Endocrine Abstracts

Objective: Our objective was to examine recurrence of hyperprolactinaemia following discontinuation of dopamine agonist (DA) therapy in patients with macroprolactinoma who have had treatment for 3–15 years.

Methods: We identified retrospectively adult patients (n=15) attending OCDEM (Churchill Hospital, Oxford, UK) with a confirmed diagnosis of macroprolactinoma (established during the last 25 years), who had been treated with DA therapy for at least 3 years and had had a trial off DA therapy. None had any alternative treatment modalities and none were pregnant. Data collected included: age at diagnosis; sex; initial tumour dimensions and shrinkage with therapy; length of DA therapy; prolactin levels at baseline, during DA therapy and at recurrence (defined by prolactin higher than 375 mU/l (men) and 620 mU/l (women)); and time to recurrence.

Results: Fourteen patients (93%) had a recurrence of hyperprolactinaemia, 9 within 6 months and 13 within 1 year of discontinuing DA therapy. Mean time to recurrence was 8.8 months (S.D. 8.7). Mean time on DA therapy was 7.5 years (S.D. 3.4). All 15 patients achieved suppression of prolactin levels to normal during DA therapy. Mean initial tumour diameter was 2.0 cm (S.D. 0.6). The vast majority of patients (n=14) had tumour shrinkage with DA therapy (in nine patients down to a thin rim). In the 14 patients who recurred, mean prolactin level at baseline was 28 246 mU/l (S.D. 24 569). Prolactin levels during DA therapy and at recurrence were 144 mU/l (S.D. 105) and 2236 mU/l (range 411–12 847) respectively (P=0.05). Linear regression analyses revealed no predictors for recurrence.

Conclusions: In patients with macroprolactinoma who achieve normal prolactin levels and whose tumours shrink with DA therapy administered for 3–15 years, the vast majority (93%) experience a recurrence following discontinuation of DA therapy, most (64%) within 6 months. Our data argue against a trial off DA therapy in patients with macroprolactinoma.