Adrenal glands are the two conical structures placed on the top of each kidney and, hence are also called suprarenals. Each adrenal gland is made up of two regions – the outer, yellow adrenal cortex and inner, reddish brown adrenal medulla. Each gland secretes separate and different hormones.
Adrenal Cortex: It secretes three hormones – glucocorticoids regulate carbohydrate, protein and fat metabolisms, mineralcorticoids regulate the metabolism of sodium and potassium and sex steroids which have only mild androgenic effects.
The decreased activity of adrenal cortex hormones produces Addison’s disease characterized by bronzing of the skin, low blood pressure, dehydration of the body, irritability etc. Excessive secretion of adrenal corticosteroids produces high blood pressure, rise in sodium concentration in blood plasma, high blood sugar in urine, appearance of male secondary sexual characters in female, etc and this is called Cushing’s syndrome.
Adrenal medulla: The adrenal medulla produces adrenalin (epinephrine) and nor-adrenalin (nor-epinephrine). These hormones help the body to combat stress and face emergency conditions. During fall in blood sugar, pain, cold or injury, the adrenal medulla and sympathetic nervous system are stimulated. Hence, adrenal medulla is called gland of emergencies. Nor-epinephrine also acts as a neuro transmitter.