"Thyroid is needed for the adrenals to function well, and adequate cholesterol, as raw material. It's popular to talk about 'weak adrenals,' but the adrenal cortex regenerates very well. Animal experimenters can make animals that lack the adrenal medulla by scooping out everything inside the adrenal capsule, and the remaining cells quickly regenerate the steroid producing tissues, the cortex. So I think the 'low adrenal' people are simply low thyroid, or deficient in cholesterol or nutrients." —Raymond Peat, PhD