The steroid hormones are synthesized in the adrenal cortex, the gonads, and the placenta; are all derived from cholesterol and many are of clinical importance. Steroid hormones are synthesized in the mitochondria and smooth endoplasmic reticulum. Because they are lipophilic, they cannot be stored in vesicles from which they would diffuse easily and are therefore synthesized when needed as precursors. Upon stimulation of the parent cell, steroid hormone precursors are converted to active hormones and diffuse out of the parent cell by simple diffusion as their intracellular concentration rises
