Hypogonadism is endocrinopathy caused by the reduced secretion and action of testosterone (T) in men. Late hypogonadism (LOH, Late Onset Hypogonadism) is expected in aging men. Until recently, nor its pathogenesis, or frequency are known. Meanwhile, the most comprehensive to date prospective clinical studies EMAS (European Male Ageing Study) conducted on 3369 subjects showed that age -related decline in T is smaller than suspected. In the range of 40 to 79 years of age the total T level decreases of 0.4% and free T 1.3% per year. Mental and physical symptoms, regarded as typical for LOH, have no connection with the lower level of T. Reduction of the level of T in older men corresponds to the reduced luteinizing hormone (LH) secretion in obesity (secondary hypogonadism) and testicular defi ciency (primary hypogonadism), which can also be present at the systemic diseases. Th e modern defi nition of LOH is the presence of three sexual symptoms (lack of sexual thoughts, no morning erections and loss of erection) and the level of blood T