To continue the discussion of causes of erectile dysfunction, we were focusing on situations that would result in the testicle producing less testosterone, the male hormone. This is also known as primary hypogonadism (the prefix, hypo-, means low, and the word gonad is another term for sex organ). Testosterone is responsible for giving men their sex drive and contributes to producing an erection. I sometimes tell my patients that, "if the tank is not full, the car will not run." This is equating testosterone with the car's gasoline, of course. If the blood level of testosterone is not high enough, men can suffer from erectile dysfunction.
Other problems that may affect the testicle's ability to produce testosterone are trauma or exposure to infection or chemotherapy. If the testicle is injured (sports injury, penetrating trauma) the blood flow to the testicle can be harmed or a scar can develop such that the function decreases (lower testosterone production). An infection of the testicle such as mumps orchitis can lead to scar formation as well and diminish the overall testicular function. Chemotherapy for the treatment of cancer can also damage testicular cells. These medications typically will affect cells that are actively multiplying (testicular cells) and this can lead to the lower sperm and testosterone production. Often this is not permanent, but it can be.
Remember that the testicular cells take their orders from the pituitary gland and the hypothalamus in the brain. Other causes of low testosterone can occur when these organs are damaged. This is known as secondary hypogonadism. If there is no "order" to make the hormone testosterone, the cells are inactive. Diseases that can lead to this problem are a brain tumor that is in the area of the pituitary, infections such as HIV and AIDS, some medications, and even obesity.
Testing to determine these types of dysfunction usually will start with a testosterone level. Testosterone floats around in the blood bound to protein or unbound, so-called "free testosterone." Often both levels are drawn. The free testosterone is the active testosterone.
Other hormonal levels that may be drawn often include leutenizing hormone (LH) (this is the hormone that comes from the brain and gives the command to make testosterone) and prolactin. If fertility is an issue, a semen analysis can be done. To determine if there is problem with the pituitary, a computerized tomography or CT can be done of the head. Finally, sometimes a testicular biopsy is needed.