re: Testosterone

  • T produced by Leydig cells in the testes
  • T decline = hypogonadism. Causes:
    1. Leydig cells impaired or
    2. Control glands in the brain are not informing Leydig cells to produce enough T
  • For #1:
    • LH & FSH: hormones that exert influence over sex glands
    • When these levels are high, the pituitary is correctly trying to get T up, but it’s not happening, hence leydig failure. You would see low T and high FSH/LH in this situation
  • For #2:
    • T is low AND LH/FSH are low. The message to produce more T isn’t being sent. (CG is something to do in this scenario)
  • Aromatase converts T to estrogen and goes up w/ age. Too much estrogen can reduce production of T
  • Free T is 2-3% of total T
  • Estrogen high = SHBG high
  • T high = SHBG low
  • SHBG binds to T and limits free T
  • Can run into issues where injections spike T, but a disproportionate share is converted to estrogen, so the T to E ratio actually worsens even though total T is high
  • Patches/pellets may be superior because they don’t cause spikes