The science of steroids
These fat-based chemical signals send vital messages across the body
Steroid hormones are a group of chemical messages made from cholesterol. This fatty, waxy substance has four conjoined rings in its structure, and this forms the backbone of five types of long-range chemical signals. Produced in one part of the body, steroid hormones carry messages to the target cells via the bloodstream.
The first type are glucocorticoids, including the stress hormone, cortisol. Made in the adrenal glands above the kidneys, it affects cells all over the body, reducing inflammation and controlling blood sugar and metabolism.
The second type are mineralocorticoids, the most important of which is aldosterone. Also made in the adrenal glands, it sends messages to the kidneys to control the body’s fluid levels. Without aldosterone, the amount of salt and water in the body drops and potassium rises. This affects the heartbeat, which relies on the right amount of salts.
The third type are the androgens, the male sex hormones. The most active is testosterone, produced in the testes during and after puberty. Testosterone causes hair growth and changes to the vocal cords, bones, muscles and reproductive organs. The ovaries also make testosterone but in smaller amounts.
The fourth and fifth types of steroid hormones are the oestrogens and progestogens, the female sex hormones. Made by the ovaries, they work with hormones from the pituitary gland to control the menstrual cycle. Oestrogen rises during the first half of each cycle, and progesterone takes over for the second half, preparing the body for pregnancy.