Hormones, pregnancy, and rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disorder that, like most autoimmune diseases, is more common in women than in men. A significant body of evidence implicates gender-specific factors in facilitating the development of RA. Pregnancy has an ameliorating effect on disease activity, while the disease tends to flare in the postpartum period. Estrogen-containing oral contraceptives can modify the disease course or onset, hinting at a role for this hormone in disease pathogenesis. Breast-feeding appears to increase the risk of RA, possibly through the actions of the lactation hormone prolactin. Nonhormonal factors associated with pregnancy may also be important in women with RA, especially the degree of maternal-fetal human leukocyte antigen (HLA) incompatibility. This article reviews data from human clinical and epidemiologic investigations as well as experimental findings in animal models of chronic arthritis. Possible mechanisms by which gender-specific factors modulate immune function are also discussed.