Corticosteroid

Corticosteroids (from Latin cortex = 'bark'; Greek stereos, στερεος = 'solid'), also known as corticoids, corticoids or cortins, are a group of about 50 steroid hormones formed in the adrenal cortex (the cortex of the adrenal gland) and chemically comparable synthetic substances. All corticoids are formed from the parent substance cholesterol. The common basic structure of the hormones is progesterone (Δ4-pregnene-3,20-dione).

Corticosteroids can be divided into three groups according to their biological effect or site of formation:

• Mineralocorticoids (main representative aldosterone) are formed in the zona glomerulosa of the adrenal cortex and mainly influence the potassium-sodium balance and thus the water content of the body.
• Glucocorticoids (main representative cortisol) are formed in the zona fasciculata of the adrenal cortex. They mediate important effects in glucose, lipid and protein metabolism.
• Androgens (main representative dehydroepiandrosterone (DHEA)) and estrogens are produced in the zona reticularis of the adrenal cortex.

Natural glucocorticoids include cortisone, corticosterone and cortisol; mineralocorticoids include aldosterone and deoxycorticosterone, which was isolated by Reichstein as early as 1935. Synthetic corticoids are e.g. prednisone and prednisolone, methylprednisolone, triamcinolone, dexamethasone, betamethasone and paramethasone.

Synthesis

The different hormones are formed from progesterone by hydroxylation (incorporation of OH groups) and oxidation of these groups to keto or aldehyde groups at different positions. The synthesis and secretion of the androgens and glucocorticoids is stimulated by ACTH (corticotropin) from the adenohypophysis (anterior lobe of the pituitary gland). The synthesis and secretion of mineralocorticoids is stimulated by angiotensin II and potassium.

Effect

As lipophilic hormones, corticosteroids act on receptors in the cytosol and nucleus, to which they can freely diffuse through the cell membrane. Meanwhile, however, the existence of membrane-bound receptors for corticosteroids is also assumed and researched. The receptors in the cell interior can be divided into two types. Type I is specific for mineral corticoids and type II for glucocorticoids. The specificity of the receptors seems to depend on the activity of 11β-hydroxysteroid dehydrogenase 1, which occurs by dehydrogenation of the β-OH group at the C11atom. This renders the corticoids (with the exception of aldosterone) ineffective. Excessive consumption of licorice may inhibit 11-hydroxysteroid dehydrogenase, leading to stronger effects of the mineral corticoids.