Newer Dopaminergic Agents for Idiopathic Parkinson's Disease Have Minimal Endocrine Effects

For decades, dopaminergic agents have been the mainstay treatment for idiopathic Parkinson’s disease (IPD). But because the drugs are administered in lower doses to treat endocrine hypersecretory diseases, scientists have wondered whether they might cause endocrine dysfunction.

For their cross-sectional study published in Clinical Medicine Insights: Endocrinology and Diabetes, investigators in Great Britain recruited 25 IPD patients who had taken a variety of the newer, non-ergoline-derived dopaminergic agents — including pramiprexole, ropinirole, rotigotine, selegeline, entacapone, co-beneldopa, and co-careldopa — for a minimum of 6 months, with median treatment duration of 27 months.

After excluding patients with diabetes, bronchial asthma, stroke, pituitary disease, thyroid disorders, and malignant disease — in addition to those receiving beta blockers, hormone replacement, and neuroleptic therapy — the study group was comprised of 18 males and 7 females with a median age of 72.

During the study, the researchers measured insulin-like growth factor-1, prolactin, luteinizing hormone, follicle stimulating hormone (FSH), thyroid function, estradiol or testosterone (T), and cortisol levels following a short synacthen test.

At the conclusion of the study, the authors found:

• Twenty-three of the 25 (92%) patients displayed endocrine function within normal ranges at recruitment and repeat testing.
• Twenty-four (96%) patients had a normal cortisol response to the synacthen test.
• Eleven (44%) patients had suppressed prolactin levels, which the researchers expected to be revealed during the use of high-dose dopaminergic agents.

There appeared to be no significant differences in duration of dopaminergic treatment or time from IPD diagnosis between patients with suppressed prolactin levels and those with normal prolactin levels.

Although they recognized the limits of the study’s small sample size, the researchers concluded the newer non-ergoline-derived dopaminergic agents appeared to cause only minimal endocrine effects when used to treat IPD.