Life Cycle of a Penis

It's no secret that a man's sexual function declines with age. As his testosterone level falls, it takes more to arouse him. Once aroused, he takes longer to get an erection and to achieve orgasm and, following orgasm, to become aroused again. Age brings marked declines in semen volume and sperm quality. Erectile dysfunction (ED), or impotence, is clearly linked to advancing years; between the ages of 40 and 70, the percentage of potent men falls from 60% to roughly 30%, studies show.

Men also experience a gradual decline in urinary function. Studies show that a man's urine stream weakens over time, the consequence of weakened bladder muscles and, in many cases, prostate enlargement.

And that's not all. Recent research confirms what men have long suspected and, in some cases, feared: that the penis itself undergoes significant changes as a man moves from his sexual prime -- around age 30 for most guys -- into middle age and on to his dotage. These changes include:

Appearance. There are two major changes. The head of the penis (glans) gradually loses its purplish color, the result of reduced blood flow. And there is a slow loss of pubic hair. "As testosterone wanes, the penis gradually reverts to its prepubertal, mostly hairless, state," says Irwin Goldstein, MD, director of sexual medicine at Alvarado Hospital in San Diego and editor-in-chief of The Journal of Sexual Medicine.

Penis Size.  Weight gain is common as men grow older. As fat accumulates on the lower abdomen, the apparent size of the penis changes. "A large prepubic fat pad makes the penile shaft look shorter," says Ira Sharlip, MD, clinical professor of urology at the University of California, San Francisco.

"In some cases, abdominal fat all but buries the penis," says Ronald Tamler, MD, PhD, co-director of the Men's Health Program at Mount Sinai Hospital in New York City. "One way I motivate my overweight patients is by telling them that they can appear to gain up to an inch in size simply by losing weight."

In addition to this apparent shrinkage (which is reversible) the penis tends to undergo an actual (and irreversible) reduction in size. The reduction -- in both length and thickness -- typically isn't dramatic but may be noticeable. "If a man's erect penis is 6 inches long when he is in his 30s, it might be 5 or 5-and-a-half inches when he reaches his 60s or 70s," says Goldstein.

What causes the penis to shrink? At least two mechanisms are involved, experts say. One is the slow deposition of fatty substances (plaques) inside tiny arteries in the penis, which impairs blood flow to the organ. This process, known as atherosclerosis, is the same one that contributes to blockages inside the coronary arteries -- a leading cause of heart attack.