Once a doctor has diagnosed low testosterone on the basis of physical symptoms and medical test results, he/she should determine if the low testosterone levels are due to testicular, pituitary, or hypothalamic etiology. Individuals with low testosterone and normal or low serum LH levels may require further evaluation. After resolving these issues, treatment with supplemental testosterone can begin. Many studies have demonstrated improved function with testosterone replacement. Investigators have found that treatment resulted in increased sexual interest and an increased number of spontaneous erections. Men taking testosterone replacement therapy also were less depressed, angry, and fatigued. As seen in the accompanying chart, testosterone replacement therapy can be offered in a variety of forms. Together, the patient and his physician can select a mode of acceptable treatment. Pills
Although methyl testosterone is manufactured in capsule or pill form, it is not recommended for testosterone replacement in men because it is a weak androgen and not as effective as other preparations, and it has potentially serious adverse effects on the liver and lipids. When capsules/pills are swallowed and absorbed into the bloodstream, they are quickly broken down by the liver and do not achieve high enough blood levels to be useful unless given in large doses (40-50 mg/day). At these doses, they may cause adverse changes in blood lipids (fats) and liver damage. Testosterone undecanoate is moderately effective, but it must be given in capsular form three times daily. It has unique properties that reduce rapid metabolism by the liver and has not been associated with serious adverse effects on the liver. Injections
Deep muscle injections do not have to be taken daily but are instead given every 7-21 days. With injections, blood levels peak about two to three days after dosing and slowly decline during the next one to two weeks. The injections are painful, and fluctuations in serum levels of testosterone may be accompanied by changes in mood and a sense of well being. Injectable therapy usually is the least expensive way to provide testosterone replacement, and it requires the least patient motivation and compliance. Transdermal (through the skin) Delivery Systems
Gel and patch systems offer other advantages. Both are easy-to-apply systems that provide continuous delivery of testosterone. The water/alcohol mixture in the gel system dries quickly and the testosterone is readily absorbed into the skin, which serves as a reservoir for the sustained release of testosterone into the bloodstream. The site of application should be covered, or direct contact with women and children should be avoided. Skin reactivity with the gel seems to be limited in studies at the present time. Patches may cause local reactions in some patients. Most common complaints consist of itching or irritation and rarely blister formation at the application site and they may fall off when the individual sweats.

Buccal Testosterone Delivery System
A recently approved system, buccal testosterone treatment, provides a controlled and sustained release of testosterone through the buccal mucosa (tablet adheres to gum surface), where it is absorbed into the bloodstream. Tablets are replaced about every 12 hours. This system may cause gum or mouth irritation, bitter taste, gum pain or tenderness, headache, and taste perversion, but the majority of side effects were resolved within one to 14 days. Insignificant amounts of testosterone are present in the saliva, so transfer of testosterone to women and children in contact with saliva (e.g., with kissing or sharing of eating utensils) is negligible.