Researchers at The University of Texas Southwestern Medical Center at Dallas are investigating the many facets of male infertility, but the research and the reasons couples are unable to conceive are complicated. If the male sexual organs are not where they should be or if any of the sexual machinery is not working at any one of a number of levels, this can cause male infertility. McPhaul studies androgen receptors, part of a complex biochemical pathway that stimulates activity of the male sex organs. The hormone androgen encourages development of male sex characteristics. Without androgen, sperm cannot develop, and sexual function does not exist.
Androgens target specific organs that have androgen receptors.
The two work together to trigger biochemical events regulated by testosterone in target cells. Spermatogenesis is a complex process initiated in spermatogonia, or immature stem cells, which eventually develop into either mature sperm or more stem cells for continued renewal. In humans, six stages comprise this development, and it takes about 16 days and 4.6 cycles for spermatogonia to become mature sperm. In a diagnostic work-up to determine why a man is infertile, we always look at the levels of hormones that are circulating in the blood to stimulate the gonads to make the sperm and the other products that are necessary for normal reproductive function. We need to know if there is a primary problem with the testes because of infection from late-onset mumps or some other illness or if there is another secondary problem like a pituitary tumor.