A steroidal antiandrogen (SAA) is an antiandrogen with a steroidal chemical structure. They are typically antagonists of the androgen receptor (AR) and act both by blocking the effects of androgens like testosterone and dihydrotestosterone (DHT) and by suppressing gonadal androgen production. SAAs lower concentrations of testosterone through simulation of the negative feedback inhibition of the hypothalamus. SAAs are used in the treatment of androgen-dependent conditions in men and women, and are also used in veterinary medicine for the same purpose. They are the converse of nonsteroidal antiandrogens (NSAAs), which are antiandrogens that are not steroids and are structurally unrelated to testosterone.
SAAs are used in clinical medicine for the following indications:
Prostate cancer in men
Benign prostatic hyperplasia in men
Androgen-dependent skin and hair conditions like acne, hirsutism, seborrhea, and pattern hair loss (androgenic alopecia) in women
Hyperandrogenism, such as due to polycystic ovary syndrome or congenital adrenal hyperplasia, in women
As a component of hormone therapy for transgender women
Precocious puberty in boys
Hypersexuality and paraphilias in men and sex offenders
Priapism in men
Unlike NSAAs, most SAAs show off-target hormonal activity such as progestogenic, glucocorticoid, or antimineralocorticoid activity, possess antigonadotropic effects, and are weak partial agonists of the AR with some capacity to activate the receptor. Due to their antigonadotropic effects, SAAs lower androgen levels in addition to directly blocking the actions of androgens at the AR; at sufficiently high dosages, they are able to lower circulating testosterone levels by up to 70 to 80% in men, to just above the castrate range. However, due to their other hormonal effects, suppression of estrogen levels alongside testosterone levels, and AR activation, SAAs have increased side effects and show lower efficacy in the treatment of prostate cancer relative to NSAAs.
Cyproterone acetate (Androcur): A combined AR antagonist and progestogen/antigonadotropin.
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Spirolactones are a class of functional group in organic chemistry featuring a cyclic ester attached spiro to another ring system. The name is also used to refer to a class of synthetic steroids, called steroid-17α-spirolactones, 17α-spirolactosteroids, or simply 17α-spirolactones, which feature their spirolactone group at the C17α position. They are antimineralocorticoids, or antagonists of the mineralocorticoid receptor (which is activated predominantly by the mineralocorticoid steroid hormone aldosterone), and have been employed clinically as potassium-sparing diuretics.
Osaterone acetate, sold under the brand name Ypozane, is a medication which is used in veterinary medicine in Europe in the treatment of enlarged prostate in dogs. It is given by mouth. Osaterone acetate is an antiandrogen, and hence is an antagonist of the androgen receptor, the biological target of androgens like testosterone and dihydrotestosterone. It is also a progestin, or a synthetic progestogen, and hence is an agonist of the progesterone receptor, the biological target of progestogens like progesterone.
Spirorenone (INN) (developmental code name ZK-35973) is a steroidal antimineralocorticoid of the spirolactone group that was never marketed. Spirorenone possesses 5–8 times the antimineralocorticoid activity of spironolactone in animal studies. The initial discovery of spirorenone was deemed a great success, as no compound with greater antimineralocorticoid activity had been developed since spironolactone in 1957.
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