Familial factors affecting prostatic cancer risk and plasma sex-steroid levels.

Whether familial factors affect the frequency of prostatic cancer and the plasma content of sex-steroids was investigated. Brothers (n = 257) of probands (n = 150) diagnosed with prostatic cancer before age 62 years had a fourfold higher risk for developing the disease than men in the general population in the State of Utah and their brothers-in-law (n = 202). Familial factors markedly affected the plasma content of sex steroids (testosterone, dihydrotestosterone, the ratio of testosterone to DHT, sex-hormone binding globulin, and the free fraction of testosterone) in nonendocrinologically treated probands and their brothers and sons and in normal men in the general populations. Index cases and their brothers and sons had a significantly lower mean plasma testosterone content than controls of comparable age. Preliminary data suggest that the metabolic clearance rate of testosterone and the conversion ratio of testosterone to estradiol are relatively high in probands. The observations indicate that familial factors are potent risk factors for the development of prostatic cancer. They also suggest that plasma androgen values in families with prostatic cancer cluster in the lower range of normal and that plasma sex-steroid content is more similar in each brothers with or without prostatic cancer than among nonbrothers.