How is cholesterol converted into pregnenolone in cells?

The conversion of cholesterol into pregnenolone is the essential first step in the synthesis of all steroid hormones. This process takes place within the mitochondria of endocrine cells located in the adrenal glands and the gonads (ovaries and testes).1

The reaction is mediated by a specific cleavage enzyme. The synthesis of this enzyme is regulated by hormonal signals: in the adrenal glands, it is stimulated by corticotropin (ACTH) or angiotensin, while in the gonads, it is stimulated by follicle-stimulating hormone (FSH) and luteinizing hormone. Once pregnenolone is formed, it is transported out of the mitochondria and into the endoplasmic reticulum to undergo further enzymatic conversion into progesterone and subsequently into other specific steroid hormones.1