Role of lipoproteins in steroidogenesis

Although cholesterol is accepted as the major precursor of steroid hormones as a result of side-chain cleavage to pregnenolone (see below), research over the past decade or so has focused on the mechanisms by which steroidogenic tissues obtain cholesterol. It should be borne in mind that such tissues require cholesterol, not only for steroid synthesis but also for membrane synthesis, and hence require more of the precursor sterol than other tissues. Morris and Chaikoff [1] showed that the bulk of rat adrenal cholesterol was derived from circulating cholesterol, and later work revealed a similar state of affairs in humans. 

Cholesterol appears to be taken up from plasma lipoproteins by steroidogenic tissues by two receptor-mediated pathways - the LDL pathway and the HDL pathway. Not all tissues of all species can utilise both of these thus, the LDL pathway appears to occur in all species, including man, whereas the HDL pathway occurs mainly in rodents. LDL lipoproteins interact specifically with cell surface-bound receptors, as shown for, e.g., adrenal [9] and ovary [10], after which internalization occurs by endocytosis and hydrolysis of LDLs, plus their cholesterol ester complement by lysosomal action. 

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Gwynne JT, Strauss JF III The role of lipoprotein in steroidogenesis and cholesterol metabolism in steroidogenic glands. Endocr Rev 1982 3 299-329. 

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