Life Cycle of a Penis

By David Freeman
WebMD Feature

Reviewed by Louise Chang, MD

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.

Goldstein explains that another mechanism involves the gradual buildup of relatively inelastic collagen (scar tissue) within the stretchy fibrous sheath that surrounds the erection chambers. Erections occur when these chambers fill with blood. Blockages within the penile arteries -- and increasingly inelastic chambers -- mean smaller erections.

As penis size changes, so do the testicles. "Starting around age 40, the testicles definitely begin to shrink," says Goldstein. The testicles of a 30-year-old man might measure 3 centimeters in diameter, he says; those of a 60-year-old, perhaps only 2 centimeters.

Curvature. If penile scar tissue accumulates unevenly, the penis can become curved. This condition, known as Peyronie's disease, occurs most commonly in middle age. It can cause painful erections and make intercourse difficult. The condition may require surgery.

Sensitivity. Numerous studies have shown that the penis becomes less sensitive over time. This can make it hard to achieve an erection and to have an orgasm. Whether it renders orgasm less pleasurable remains an open question.

If there's a silver lining to these presumably unwelcome changes, it's this: Experts say these changes need not ruin your erotic life. One recent study involving 2,213 men in Olmstead County, Minn., showed significant declines in erectile function, libido, and ejaculatory function -- but only moderate decreases in sexual satisfaction. "Older men may be less likely to perceive these declines as a problem and be dissatisfied," concluded the study's authors.

As Goldstein puts it, "The most important ingredient for a satisfying sex life is the ability to satisfy your partner, and that doesn't require peak sexual performance or a big penis. As long as a man's partner enjoys sexual intercourse, he feels like a god."