posterior pituitary bright spot had also disappeared.
The diagnosis here is pituitary adenoma producing GH which has undergone structural change, most likely as a result of haemorrhage or infarction, leading to the development of diabetes insipidus.