Pharmacology · MU Sofia

67. Male sex hormones– drugs and clinical application. Anabolic drugs. Drugs for the treatment of erectile dysfunction.

Covers male sex hormones, mainly testosterone, and the synthetic androgen methyltestosterone, alongside PDE5 inhibitors for erectile dysfunction such as sildenafil, tadalafil and vardenafil. Sets out pharmacodynamics, a pharmacokinetics table comparing routes, half-lives and excretion, side effects, drug interactions with warfarin and nitrates, and therapeutic uses. Ends with recap questions on 5-alpha-reductase, Viagra's mechanism and oral testosterone's limited effectiveness.

Inside: 1 section · 4 labelled pictures · 1 table · 10 flashcards · 2 min

Topic 66 of 93 in the MU Sofia syllabus for Pharmacology (Medicine, Year 3). The free AceMed note covers it in 1 section, about 280 words (2 min of reading), with 10 flashcards.

In this note

  1. Male Sex Hormones

Male Sex Hormones

Male sex hormones, primarily testosterone, play key roles in the development and maintenance of male characteristics and reproductive functions.

Classification

  • Natural Androgen:
  • Testosterone
  • Synthetic Androgen:
  • Methyltestosterone
  • Drugs for Erectile Dysfunction (PDE5 Inhibitors):
  • Sildenafil (Viagra)
  • Tadalafil
  • Vardenafil

Pharmacodynamics

  • Testosterone / Androgens:
  • Develop male secondary sexual characteristics: facial/body hair, voice deepening, increased muscle mass
  • Stimulate growth and function of male reproductive organs: penis, testes, prostate
  • Maintain muscle mass, bone density, and male body fat distribution
  • Crucial for spermatogenesis
  • Regulate libido and overall sexual function
  • Prevent osteoporosis by maintaining bone health
  • PDE5 Inhibitors (e.g., Sildenafil):
  • Inhibit phosphodiesterase-5 (PDE5) in the corpus cavernosum
  • Prevent breakdown of cGMP, allowing smooth muscle relaxation
  • Enhances blood flow to the penis → helps erection

Pharmacokinetics

Side Effects

  • Testosterone:
  • Acne, oily skin
  • ↑ RBC count (polycythemia)
  • Gynecomastia
  • Edema (fluid retention)
  • Mood swings
  • Risk of liver damage, heart disease, prostate cancer, sleep apnea, and blood clots
  • Sildenafil (Viagra):
  • Headache, flushing
  • Indigestion, nasal congestion
  • Dizziness
  • Serious: vision loss, hearing loss, priapism, severe hypotension, heart attack, stroke

Drug Interactions

  • Testosterone:
  • ↑ bleeding risk with warfarin
  • Alters blood sugar control with insulin/oral antidiabetics
  • ↑ edema risk with corticosteroids
  • Potentiates hepatotoxic drug effects
  • Sildenafil (Viagra):
  • Dangerous hypotension with nitrates (e.g., nitroglycerin)
  • Caution with alpha-blockers (additive hypotension)

Therapeutic Uses

  • Testosterone:
  • Male hypogonadism
  • Delayed puberty in boys
  • Hormone therapy for transgender men
  • Treatment of certain breast cancers in women

Recap Questions

  1. 1. What is the role of 5-alpha-reductase in testosterone metabolism?
  2. 2. Which enzyme does Viagra inhibit, and what does this lead to?
  3. 3. Name two common side effects of testosterone therapy.
  4. 4. Why is oral testosterone less effective compared to IM or transdermal forms?
  5. 5. What is the main danger of combining Viagra with nitrates?

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