Hypogonadism is the medical name for a condition in which levels of the hormones which control sexual development are lower than normal. There are dozens of different causes of hypogonadism. Many people with hypogonadism have a change in a gene. There are many genes that give instructions for the hormones important for sexual development. Changes in one of these genes that stops the gene from working, can cause hypogonadism. In some of these medical conditions, there are additional features such as learning problems. In this study we will search databases to find all the genetic conditions that can be associated with hypogonadism. We will ask a number of people with changes in certain genes, identified from our search, to come to our research clinic. We will ask them about their health and examine them for signs of hypogonadism. For some, we will take blood samples to test for hypogonadism. This project will help us understand how common hypogonadism is, in people with these genetic changes, which will help with their treatment.