Endocrine Abstracts

A 37 year old male presented with visual problems in June 2006.

He gave a history of double vision for 18 months and denied headaches.

On examination his Glasgow coma score was 15/15, pupils were equal and reactive to light. Visual acuity; right eye - 6/6, left eye- 6/60. Visual field testing showed a temporal field defect in the right eye and poor vision in the left eye.

MRI brain scan showed a very large, fairly homogeneous, enhancing mass centred on the clivus, displacing the brain stem posteriorly. A multi lobulated, part cystic superior component, extended into the supra sella cistern, obliterating the optic chiasm. The mass extended anteriorly into the optic canals and the retro orbital space on the left compressing the intra cranial and intra orbital components of the optic nerves.

Endocrine testing- Prolactin- 1270000 mU/l LH, 2.7 U/L, FSH 3.9 U/L, Testosterone 15.8 nmol/l, IGF-1 18.2 nmol/l (14.2–36.9) TSH 2.6 mU/L, FT4 10 pmol/l Short synacthen test- normal cortisol response Tumour biopsy was inconclusive.

The diagnosis of Macroprolactinoma was made and treatment was commenced with cabergoline. Rapid response was noted on MRI pituitary and decrease in prolactin levels over subsequent four months-1270000 mU/l, 9039, 1691, 358 & 257 mU/L.

Patient was warned of potential CSF leak during treatment. The normal gonadotrophin levels were a surprising finding, given the high prolactin level.

The term ‘giant prolactinoma’ can be used for tumours larger than 4 cm in diameter and with massive extrasellar extension. Cabergoline, a long-acting dopamine agonist, safe and well tolerated, is effective in normalizing prolactin levels and inducing tumour shrinkage in giant macroprolactinoma.