Hormones. Cortical steroids (corticoids-hormones of adrenal cortex) are grouped into three catagories :
mineralocorticoids, glucocorticoids and gonadocorticoids.
(i) Mineralocorticoids. These hormones are secreted by the cells of zona glomerulosa of adrenal cortex.
- They are responsible for the regulation of mineral metabolism.
- Aldosterone (salt-retaining hormone) is the principal mineralocorticoid (90 to 95%) in humans. Aldosterone is a steroid.
- Its main function is to regulate the sodium content of the body. It is secreted when the sodium level is low.
- It acts on the kidneys to cause more sodium to be returned to the blood and more potassium to be excreted.
- As the sodium concentration in the blood increases, water follows it by osmosis, so the blood volume also increases.
- The effect of aldosterone is to increase both sodium and water in the blood.
Target cells. Mineralocorticoids act on the cells of the kidneys.
(ii) Glucocorticoids. They affect carbohydrate metabolism, however, they also affect the metabolism of proteins and fats.
- Glucocorticoids include three main hormones: Cortisol (= hydrocortisone), corticosterone and cortisone.
- Cortisol is the most abundant (about 95%).
- It stimulates the liver to synthesize carbohydrates from noncarbohydrates such as amino acids and glycerol. Thus increases level of glucose in the blood.
- Cortisol also stimulates the degradation of proteins within cells and amino acids in the blood, therefore, increases level of amino acids in the blood.
- Cortisol is to stimulate the breakdown of fats in adipose tissue and release fatty acids into the blood.
- Thus cortisol has anti insulin effect. It also helps in reducing pain.
- Cortisol is anti-inflammatory. It retards phagocytic acitivities of WBCs and thus suppresses 'inflammation reaction'.
- This hormone also reduces the number of mast cells, reducing secretion of histamine. This is also an antiinfammatory effect.
- Cortisol is also "immunosuppressive". It suppresses synthesis of antibodies by inhibiting the production of lymphocytes in the lymphoid tissues.
Target Cells. Glucocorticoids act on the cells of the liver.
(iii) Gonadocorticoids (Sexcorticoids). They are also called sex hormones of adrenal glands. Large quantities of male than female sexcorticoids (sex hormones) are produced.
- These male sex hormones are called androgens which are important in the development of a male foetus.
- Androgens stimulate the development of male secondary sexual characters like distribution of body hair.
- Female sex hormones secreted by the adrenal cortex are oestrogens which maintain the development of female secondary sexual characters.
Target cells. Gonadocorticoids act on the cells of gonads (testes and ovaries).