What Causes the Low Level of Testosterone?

Both progesterone and DHEA can be converted to androstenedione, which
is a precursor of testosterone. When progesterone and DHEA are running low, the testosterone level can drop sharply even in your twenties. The following factors can contribute to low testosterone, which become problems even in men in their twenties.
1. Stress: Research indicates that stress can lower testosterone levels temporarily because of lowered progesterone, causing functional impotence. This effect is reversible, but if stress continues for too long, structural changes will also follow.
2. Medications: Certain medications, such as those that treat high blood pressure, anxiety, and depression (including the tricyclics and the monoamine oxidase inhibitors) have been implicated in erectile dysfunction, decreased libido, and impaired ejaculation. Calcium channel blockers and acetylcholine esterase inhibitors cause a low incidence of erectile dysfunction. Although most high blood pressure medications have been associated with some kind of erectile impairment, diuretics seem to have little effect on erectile function. High blood pressure medications, which target the sympathetic nervous system, seldom cause impotence but may trigger retrograde ejaculation because they may relax the smooth muscles around the urethra and the bladder neck. Therefore, if one kind of blood pressure pill causes temporary impotence, you should try another kind. Generally, erectile dysfunction due to drugs that contain selective serotonin reuptake inhibitors should resolve after discontinuing the medications. However, in the 2008 issue of the Journal of Sex Medicine, Dr. Csoka et al. at the University of Pittsburgh reported three cases in which sexual dysfunctions such as low libido, the inability to achieve orgasm, the loss of sensation in the genital area, and erectile dysfunction did not return to normal after the patients stopped taking selective serotonin reuptake inhibitors (SSRIs).
3. Diabetes: High blood sugar levels damage the blood vessels and nerves distributed around the penis and cause poor circulation and nerve reflexes.
4. Alcohol: Estradiol is formed either from testosterone or from
androstenedione via estrone by an aromatase enzyme. Alcohol can enhance the function of aromatase, so if a man drinks too much alcohol, more and more of his testosterone can be converted into estradiol. That is why alcoholics lose their muscles and build their breasts and abdominal fat.
5. Poor diet: Healthy nerves are most important for normal erectile function and the lack of vitamins and minerals due to poor diet can cause neuropathy and impotence.
6. Aging: After 40 to 50 years old, testosterone normally decreases 1% every year. But for an unhealthy man, the process can accelerate, leading to a sharp decrease of testosterone levels, thus causing impotence.
7. Exercise: the more muscle a man builds, the higher level of testosterone a man can have.