Endocrine Abstracts

Introduction: Cystic prolactinomas were historically considered resistant to dopamine agonists. However, recent case series including one by Faje et al. have highlighted their potential efficacy. We conducted an audit of cystic prolactinomas in Beaumont Hospital to assess this further.

Methods: Cystic prolactinomas were defined as a macroadenoma with a cystic component exceeding 50% of the adenoma volume and a prolactin of at least 2,000mIU/l. Data was extracted from patient’s medical records fulfilling this criterion.

Results: Fourteen patients with predominantly cystic prolactinomas were identified. Median age at presentation was 26 years (IQR 18.5-48.75), with an equal sex distribution. At diagnosis, 86% (n = 12) of patients had gonadotropin deficiency, while visual field (VF) defects were observed in 29% (n = 4). All patients were initially medically treated; the median cabergoline dose was 1 mg (IQR 0.5-3.75) per week. Gonadotropin deficiency and VF defects resolved in 71% (n = 10) and 75% (n = 3) of patients, respectively, with medical therapy. Prolactin normalised in 71% of patients (n = 10) after 4 months (IQR 4-12.5) on medical therapy. Prolactin declined from 9,831mIU/l initially (IQR 3,910-36,056) to 207mIU/l (IQR 93-743) after 35 months of follow up (IQR 25-69). Tumour shrinkage occurred in 79% (n = 12) of patients; the maximal adenoma diameter reduced from 17.5 (IQR 15-24.25) mm to 8mm (IQR 15-24.25), while the cystic component reduced from 13.5 (IQR 9.5-19.25) to 6mm (IQR 15-24.25) at last follow up. Four cystic prolactinomas involuted completely. Despite these responses, two patients underwent transsphenoidal surgery, one for a persistent VF defect while another had no biochemical or anti-tumour response to cabergoline.

Conclusion: Cabergoline therapy led to a rapid normalisation of prolactin levels and significant tumour shrinkage in over 70% of patients with cystic prolactinomas, including those with larger tumours and visual field defects. These findings strongly support the use of cabergoline as the first-line treatment for predominantly cystic prolactinomas.