Endocrine Abstracts

We present a 35-year-old male who was incidentally found to have a large macroadenoma when he presented with left sided weakness three months ago. He had no headaches or visual disturbances. His prolactin at presentation was >100 000 mU/l (86–324 mU/l). Magnetic resonance imaging confirmed an invasive macroadenoma. His Humphrey’s visual field tests were normal.

Rest of the endocrine profile revealed a normal T₄ of 14.3 (12–22 pmol/l), basal cortisol of 339 rising to 923 nmol/l at 60 min after synacthen. His testosterone and IGF 1 were low at 8.3 nmol/l (10–28 nmol/l) and 8.5 nmol/l (15–39.9 nmol/l) respectively with normal gonadotrophins of LH: 3.2 (2–9 U/l) and FSH: 4.8 U/l (2–12 U/l). Renal function is normal (urea: 3.1 mmol/l (2.5–7.5 mmol/l) and creatinine: 60 umol/l (62–106 umol/l).

He was started on cabergoline at a dose of 500 mcg twice a week for his macroprolactinoma. However, this has resulted in CSF rhinorrhoea (confirmed by positive tau protein) within four weeks of starting medical treatment. His prolactin levels dropped significantly to 23 277 mU/l within this time and expectedly his repeat MR scan showed significant shrinkage in tumour size.

Cabergoline was discontinued briefly and this improved the CSF leak. After few days, cabergoline was recommenced at a lower dose of 250 mcg twice weekly with close surveillance. His most recent prolactin was 50 585 mU/l and the CSF leak has settled.

CSF rhinorrhoea as a complication of treatment with dopamine agonists for macroprolactinomas has been described previously. However, the usual treatment advocated is neurosurgery with repair of CSF leak. In our patient we have managed to avoid surgery by carefully titrating the dose of cabergoline to avoid CSF leak.

This case highlights that conservative treatment with dose adjustment of cabergoline is safe and effective as long as good surveillance is executed to avoid significant CSF leak and thereby minimising the risk of meningitis.