Testosterone

ExRx.net > Exercise Information > Menu > Hormones

Testosterone

  • Testosterone is an anabolic/androgenic hormone.
  • Naturally produced in both men and women.
    • Men: Testis and Adrenal Cortex
    • Women: Adrenal Cortex
    • Men normally have 10 times the resting serum testosterone concentration of women (Kraemer et al. 1991)
  • Function
    • Increased body growth
    • Increased deposition of bone salts
    • Adult levels stimulate epiphyseal plate closure
    • Postnatal increases contributes to larger fibers from induction of muscle protein accretion
  • SHBG Protein Binding
    • More binding
      • less free testosterone
  • Bioavailable Testosterone
    • Increased by diets high in fat and protein
    • Decreased in vegan diets (as is IGF-I)
    • Decreased in diets high in carbs
    • Decreased if soy protein is substituted for meat protein
      • Habito RC, Montalto J, Leslie E, Ball MJ (2000). Effects of replacing meat with soyabean in the diet on sex hormone concentrations in healthy adult males. Br J Nutr. 84(4):557-63.
    • Percentage free is 1.6 to 2.9 percent

Male Free Testosterone Level
Age 20-40 40-50 50-60 70+
ng/ml 400-1080 350-890 250-750 250-650

Testosterone Production

  • Pituitary
    • secretes Luteinizing Hormone (LH)
    • affects Testes
  • Cholesterol
    • -> Pregnenolone
      • -> Progesterone
        • -> Aldosterone (mineral balance)
        • -> Cortisol (stress)
        • -> Androstenedione
          • See Androstenedione's conversion below
      • -> DHEA
        • -> Androstenedione
          • -> Estrone
          • <-> Testosterone
            • Free (active)
              • decreases with SHBG (see below)
            • Bound (inactive)
              • Sex Hormone Binding Globulin (SHBG)
                • Increases with age
                • Increases with high estrogen
                  • brought about by blood sugar imbalance
            • -> Dihydrotestoterone (DHT)
            • -> Estradiol
              • About one percent of testosterone is converted to estrogen

Defects Resulting in Low Testosterone Symptoms

  • Elevated Stress
    • increases Cortisol
      • suppresses Pituitary function
      • 'Pregnenolone Steal' during chronic stress
        • body favors Cortisol production
          • over sex hormone production
          • for survival
      • increased blood sugar (see below)
  • Blood Sugar Imbalances
    • increases Progesterone -> Androstenedione -> Estrone
      • Androstenedione is weak androgen
        • 5 times weaker than testosterone
        • competes with testosterone for binding on androgen receptors
      • Higher Estrone to testosterone balance
        • causes further insulin secretions in body
        • normal testosterone
      • Estrogen increases SHBG
        • decreases free testosterone
  • Impaired Liver Detoxification
    • impedes estrogen's breakdown
      • half life of testosterone: 7 minutes
      • half life of estrogen: hours
      • increases estrogen : testosterone ratio
  • Increased Dihydrotestoterone (DHT) production
    • 5-delta Desaturase converts testosterone to DHT
    • DHT has 10 times stronger infinity to receptor as compared to testosterone
      • leads to receptor resistance to testosterone
  • Dietary Deficiencies
    • Zinc
      • Low Zinc decreases testosterone production
      • Low stomach acid decreases absorption of zinc

Diagnostics

  • Get tested if you have symptoms of low testosterone
  • Many defects possible, creating low testosterone symptoms
    • many may not require hormone replacement
    • normal testosterone but low testosterone symptoms
  • Testosterone
  • Male hormone panel includes
    • total and free testosterone
    • estrogens (estrione, estradiol, estriol)
    • androstenedione
    • sex hormone binding globulin
    • DHEA
    • DHT
    • Luteinizing hormone.
    • Cortisol
      • Adrenal salivary panel
    • Salivary testing can be used for male hormones

See more information on Endogenous Testosterone and BPA and other Hormone Disruptors.


Main Menu | Hormone Menu | Exercise Physiology Titles