Testosterone has several positive effects on sexual function, but its most significant effect is on libido, sexual interest and arousal. Boys going through puberty develop an enhanced interest in sex (thoughts, fantasies, masturbation, intercourse) as a consequence of rising levels of testosterone. Hypogonadal men usually have a significant improvement in libido when TRT is initiated (Wang et al 2000; Morley and Perry 2003).
Any day that you don’t get 20 minutes of direct sunlight on your skin, you want to supplement with 5,000 IUs of vitamin D3. If you get your blood levels tested and you’re extremely low — below 50 IUs — you typically want to do 5,000 IUs twice a day for three months until you get those numbers up. You can do everything in the world, but if your vitamin D levels aren’t right, your testosterone levels will stay low.
One study found that men who took 3,332 international units (IU) of vitamin D daily for one year significantly increased their testosterone levels. But vitamin D supplements may only work for men who are severely deficient in this specific vitamin. Another study found that men without a vitamin D deficiency had no increase in testosterone levels after taking vitamin D.
Testosterone levels generally peak during adolescence and early adulthood. As you get older, your testosterone level gradually declines — typically about 1 percent a year after age 30 or 40. It is important to determine in older men if a low testosterone level is simply due to the decline of normal aging or if it is due to a disease (hypogonadism).