Steroid Hormones

Steroid hormones are derived from cholesterol via a known metabolic pathway. The different steroid hormones differ only in the chemical bonds within the rings and modifications on the side chains. Steroid hormones are secreted from the adrenal cortex, testes and ovaries (also the placenta during pregnancy). They can be grouped into two classes corticosteroids and sex steroids, which can be further categorised based on the receptors to which they bind:

– Corticosteroids – glucocorticoids and mineralocorticoids
– Sex steroids – androgens, estrogens (oestrogen) and progestogens

Glucocorticoids are involved in the control and/or maintenance of many metabolic pathways and regulation of blood pressure. Cortisol, a key glucocorticoid, has many functions within the body including management of the stress response, regulation of metabolism, inflammatory and immune responses.

Mineralocorticoids, such as Aldosterone, are involved in maintenance of the balance between salts and water within the body.

Androgens, the male sex hormone, are responsible for development of secondary sex characteristics in males; the principle androgen, testosterone, is mainly produced in the testes (or the ovaries in women), with lower amounts being released by the adrenal cortex.

Estrogens are the female sex hormone and are responsible for the development of female sex characteristics in women. Estradiol (oestradiol) is the predominant estrogen and is mainly produced in the ovaries (testes in males) with secretion from the adrenal cortex being at a lower level.

Progestogens are responsible for maintenance of pregnancy. Progesterone, the principle progestogen, is secreted by the corpus luteum and makes the lining of the uterus receptive to implantation. Should pregnancy occur, the placenta will then become the primary source for progesterone production.