3β,5a-Tetrahydronorethisterone

3β,5a-Tetrahydronorethisterone, also known as tibolone, is a synthetic hormone used primarily in hormone replacement therapy (HRT) for postmenopausal women. It is a progestin, estrogen, and androgen agonist, which means it acts as a substitute for the naturally occurring hormones in the body. Tibolone is used to alleviate symptoms associated with menopause, such as hot flashes, night sweats, and vaginal dryness. It also helps to prevent osteoporosis by increasing bone density. Additionally, tibolone has been shown to have a positive effect on mood and cognitive function, making it an effective treatment for depression and anxiety in postmenopausal women. Chemically, tibolone is a derivative of norethisterone, a commonly used progestin in oral contraceptives. It is metabolized in the liver to form three active metabolites: 3α-hydroxytibolone, 3β-hydroxytibolone, and Δ4-isomer. These metabolites have varying degrees of activity on different hormone receptors in the body. Tibolone is generally well-tolerated, but like all medications, it may cause side effects such as breast tenderness, vaginal bleeding, and headaches. It is contraindicated in women with a history of breast cancer or liver disease, and should be used with caution in women with a history of blood clots or stroke.