For gentlemen only: Your fertility may be dictated by your skeleton. New research in mice has shown that there's a very strong link between the bone hormone osteocalcin, and the production of testosterone. Male mice with low levels of osteocalcin had small and infrequent litters compared to those with higher amounts of the hormone (lower testosterone levels lead to lower sperm counts). If the relationship holds true in humans, it's thought that this could lead to a new generation of drugs to help combat poorly understood male infertility problems.
Research published in Cell