[Study on nocturnal penile tumescence (NPT) in healthy males study on age-related changes of NPT]

Nocturnal penile tumescence (NPT) occurs in all healthy males as a physiological phenomenon. Male sexual function can be evaluated by NPT. However, the age dependent changes and the significance of NPT have still remained unknown. Thus, we measured NPT throughout the night in healthy 189 subjects, ranging from 3 to 84 years old, and studied the relationship between this phenomenon and age. The parameters obtained by NPT appeared to be greater in men over about 10 years old. This increase of the parameters was related to the maturation of the hypothalamo-pituitary-testicular axis, which starts rapidly at puberty. A significant decrease in the total tumescence time in men over 30 years of age was related to a decrease of androgen. In men over 55 years of age, the maximum penile circumference change and the maximum increase rate in penile circumference were significantly lower than those of men in their twenties. These results suggest that the decrease in the parameters of NPT in men over 55 years of age had a relationship with the decrease of androgen, and organic changes in the corpus cavernosum and penile vascular system that occurred with aging. In conclusion, NPT may be related to the sexual maturation and decline in men. We also provide standard reference parameters for NPT in Japanese, which could be useful in the diagnosis and treatment of male sexual dysfunction.