- T produced by Leydig cells in the testes
- T decline = hypogonadism. Causes:
- Leydig cells impaired or
- 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