Endocrine Abstracts

A 55 year old gentleman, previously fit and well, presented with an insidious onset of visual disturbance, tiredness and frontal headaches over 2 years, which had been worsening during the previous 3 months. A routine optician review revealed bi-temporal hemianopia and prompted endocrine referral. Apart from superior bi-temporal hemianopia, clinical examination was otherwise normal. Serum prolactin levels were grossly elevated at 544,800 mU/l with no macroprolactin. Despite the massive elevation of prolactin, there was no galactorrhoea. A short synacthen test was normal [447 nmol/l (0 min), 836 nmol/l (30 min)]. TSH was 1.86 mU/l with low normal free T4 (9.4 pmol/l) and normal free T3 (4.1 pmol/l). Rest of the pituitary function tests were normal except for low serum testosterone (5.0 nmol/l). MRI of pituitary showed a large expanding mass involving the sella/supra and para-sellar regions. There was encasement of the left cavernous sinus and anterior cerebral arteries and marked displacement of the frontal horns of the lateral ventricles. Patient was commenced on medical therapy with cabergoline, titrated to a dose of 1 mg/week with subjective improvement of visual symptoms. Serum prolactin levels fell steeply to 251,700 mU/l by 3 weeks and decreased further (92950 mU/l at 4 weeks and 27050 mU/l at 8 weeks). A follow-up MRI is awaited at 12 weeks.

The height of serum prolactin elevation in this case is the highest ever reported to our knowledge. Galactorrhoea is relatively rare in men with prolactinoma and was absent in our case, despite the massive elevation of prolactin. Interestingly, as the mass expanded more posteriorly, there was relative preservation of anterior pituitary functions except for hypogonadotrophic hypogonadism. The response to dopamine agonist treatment was dramatic and supports the view that they should be considered as first line management in these cases. It remains to be seen if the decrease in serum prolactin is matched by reduction in tumour size and if neurosurgical intervention would still be required.