Steroid sex hormones have a significant effect on different organ systems. As far as gingiva are concerned, they can influence the cellular proliferation, differentiation and growth of keratinocytes and fibroblasts. Estrogen is mainly responsible for alterations in blood vessels and progesterone stimulates the production of inflammatory mediators. In addition, some micro-organisms found in the human mouth synthesize enzymes needed for steroid synthesis and catabolism. In women, during puberty, ovulation and pregnancy, there is an increase in the production of sex steroid hormones which results in increased gingival inflammation, characterized by gingival enlargement, increased gingival bleeding and crevicular fluid flow and microbial changes.