Lab

Total Testosterone

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Total Testosterone, Serum Testosterone, Testosterone Level, Serum Total Testosterone, Testosterone

  • See Also
  1. Free Testosterone
  2. Androgen Decline in the Aging Male
  3. Testicular Failure
  4. Hypogonadism
  • Physiology
  1. Androgenic steroid synthesized in males, in the leydig cells of the Testis
  2. Release is stimulated by Luteinizing Hormone release from the Pituitary Gland
    1. In a negative feedback loop, Testosterone suppresses release of LF and FSH from the pituitary
  3. Mechanism
    1. Activity via Testosterone, or by its conversion to dihydrotestosterone (DHT) irreversibly by 5-alpha reductase
  4. Responsible for male sex characteristics and male reproductive function
    1. Facial hair
    2. Deep voice
    3. Muscle growth
    4. Spermatogenesis
    5. Libido
  • Pathophysiology
  1. Low Levels
    1. See Male Hypogonadism
    2. See Androgen Decline in the Aging Male
  2. Elevated Levels
    1. See Precocious Puberty
    2. See Anabolic Steroid
  • Technique
  1. Obtain in the morning (or within 2 hours of awakening) due to circadian variation
  • Labs
  • Interpretation
  1. Normal Levels
    1. Male: 300 to 1000 ng/100 ml
    2. Female: <70 ng/100 ml