Most autoimmune diseases are more prevalent in women than in men.  Sex hormons have an important role in the sex bias. Estrogens potentially stimulate autoimmunity and androgens play a protective role.

In sjogren’s syndrome, systemic lupus erythematosus (SLE), autoimmune thyroid disease and scleroderma show 7:1 – 10;1, and Rheumatoid arthritis, multiple sclerosis (MS) and myasthenia gravis show 2:1 – 3:1 (Women: Men), Surprisingly.

Women generally have stronger humoral and cellular immune responses than men. The sex hormones may alter response to environmental factors, such as microbial exposure and diet.

Generally, estrogens, in particular 17-β estradiol (E2) and prolactin, enhance at least    humoral immunity, on the other hand, testosterone and progesterone play as natural  immunosuppressants.  The E2 acts as anti-inflammatory, which reduces production of inflammatory cytokines as TNF, IL-1b, and IL-6. Prolactin increases antibody production and triggers pro-inflammatory cytokine production.

Pregnancy increases estrogen and progesterone at the highest levels.  These change enhanced severity of SLE which is T helper type 2 response dominant, by higher production of pathogenic autoimmune diseases while showing protective effect in T helper type 1 dominant autoimmune disease such as Rheumatoid Arthritis (RA) and MS.

Gut microbiota affects innate and adaptive immune responses. The sex-bias were reveled in animal studies. Non-Obese Diabetic spontaneous model of type I diabetes showed a strong female bias, interestingly gem-free female mice had similar disease rates with specific pathogen free male mice. This indicated that microbiota metabolism may be affected by sex-hormones.