X-linked adrenal hypoplasia congenita is caused by mutations in the NR0B1 gene. More than 90 NR0B1 mutations that cause X-linked adrenal hypoplasia congenita have been identified. Many of these mutations delete all or part of the NR0B1 gene, preventing the production of DAX1 protein. Some mutations cause the production of an abnormally short protein. Other mutations cause a change in one of the building blocks (amino acids) of DAX1. These mutations are thought to result in a misshapen, nonfunctional protein. Loss of DAX1 function leads to adrenal insufficiency and hypogonadotropic hypogonadism, which are the main characteristics of this disorder.