Endocrine Abstracts

Giant prolactinomas are rare tumours, accounting for only 2–3% of all prolactin (PRL)-secreting tumours which can pose therapeutic challenges. It has a higher preponderance in men with a male to female ratio of about 9:1. A 70year old gentleman initially presented to the ophthalmology department with blurred and reduced colour vision. He denied any headache, galactorrhoea or gynaecomastia however he noticed reduced libido and difficulties with erections. His past medical history included hypertension, Type 2 Diabetes and renal stones. He reported no family history of endocrine disease or tumours. On examination, his weight was 92 kg, with a BMI of 31.A mild temporal left visual field defect was noted with normal eye movements. In view of the visual defect he had a brain MRI which demonstrated a large mass centred on the body of the sphenoid extending laterally into both cavernous sinuses the sphenoid wings and roof of the orbits with extension into the ethmoid air cells and left frontal air cells. The mass elevated the chiasm, floor of the third ventricle and anterior frontal lobes. He was subsequently referred to the pituitary service and initial biochemistry showed a random cortisol of 237 nmol/l, FSH 2.0 iu/l, LH 1.1 iu/l, TSH 1.42 mu/l (0.34–5.6), T4 8.5 mu/l (7.7–15), IGF-1 17.4 nmol/ (5.3–29), ACTH 23 ng/l (0–46), Testosterone 2.1 nmol/l (10.0–27.6), prolactin (post dilution) : 411, 237 mu/l (55–276), Renal, calcium and liver function profiles were normal. In liaison with neurosurgery he was commenced on cabergoline at a dose of 500 micrograms once weekly with views to increase to 500micrograms twice weekly as tolerated. He was also started on hydrocortisone given the indeterminate cortisol level and a short synacthen test was arranged. He was also started on levothyroxine 50 micrograms once daily for secondary hypothyroidism. He responded very well to medical therapy and his prolactin levels dramatically improving to 6911 mu/l.An interval pituitary MRI at 6 weeks showed modest reduction in the bulk of the macroprolactinoma with resolution of chiasmal compression. His subsequent prolactin levels were suppressed to latest of 97 mU/l and serial MRI scans showed progressive shrinkage of the giant tumour.

Conclusion

Dopamine agonists remain the first line treatment for giant macroprolactinoma in tumour size reduction and normalization of prolactin levels. Neurosurgical interventions are associated with high morbidity and mortality and best reserved when medical therapy is ineffective or not tolerated. Patients should be managed in Tertiary Centres within an MDT setting.