Abstract

There is no information on the relationship between endogenous pituitary and gonadal hormones and nocturnal penile tumescence (NPT) in healthy aging men. Sixty-seven married volunteers ages 45-74 years were studied in the sleep laboratory for 4 nights with the last night devoted to sequential blood sampling every 20 min. Bioavailable testosterone (bT) correlated significantly with several NPT measures while total testosterone, estradiol, LH, and prolactin were mostly unrelated to NPT. All bT-NPT correlations lost their significance after adjustment by multiple regression for the effect of age on both bT and NPT variables in the total subject sample. Analysis of bT-NPT relations by age groups revealed a significant association between bT and duration NPT in men ages 55 to 64 years, but no statistical relations in younger and older age groups. Changes in the central threshold of activation of NPT as age progresses may explain the age-dependent effect of bT in sleep erections.