A certain proportion of middle-aged and elderly men have total testosterone concentrations below the reference range for young adult males. Possible consequences of reduced androgen levels include fat mass gain, loss of muscle and bone mass, fatigue, depression, anaemia, poor libido and erectile dysfunction. The clinical features of androgen deficiency in the aging male (ADAM) resemble those of hypogonadism of younger subjects, with a single relevant difference: each of these features can also occur in elderly men with normal androgen levels.