Definition of Androgens:
- Androgens are male sex hormones responsible for developing and maintaining male characteristics. The primary endogenous androgen is testosterone.
Physiological Roles:
- Produced mainly by Leydig cells in the testes and, to a lesser extent, by the adrenal cortex.
- Regulate development of male secondary sexual characteristics, spermatogenesis, and libido.
- Exhibit anabolic effects: Promote protein synthesis, increase muscle mass, and stimulate erythropoiesis.
Physiology of Androgens:
- Major Androgens: Testosterone, Dihydrotestosterone (DHT, more potent), and Androstenedione.
- Regulation: Controlled by the hypothalamic-pituitary-gonadal (HPG) axis:
- Hypothalamus releases GnRH → Stimulates anterior pituitary to release LH → LH stimulates Leydig cells to produce testosterone.
Pharmacological Actions:
-
Androgenic Actions:
- Development and maintenance of male secondary sexual characteristics (facial hair, deep voice, etc.).
- Growth of male reproductive organs.
-
Mechanism of Action:
- Androgens bind to androgen receptors in target tissues, regulating gene expression and promoting male characteristics.
Pharmacological Agents:
- Testosterone: Natural androgen used for hypogonadism, delayed puberty, and breast cancer.
- Synthetic Androgen: Methyltestosterone, Fluoxymesterone—enhance androgenic effects and improve pharmacokinetics.
Clinical Uses of Androgens:
- Hypogonadism: Replacement therapy to restore testosterone levels.
- Delayed Puberty: Induction of puberty in adolescent males.
- Anemia: Stimulates erythropoiesis.
- Breast Cancer: Inhibits estrogen-dependent tumor growth.
Side Effects:
- Androgenic Effects: Acne, hair loss (male pattern baldness), and increased body hair.
- Estrogenic Effects: Gynecomastia due to aromatization of testosterone to estradiol.
- Other Risks: Liver toxicity (especially with oral forms), cardiovascular risks, mood swings, and infertility due to suppression of the HPG axis.
Thank you for reading from Firsthope's notes, don't forget to check YouTube videos!