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Androgens & Antiandrogens

Androgens & Antiandrogens. The testis has two major functions: 1. Spermatogenesis occurring within the seminiferous tubules 2. Production of androgenic hormones. Naturally occurring androgenic hormones are:

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Androgens & Antiandrogens

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  1. Androgens & Antiandrogens

  2. The testis has two major functions: 1. Spermatogenesis occurring within the seminiferous tubules 2. Production of androgenic hormones

  3. Naturally occurring androgenic hormones are: 1. Testosterone, the principal androgenic hormone produced by the Leydig cells of testis. 2. Dehydroepiandrosterone (DHEA) (Adrenal cortex produces DHEA) 3. Androstenedione The testes produce other hormones like 1) Small quantities of Estradiol 2) Inhibin and 3) Activin

  4. Testosterone synthesis From cholesterol DEDeh Cholesterol Pregnenolone Progesterone Hyd Testosterone Androstenedione Hydroxyprog. 5α-reductase 5α-dihydrotestosterone

  5. Androgens and anabolic steroids Testosterone is the natural androgen GnRH - ↓ LH; FSH - ↓ Testosterone; spermatogenesis

  6. Transport & MOA of androgens: SHBG 5α-reductase Testosterone 5α-dihydrotestosterone (sex organs) (skeletal muscles) cytosloic; nuclear receptors increase transcription of a specific protein androgen effects DHT is 10 times more potent than testosterone and mediates effects of testosterone on skin and sexual apparatus (prostate; seminal vesicle, epididymis…)

  7. Testosterone physiological & pharmacologicaleffects: • Virilizing=masculinizing effect 1° & 2° sexual characteristics • ↑ Spermatogenesis • ↑ Erythropoiesis • Anabolic or growth promoting effect (bone; skeletal muscles)

  8. Testosterone metabolism: Androsterone Hepatic → 17-ketosteroids Etiocholanolone • Clinical uses: • Testosterone deficiency Hypogonadism; impotency; ↓ libido; aging; infertility… • Anemia; leukemia; lymphoma • Endometriosis (Danazol is particularly used)

  9. Cont. Testosterone clinical uses, • Antiestrogenic effect Breast cancer • Anabolic effect Osteoporosis ** Use by athletes is an abuse

  10. Testosterone preparations: 1° use for androgen replacement: • Testosterone I.M; S.C • Testosterone propionate I.M, S.L • Testosterone cypionate I.M; depo I.M • Methyltestosterone O; S.L • Fluoxymestrone O 1° use for breast cancer: Testolactone (progesterone derivative and aromatase inhibitor) O

  11. Cont. testosterone preparations, 1° use for anabolism (osteoporosis): Androgen:anabolic ratio=1:2 or 1:3 (promote + ve anabolism and muscular growth but little effect on sex) • Ethylestrenol O • Stanozolol O • Oxandrolone O • Nandrolone decanoate I.M • Methandienone O

  12. Testosterone side effects: • Virilization (masculinization) Hirsutism; acne; menstrual disorders in ♀’s • Precocious puberty & hirsutism in children • Salt & water retention • Jaundice; gall bladder stones (methyltestosterone) • Enlargement of prostate • ? Liver cancer

  13. Antiandrogens • Estrogens: Diethylstilbesterol; mestranol... • Progestins: Cyproterone acetate • GnRH superagonists (Leuprolide acetate); GnRH antagonists (Ganirelix) Pro-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly • Flutamide; Bicalutamide and Nilutamide • 5α- reductase inhibitors: Finasteride • Ketoconazole • Spironolactone • Gossypol

  14. Antiandrogens clinical uses: • Ca prostate • Benign hyperplasia of the prostate (Finasteride) • Severe acne and hirsutism in ♀’s (Spironolactone; Cyproterone acetate) • Precocious puberty • ♂ antifertility agents (♂ contraceptive) (Gossypol) • ♂ baldness (Cyoctol=topical antiandrogen; Finasteride) • Antiandrogens side effects: ↓ libido; impotency; ↓ spermatogenesis; ↓ ejaculate

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