Physiological Roles of Androgens

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Physiological Roles of Androgens

• Maintain sex accessory and external genitalia
• Behavior
• Mating behavior and libido (males females)
• Aggression
• Spermatogenesis
• Sperm maturation (spermiogenesis)
• Cryptorchidism
• Disorganization of semin. tubules, germ cells
  degenerate, T secretion is reduced later

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Physiological Roles of Androgens

• Pre-pubertal Growth and Differentiation of Male
  Reproductive tract
• Epididymus, prostate, seminal vesicles, vas def
• External genitalia (penis, scrotum)
• Brain hypothalamus, POA, cortex , libido

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Physiological Roles of Androgens

• Pubertal and Post-pubertal effects
• Skeletal muscle and bone growth
• Male pattern hair and beard growth
• Vocal cords (larynx)
• Growth of accessory organs
• Prostate
• Seminal Vesicles

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Pulsitile Release of Testosterone
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Effect of Age on Testosterone Secretion
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Effect of Testosterone on Adult Male Rats

• Low dose (relative to endogenous)
• Little or no effect (because of endogenous
  androgens)
• High dose (relative)
• Increase prostate, seminal vesicle weight
• Decrease thymus weight
• Decrease adrenal weight

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Effect of Testosterone on Castrated Male Rats

• Maintainence dose
• Increased prostate
• Increased seminal vesicle weight
• Increased Levator ani muscle size

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Effect of Androgens on Adult Female Rats

• Low or High Dose (same doses given males)
• Increased body wt. (? muscle), food consumption,
  uterine wt., liver wt. ( liver enzymes)
• Decreased ovarian wt, estrus cycles, LH FSH,
  adrenal wt., thymus wt., vaginal keratinization.

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Effect of Antiandrogens

• Flutamide
• Androgen receptor antagonist
• (non-steroidal)
• No hormonal activity
• Does not inhibit LH or FSH secretion
• Does inhibit negative fdbk from T
• ? T levels rise over time until the flutamide
  effects are overcome

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Effect of Antiandrogens

• Cyproterone Acetate
• Two major activities
• Androgen Receptor Antagonist
• Inhibits LH FSH secretion (progestational
  activity)
• ? stops T production by testes
• Chemical castration
• Inhibits libido and 2? sex characteristics
• Sometimes used on sex offenders

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Male Contraception

• Testosterone Enanthate
• s.c./i.m. injection slow release
• Peripheral T conc. Maintained
• Libido and 2? sex characteristics also maintained
• LH, FSH and intratesticular T conc. not high
  enough to maintain spermatogenesis
• Disadvantages
• Long lag time 2-3 months before effective
• Injections

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