Spermatogenesis cycle shorter than previously thought

August 15, 2005

Advances in the field of male infertility continue to provide insight into the factors and processes that make fertility possible. Ultimately, the advances lead to techniques that extend the possibility of fertility to an ever-increasing population of patients.

Advances in the field of male infertility continue to provide insight into the factors and processes that make fertility possible. Ultimately, the advances lead to techniques that extend the possibility of fertility to an ever-increasing population of patients.

A study involving stable nontoxic isotope labeling to assess germ cell turnover time in vivo suggested that the spermatogenesis cycle is less than 50 days, considerably briefer than generally assumed.

Older estimates of the spermatogenesis cycle were developed from evaluation of static slides. In this study, men ingested deuterated water, and investigators waited until it appeared in sperm, a simple kinetic method to determine the spermatogenesis cycle.

"With the exception of one outlier, Paul Turek, MD, and co-investigators found that the cycle of spermatogenesis is much shorter than we thought, only about 2 months," Dr. Niederberger said. "That is a terrific piece of information that came about from the use of modern technology to come up with a highly clinically relevant outcome."

Androgen therapy for andropause symptoms is an under-appreciated cause of subfertility, particularly in older men. Physicians need to be aware of this risk factor when evaluating patients with subfertility.

One of the most discussed issues in medicine today is endocrine changes in the aging male. In a sense, the issue is similar to endocrine changes in the aging female. The trajectory of treating the aging female involved four generations. The first generation involved gathering data and learning about endocrine dysfunction in the female. The second generation was treatment of the problem. The third generation was to determine whether any adverse events are associated with the treatment, and the fourth is modulation of endocrine therapy on the basis of what is currently known.

In men, the trajectory is still in first generation, or perhaps just beginning to enter the second generation. Clinicians are just beginning to recognize that male aging is associated with dysfunction, similar to what is seen in the aging female. The dysfunction includes bone demineralization, erectile dysfunction, loss of libido, loss of energy levels, increased depression, decreased muscle mass, and increased fat mass. All of these changes are thought to be associated with the decline of testosterone.

To address this dysfunction in the aging male, clinicians have begun to treat men with exogenous testosterone, which is an effective way to get rid of sperm. Some of the men treated with exogenous testosterone are still interested in having children, and these men are being detected in fertility clinics, as identified Eric Gwynn, MD, and Dominick Carbone, MD.

"The moral of the story is that we need to educate primary care physicians and endocrinologists-physicians who treat the aging male-to ask about reproduction because they can't just take for granted that a 60-year-old man doesn't want to have kids," said Dr. Niederberger.

Accumulating data suggest that varicocelectomy can improve human sperm DNA integrity. The data support the beneficial effect of varicocelectomy on human spermatogenesis.

Varicocele is the most common identifiable cause of male reproductive dysfunction. Yet understanding of varicocele re-mains incomplete. Varicocele is thought to interfere with countercurrent heat exchange mechanisms that cool the testis, damaging the sperm's reproductive function.

Semen analysis is not a particularly good test of male reproductive function, and in men with varicocele, semen analysis might not accurately reflect the degree of reproductive dysfunction. New tools have been developed to study the reproductive function of the sperm, and some of those new tools address DNA integrity. A reasonable question to ask is whether varicocelectomy improves DNA integrity.