Late-onset hypogonadism

Late-onset hypogonadism (LOH) or testosterone deficiency syndrome (TDS) is a condition in older men characterized by measurably low testosterone levels and clinical symptoms mostly of a sexual nature, including decreased desire for sex, fewer spontaneous erections, and erectile dysfunction. It is the result of a gradual drop in testosterone; a steady decline in testosterone levels of about 1% per year can happen and is well documented in both men and women. Some men present with symptoms, but they have normal testosterone levels, while others with low testosterone levels have no symptoms. The reasons for this phenomenon are currently unknown. In their late 40s and early 50s, some men may experience depression, loss of libido, erectile dysfunction, and other physical and emotional symptoms. These symptoms include irritability, loss of muscle mass and reduced ability to exercise, weight gain, lack of energy, difficulty sleeping, or poor concentration. It is important to note that many of these symptoms may arise from a midlife crisis or as the results of a long-term unhealthy lifestyle (smoking, excess drinking, overeating, lack of exercise) and may be best addressed by lifestyle changes, therapy, or antidepressants. Testosterone levels are well-documented to decline with aging at about 1% per year in both men and women after a certain age; the causes are not well understood. As of 2016, the International Society for the Study of the Aging Male defines late-onset hypogonadism as a series of symptoms in older adults related to testosterone deficiency that combines features of both primary and secondary hypogonadism; the European Male Aging Study (a prospective study of ~3000 men) defined the condition by the presence of at least three sexual symptoms (e.g. reduced libido, reduced spontaneous erections, and erectile dysfunction) and total testosterone concentrations less than 11 nmol/L (3.2 ng/mL) and free testosterone concentrations less than 220 pmol/L (64 pg/mL).