Androgens

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:

1. Androgenic Actions:

   • Development and maintenance of male secondary sexual characteristics (facial hair, deep voice, etc.).
   • Growth of male reproductive organs.

2. 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.

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