The male sex hormone is called testosterone. It is produced in the testicles. Testosterone levels are important for normal sexual development and functioning in men. During puberty, it helps the development of male characteristics in boys such as body and facial hair, muscle mass, development of secondary sexual characteristics. Testosterone levels decline with age, so it is normal for older men to have low levels. Blood tests in some younger men show low testosterone levels. In this case we are talking about testosterone deficiency. The American Urological Association considers testosterone deficiency at levels below 300 nanograms per deciliter on two consecutive tests performed in the morning on an empty stomach. It is difficult to say how many men in the population have low testosterone levels, although overall data suggest that about 2 in 100 men are affected. Low testosterone is more common in men with diabetes or who are overweight. A research study has shown that about 30% of overweight men have low testosterone, compared to only 6.4% of those of normal weight. In some men, low testosterone levels can be due to accidental damage to the testicles, removal of a testicle due to cancer, chemotherapy or radiation, pituitary gland disorders, infections, autoimmune diseases. Basically, if your testicles produce less testosterone than normal, its blood level will drop. Many of these men are elderly or have conditions such as obesity, metabolic syndrome, which includes high blood pressure, high blood sugar, high cholesterol, or are taking antipsychotics. There are many signs and symptoms of testosterone deficiency. Specific symptoms are those that are more likely or directly related to this condition, such as: lack of sexual desire, reduced erectile function, hair loss. The American Urological Association recommends that clinicians perform screening tests for testosterone deficiency in men with unexplained anemia, bone loss, diabetes, patients before undergoing chemotherapy or radiation to the testes. One of the main methods of dealing with this condition is testosterone therapy. In some cases, such as Klinefelter’s syndrome or with surgically removed testicles, trauma, infection or other similar problem, it is highly recommended. Although the use of this type of therapy in men with testosterone deficiency due to, for example, aging, diabetes, infections and other similar conditions is not desirable due to the presence of side effects. Based on data from a number of clinical trials, there is an increased risk of heart disease and stroke for some men on testosterone therapy. Patients having some of the listed symptoms may even request testosterone therapy without even being tested.This action is not helpful and definitely not in their favor. The total testosterone level should always be tested before starting therapy. There are usually several different ways of administering testosterone: through the skin (transdermal), by injection, through the mouth (oral), or through the nose (intranasal). It is important to know that there is no evidence linking testosterone therapy with prostate cancer, there is no conclusive evidence that proves the formation of venous clots and testosterone therapy. Remember that every body is unique and every organism reacts differently to the applied treatment. Regular control of testosterone levels will be necessary, it is recommended that laboratory tests be done every 6-12 months.