Low Sperm Count May Be Associated with Prenatal Testosterone Excess

Exposure to an excess of sexual steroids, like testosterone, during fetal development may be a potential risk factor for low sperm count and motility, according to a new study accepted for publication in Endocrinology, a journal of The Endocrine Society.

“The majority of disorders affecting sperm count in humans are originated during fetal life,” said Professor Sergio Recabarren of the University of Concepcion in Chillan, Chile and lead author of the study. “A developing fetus is very vulnerable to its environment, and when that environment is exposed to excess sexual steroids, it may have a significant deleterious effect on a male offspring’s fertility.”

Prenatal exposure to excess sexual steroids can occur in two ways, said Dr. Recabarren. First, the exposure may be a product of increased sexual steroids in the maternal environment due to a hormonal condition such as polycystic ovary syndrome. Second, humans are exposed to several industrial pollutants which can act as steroid mimics, causing the body to inhibit or accelerate native steroid production.

In this study, researchers treated pregnant sheep with 30 mg testosterone propionate twice weekly from days 30 to 90 of pregnancy and with 40 mg testosterone propionate from days 90 to 120 of pregnancy. They found a significant reduction in body weight, scrotal circumference, and sperm count in male sheep born to these mothers compared with control sheep.

“While this research involved sheep, it can certainly be argued that in humans, exposure to an excess of sexual steroids during fetal development could constitute a potential risk factor that may conduct to a low sperm count,” said Dr. Recabarren.

Low sperm counts are also associated with testicular cancer, with an incidence rate 20 fold higher than men with normal sperm analysis, said Dr. Recabarren. The findings from this study highlight growing concerns of the detrimental effects of prenatal steroid excess on reduced sperm counts.

Other researchers working on the study include Pedro Rojas-Garcia, Monica Recabarren, and Victor Alfaro of the University of Concepcion in Chillan, Chile; Rosita Smith and Teresa Sir-Petermann of the University of Chile in Santiago; and Vasantha Padmanabhan of the University of Michigan in Ann Arbor.

A rapid release version of this article, “Prenatal Testosterone Excess Reduces Sperm Count and Motility,” has been published on-line and will appear in the December issue of Endocrinology.

Founded in 1916, The Endocrine Society is the world’s oldest, largest, and most active organization devoted to research on hormones, and the clinical practice of endocrinology. Today, The Endocrine Society’s membership consists of over 14,000 scientists, physicians, educators, nurses and students in more than 80 countries. Together, these members represent all basic, applied, and clinical interests in endocrinology. The Endocrine Society is based in Chevy Chase, Maryland.