[Diagnosis of the "aging male"--what is recommended?].

Aging is a complex process. In males after the 40th year of life the total serum testosterone (T) levels are decreased, especially the serum levels of so-called bioavailable testosterone (BT), whereas the serum levels of sex hormone binding globulin (SHBG) are increased. This androgen deficiency in males does not always cause symptoms. In symptomatic males a detailed history is required supported by screening questionnaires for androgen deficiency, followed by a clinical examination; the serum levels of T and SHBG should also be determined. In patients with normal serum levels of T and increased SHBG serum levels, free testosterone, obtained by calculation from the T and SHBG levels, is a reliable and simple index of BT to show the presence of androgen deficiency. Further endocrinological examinations are only recommended for differential diagnosis in the aging male. Before testosterone replacement therapy is started in symptomatic males with hypogonadism, risk factors, especially cancer of the prostate, have to be excluded.