Effects of Estrogen In Vivo and In Vitro on Spontaneous Interleukin-1 Release by Monocytes From Postmenopausal Women

Estrogen (E) inhibits bone resorption, but the mechanism of this effect is unknown. Interleukin-1 (IL-1) stimulates bone resorption in vitro and may be produced in bone by mononuclear phagocytes. Recently, the spontaneous release of IL-1 from peripheral monocytes was found to reflect bone formation in a subset of patients with idiopathic osteoporosis. We suspected that the action of E on bone is mediated indirectly by its effect on monocyte IL-1 activity. Eleven normal postmenopausal women taking no medications were given conjugated E (0.625 mg daily) for 3–9 weeks. Supernatants from cultured peripheral monocytes were analyzed for IL-1 production by stimulation of a cloned murine helper T-cell line. IL-1 release was expressed as a percentage of maximum release corrected for monocyte number. IL-1 release before E treatment was 11.0 ± 0.2% (±se), it was 7.8 ±1.6% after E treatment (P = NS). IL-1 release fell in each of the three women with the highest initial values (46% to 5%, 25% to 17%, and 18% to 12%). ...