Objective: To compare basal and stimulated prolactin levels between patients with rheumatoid arthritis and healthy controls, and to assess the effects of antirheumatic treatment on prolactin concentrations.
Methods: Serum prolactin was assessed under basal conditions and during an insulin tolerance test (ITT) in 20 patients with recently diagnosed active rheumatoid arthritis and 20 age and sex matched controls. The patients were reassessed after two weeks' treatment with naproxen and after six months' additional treatment with either sulfasalazine or methotrexate. Disease activity was assessed by the disease activity score (DAS).
Results: Basal levels of prolactin were not significantly different between patients with rheumatoid arthritis and controls. Prolactin responses to hypoglycaemia were less in untreated rheumatoid patients than in controls. DAS scores correlated negatively with the area under the curve (AUC) for prolactin concentrations during the ITT. Treatment with naproxen for two weeks did not influence either basal or stimulated prolactin levels. After six months of antirheumatic treatment, prolactin responses to hypoglycaemia increased significantly to levels observed in controls. At the same time point, DAS had improved considerably. The improvement correlated with the increase in AUC of prolactin during the ITT (r = 0.48; p = 0.05).
Conclusions: Patients with active rheumatoid arthritis have a decreased prolactin response to hypoglycaemia induced stress. The response recovers following treatment with antirheumatic drugs.