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Sex steroid hormones
Medical expert of the article
Last reviewed: 05.07.2025
Based on their biological action, as well as the sequence and number of carbon atoms (18, 19, 21) in their molecules, sex steroids are divided into three main groups.
- From 18 - estrogens (the main representatives are estradiol, estrone, estriol).
- From 19 - androgens (the main representative is testosterone).
- From 21 - gestagens (the main representative is progesterone).
In the female body, the most important sex steroids are formed in the ovaries and adrenal cortex, and during pregnancy - in the placenta. The main sex steroids of the male body (androgens) are synthesized in the testicles and, in small quantities, in the adrenal cortex.
All sex steroids and hormones of the adrenal cortex are derivatives of cholesterol. Steroids are lipophilic, which causes their low solubility in water, so 95% of steroid hormones in the blood are bound to specific transport proteins. With the help of transport proteins, hormones are transported to their target organs. Only free, non-protein-bound steroids have a biological effect. Steroid-binding globulin (SBG) specifically binds estradiol and androgens with high affinity, while corticosteroid-binding globulin binds progesterone and glucocorticosteroids. In addition to their transport function, hormone-binding proteins protect steroids from metabolic inactivation along the way from the secreting gland to the target organ.
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