Polymyalgia rheumatica (PMR) usually exhibits a good clinical response to glucocorticoid (GC) treatment, but early clinical symptoms may create some difficulties in the differential diagnosis with elderly onset rheumatoid arthritis (EORA), particularly in patients complaining of shoulder and pelvic girdle involvement at onset (PMR-like clinical onset) (EORA/PMR). Since neuroendocrine mechanisms seem to play a pathogenetic role in these clinical conditions, the aim of this study was to evaluate hormone and cytokine responsiveness to GC treatment in these patients. Cortisol (CO), dehydroepiandrosterone sulphate (DHEAS), 17-OH-progesterone (PRG), interleukin-1 receptor antagonist (IL-1Ra), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha) were evaluated at base line, and 1 month after GC treatment (prednisone 10 mg/day), in 14 PMR, 11 EORA/PMR, and 13 EORA patients (mean age 73 +/- 5 years, +/- SD, mean disease duration 3 +/- 2 months, +/- SD). No patient was taking GCs or immunosuppressive agents at base line. Following GC treatment, CO, DHEAS, and PRG decreased significantly in both PMR and EORA/PMR patients (P < 0.05), but not in EORA patients. On the contrary, IL-1Ra was significantly increased in both PMR and EORA/PMR patients (P < 0.05). IL-6 and TNF-alpha serum levels were significantly decreased in all groups of patients (P < 0.05). In conclusion, PMR and EORA/PMR seem to exhibit similar hormonal variations after GC administration, when compared to EORA patients. These differences suggest a deficient function of the hypothalamic-pituitary-adrenal (HPA) axis in PMR and EORA/PMR patients, with a related higher responsiveness to GC treatment. Interestingly, in PMR and EORA/PMR patients, GC treatment was found to downregulate PRG serum levels.