ACTH stimulates growth of the adrenal cells and increases LDL receptors to amplify transport of cholesterol into the cells of the adrenal cortex which make adrenal steroids, where it accumulates since little can enter the mitochondria for conversion to steroid. Normally, adrenal steroids then signal their presence to the brain to moderate ACTH levels (feedback inhibition). However, in the absence of this, ACTH levels are elevated and cholesterol uptake by the cortical cells continues unabated. The adrenals become markedly enlarged (hyperplastic) by the accumulated lipid. Lipid accumulation is thought to damage the cells further (“second hit hypothesis”).