HSD17B4, or 17-beta-hydroxysteroid dehydrogenase type 4, is an enzyme that plays a crucial role in the metabolism of steroid hormones. It is involved in the conversion of inactive steroid precursors into their active forms, which are essential for various physiological processes in the body, including reproduction and metabolism. This enzyme is primarily found in the liver, kidneys, and adipose tissue. Mutations or deficiencies in HSD17B4 can lead to hormonal imbalances and are associated with certain medical conditions, such as adrenal disorders and infertility. Understanding HSD17B4 is important for developing treatments for these conditions.