Structure and Expression of a New Complementary DNA Encoding the Almost Exclusive 3β-Hydroxysteroid Dehydrogenase/Δ5-Δ4-Isomerase in Human Adrenals and Gonads

The study focused on the structure and expression of a new complementary DNA encoding the 3β-hydroxysteroid dehydrogenase/Δ5-Δ4 isomerase (3βHSD) enzyme, which is crucial for steroid hormone formation. Researchers identified a second type of 3βHSD cDNA, termed type II, which is predominantly expressed in human adrenal glands, ovaries, and testes, while type I is mainly found in the placenta and skin. The study revealed that type I has higher 3βHSD/Δ5-Δ4 isomerase activity compared to type II. The findings suggested that 3βHSD plays a significant role in the intracrine formation of sex steroids in peripheral tissues and could help understand the molecular basis of 3βHSD deficiencies, which are linked to congenital adrenal hyperplasia and androgen excess in women.