Figure 1. The biosynthetic pathway for the production of steroid hormones from plasma cholesterol. Cholesterol is first converted to pregnenolone, which serves as a prohormone (i.e. precursor) for all other steroid hormones. Relevant enzymes are depicted in italics. HSD, hydroxysteroid dehydrogenase.

Figure 2. Interaction between a steroid hormone and its receptor. The lipid-soluble steroid passes through the cellular membrane and enters the target cell. Subsequently, the steroid molecule enters the cell nucleus and binds to its receptor. The binding of the steroid to its receptor causes the DNA binding domain of the receptor protein to dissociate from a heat-shock protein (HSP). Following dissociation from the HSP, the hormone–receptor complex binds to an acceptor site on the DNA and initiates a process whereby a gene is transcribed into mRNA. The mRNA then exits the nucleus and serves as a template for protein synthesis on the ribosomes of the rough endoplasmic reticulum (ER).

Figure 3. The process of sexual differentiation in mammalian vertebrates. This diagram highlights the importance of hormones in regulating the sexual differentiation of both secondary sexual characteristics and behaviour. Additional details on the process of sexual differentiation can be found in the text.