Newer Dopaminergic Agents Cause Minimal Endocrine Effects in Idiopathic Parkinson’s Disease

OBJECTIVE: We studied the prevalence of endocrine dysfunction in subjects with idiopathic Parkinson’s disease (IPD) on newer dopaminergic agents (DA). DA are also used in endocrine hypersecretory states in small doses and we hypothesized that endocrine dysfunction was likely in IPD where DA were used in comparatively much higher dosage. PATIENTS AND METHODS: Twenty-five subjects with IPD, established on DA, were recruited to this cross-sectional study. We measured insulin-like growth factor-1, prolactin, luteinizing hormone, follicle stimulating hormone, thyroid function, oestradiol or testosterone and cortisol levels following a short synacthen test. RESULTS: We studied 18 males and 7 females, whose median age was 72 years, and whose median time from diagnosis, and duration of treatment was 27 months (interquartile range 17–45 and 13–39 months, respectively). (1) Endocrine tests were normal in 19 of 25 subjects at recruitment. Minor abnormalities reverted to normal on repeat testing in three of six with initial abnormalities; two had persistent abnormalities and the third subject could not be further investigated. Therefore, 22 of 24 (92%) with IPD on DA therapy had normal endocrine profiles. (2) The cortisol response to ACTH was normal in 24 of 25 subjects (96%). (3) Eleven subjects (44%) had isolated PRL suppression. There were no differences between the suppressed PRL and “normal” PRL groups. However, a higher number of them were on non-ergoline-derived DA (83% vs 31%; P < 0.05). CONCLUSIONS: We have demonstrated that newer non-ergoline DA therapy caused only minimal endocrine perturbations in subjects with IPD. Their clinical significance can only be speculative currently. The cortisol response to ACTH was normal in almost all but a significant minority had suppressed prolactin levels.