When a couple has trouble conceiving, it's often the woman who chooses to undergo a reproductive procedure, such as artificial insemination or in vitro fertilization (IVF), which is actually multiple procedures. Even if the issue lies with the man, which it does in more than one-third of infertility cases, women are often subjected to testing first.

If researchers in Denmark and the United States are correct, this process is about to change, at least in cases where sperm quality is the issue.

A coincidental discovery of a protein called RANKL in testicles got researchers thinking: If RANKL can cause the degradation of bones, where it is most often present, and lead to osteoporosis, maybe it is a cause of poor