What are the genetic changes related to Leydig cell hypoplasia ?
Mutations in the LHCGR gene cause Leydig cell hypoplasia. The LHCGR gene provides instructions for making a protein called the luteinizing hormone/chorionic gonadotropin receptor. Receptor proteins have specific sites into which certain other proteins, called ligands, fit like keys into locks. Together, ligands and their receptors trigger signals that affect cell development and function.  The protein produced from the LHCGR gene acts as a receptor for two ligands: luteinizing hormone and a similar hormone called chorionic gonadotropin. The receptor allows the body to respond appropriately to these hormones. In males, chorionic gonadotropin stimulates the development of cells in the testes called Leydig cells, and luteinizing hormone triggers these cells to produce androgens. Androgens, including testosterone, are the hormones that control male sexual development and reproduction. In females, luteinizing hormone triggers the release of egg cells from the ovary (ovulation). Chorionic gonadotropin is produced during pregnancy and helps maintain conditions necessary for the pregnancy to continue.  The LHCGR gene mutations that cause Leydig cell hypoplasia disrupt luteinizing hormone/chorionic gonadotropin receptor function, impeding the body's ability to react to these hormones. In males, the mutations result in poorly developed or absent Leydig cells and impaired production of testosterone. A lack of testosterone interferes with the development of male reproductive organs before birth and the changes that appear at puberty. Mutations that prevent the production of any functional receptor protein cause the more severe features of Leydig cell hypoplasia, and mutations that allow some receptor protein function cause milder signs and symptoms.