A unified homeostatic system of cholesterol and steroid hormone pathways is described, in which the uses or modulations of function of the homeostatic system of cholesterol and steroid hormone pathways are linked by lipoproteins, and are used or modulated to achieve a therapeutic benefit, to diagnose a disease or medical condition in humans, or to develop suitable active agents or combinations of active agents. Pharmaceutical compositions, methods of treatment, methods of drug development, and assay methods that rely on the new understanding of the homeostatic system are described.
