gestagen

Gestagen is a class of steroid hormones with progestational activity, most notably the natural hormone progesterone and its synthetic derivatives. In physiology and clinical medicine, gestagens regulate the female reproductive system and support pregnancy by acting on progesterone receptors. The term is used in endocrinology and pharmacology to describe substances with gestational activity, encompassing both natural progesterone and synthetic progestogens, often referred to as progestins in modern usage.

Gestagens bind to progesterone receptors (PR-A and PR-B) in target tissues such as the endometrium and cervix. In the endometrium they promote secretory transformation and reduce proliferative activity. They suppress ovulation by negative feedback on the hypothalamic-pituitary axis, lowering GnRH and circulating LH and FSH. They also modify cervical mucus and uterine/tubal motility to reduce the likelihood of fertilization and implantation.

Clinically, gestagens are used in contraception and hormone replacement therapy. As part of combined estrogen–progestin regimens, the progestin component provides gestagen activity to prevent ovulation and alter the endometrium. Progestogens are also used alone (progestin-only pills) or for luteal-phase support in assisted reproduction. In hormone replacement therapy, gestagens prevent endometrial hyperplasia in women with a uterus receiving estrogen. They are employed to treat gynecological conditions such as endometriosis, abnormal uterine bleeding, and to protect the endometrium during estrogen therapy.

Although the terms evolve, progestin is the widely used pharmacological term for synthetic gestagens. The category also includes natural progesterone. Examples of gestagens include natural progesterone and synthetic progestogens such as levonorgestrel, norethindrone, desogestrel, gestodene, drospirenone, and medroxyprogesterone acetate.

Common side effects include mood changes, weight gain, breast tenderness, and headaches. Some progestogens carry an increased risk of thromboembolism, particularly in combination with estrogens, and different agents vary in androgenic or metabolic effects. As with all hormonal therapies, gestagens should be used under medical supervision, with consideration of pregnancy status, contraindications, and monitoring.