HSD17B3

The HSD17B3 gene provides instructions for making an enzyme called 17-beta hydroxysteroid dehydrogenase 3. This enzyme is active in the male gonads (testes), where it helps to produce the male sex hormone testosterone from a precursor hormone called androstenedione.

17-beta hydroxysteroid dehydrogenase 3 deficiency - caused by mutations in the HSD17B3 gene

More than 20 mutations that cause 17-beta hydroxysteroid dehydrogenase 3 deficiency have been identified in the HSD17B3 gene. In the Arab population of Gaza, where the condition is most common, almost all affected individuals have two copies of the same mutation. This mutation replaces the protein building block (amino acid) arginine with the amino acid glutamine at protein position 80 (written as Arg80Gln or R80Q).

Mutations in the HSD17B3 gene result in a 17-beta hydroxysteroid dehydrogenase 3 enzyme with little or no activity, reducing testosterone production. A shortage of testosterone affects the development of the reproductive tract in the male fetus, resulting in the abnormalities in the external sex organs that occur in 17-beta hydroxysteroid dehydrogenase 3 deficiency.