勃起能の回復 : ホルモン補充と勃起神経の再生

Erectile function of men is easily damaged by many factors such as aging, surgery, psychological stress and drugs. In this review, we discuss what is needed for recovery of erectile function in men whose function is damaged. We also refer to andropause and regeneration of nerves involved in erectile function. Questionnaire studies using non-biased protocols indicated that erectile function decreases with age. This has been confirmed by objective measurement of the maximum increase in penile circumference during nocturnal penile tumescence. Erectile dysfunction is found in approximately 5% of men in their 40s, 5-20% in their 50s, 20-40% in their 60s and 40-50% in their 70s. Although many factors are involved in the decline of erectile function, a decrease of the serum testosterone level may be one of them. Experimental studies have indicated that replacement of testosterone in aged rats restores sexual behavior depending on the dose and administration timing. The restoration by testosterone may be achieved through its action on the sexual center, the medical preoptic area (MPOA) in the hypothalamus, as well as that on peripheral nerves responsible for erectile function. The action seems to be partly mediated by nitric oxide and dopaminergic responses enhanced by testosterone in the MPOA. The results can be partly translated into treatment of partial androgen decline in the aged male (PADAM). PADAM includes a wide range of disease conditions such as psychological disorders, sexual dysfunction, muscle and bone diseases and abnormal lipid metabolism. Thus, testosterone replacement may be beneficial for quality of life of men. Finally, molecular findings on the injured cavernous nerve in rats help us understand its regeneration, which may be applicable in the clinical setting. While we need further study, our current results indicated that cavernous nerve regeneration may occur through nerve sprouting of the remaining intact nerves