Endocrine Abstracts

Case history: A 39 year old lady was referred to the endocrinology clinic with difficulty conceiving, after screening bloods revealed an elevated prolactin (1816 miu/l)). There was no past medical history or family history of note and she took no regular medications. She denied headache, visual disturbance or galactorrhoea. Systemic examination was normal.

Investigations: Elevated prolactin was confirmed on a cannulated sample (1435 miu/l). Further analysis excluded macroprolactin. Her pituitary profile and basic bloods were otherwise unremarkable. MRI revealed a 6mm pituitary tumour, consistent with a microprolactinoma. Humphrey visual field testing demonstrated normal visual fields.

Treatment: Our patient was started on bromocriptine 1.25 mg bd, uptitrating to 2.5 mg bd after 2 weeks. Prolactin levels have improved, but she is yet to conceive.

Discussion: Microprolactinomas are common in the endocrinology clinic, and frequently seen in young female patients desirous of pregnancy. Dopamine agonists restore ovulation in up to 90% of such cases, but there remains considerable debate about drug choice and dose. Bromocriptine is usually favoured in these patients, given the extensive experience with this drug in early pregnancy. However, cabergoline appears to offer equivalent safety, along with a superior efficacy, dosing regimen and side effect profile. Serious consideration should be given to cabergoline as initial treatment in this population, particularly in older patients attempting pregnancy who would benefit from conceiving sooner rather than later.

Once pregnancy has been achieved, the approach is less controversial. Risk of tumour enlargement is only 2% with microprolactinomas, so there is widespread consensus that dopamine agonists should be withdrawn. Subsequent follow up should focus on clinical evaluation and visual field testing if indicated, as opposed to serial prolactin levels which do not correlate with tumour enlargement in pregnancy.