Late-onset hypogonadism in the aging male (LOH): definition, diagnostic and clinical aspects.

Late-onset hypogonadism (LOH) is defined by reduced serum testosterone levels (either total testosterone or free testosterone) and the careful exclusion of any form of classical hypogonadism. When the androgen decline associated with advancing age causes detrimental physiological and mental effects, the syndrome is known as symptomatic LOH (SLOH). A detailed medical history and physical examination are the bases of the diagnosis, and should always precede any biochemical investigations. A general screening of men above a certain age for testosterone deficiency is not feasible. Questionnaires may assist in identifying men who suffer from LOH. Common clinical symptoms of SLOH are lethargy, fatigue, decreased sense of well-being, reduced physical and mental activity, diminished libido, increased sweating, depressive mood, reduced muscle and bone mass or even osteoporosis, erectile dysfunction, and mild anemia. When clinical symptoms are present, the laboratory work-up should focus on total testosterone serum levels. Total testosterone levels <200 ng/dl indicate hypogonadism. In cases of testosterone levels between 200 and 400 ng/dl, measurement should be repeated and supplemented by determination of free testosterone, either by appropriate laboratory methods or the calculation of free testosterone index. In case of very low testosterone levels, classical secondary hypogonadism needs to be considered and excluded. For the safety reasons to exclude contraindications of therapy with androgens, and for follow-up investigations during therapy prostate-specific antigen (PSA), hemoglobin and hematocrit are of interest.