What is the purpose of the adrenal gland What are some impor

What is the purpose of the adrenal gland? What are some important hormones produced there? What are the clinical manifestations when someone has increased or decreased adrenal hormones?

Solution

Suprarenal or Adrenal glands are located on the top of each kidney as small, yellowish brown triangula structure. Each adrenal gland is enclosed in a connective tissue capsule and consists of two functionaly distinct parts:

a. A superficial yellowish part called suprarenal cortex. It secretes steroid hormones called adreno-corticosteroids or corticoids.

b. A deeper brownish part known as suprarenal medulla. It secretes catecholamines.

The different hormones secreted by these two parts of adrenal glands play a vital role in the body. Major hormones with their functional roles are as under.

1. Suprarenal cortex :- the suprarenal cortex comprises of following three zones :

(a) Zona glomerulosa :- It is the outermost zone. This zone secretes aldosterone, the mineralocorticosteroid. It is a salt retaining hormone. Its secretion is controlled by sodium level in the blood. A fall in sodium concentration or a rise in potassium conc. will stimulate its secretion. Aldosterone causes retention of Na⁺ and loss of K⁺ in the body by the action of renal tubules. It increases the reabsorption of water from the urine by the osmotic effect of Na⁺. Excess of aldosterone in the body may lead to hypertension due to excessive sodium retention.

(b) Zona fasciculata : It is the intermediate zone. The predominant hormone secreted by this zone is cortisol, the glucocorticosteroid. Cortisol ( hydrocortisone), corticosterone and cortisone are the main glucocorticoids. Glucocorticoids plays an important role in carbohydrate, lipid, protein and purine metabolism. They have influence on cardiovascular, skeletal muscle, central nervous system and other tissues. They exert strong anti- inflammatory effect and help to cope up with stress.

(c) Zona reticularis : It is the innermost zone. The main hormone secreted by this zone is adrenal androgens, sex hormones (androgens). These androgens are adrostenedione and dehydroepiandrosterone (DHEA). They are weak androgens compared to testicular androgens and are probably the major source of androgens in women. The sectretion of these hormones is stimulated by corticotropin (ACTH).

2. Suprarenal medulla. This part of adrenal gland helps the body to combat against stress or emergency conditions. Adrenalin and Noradrenalin are the chief hormones produced by the medulla. They are collectively called as catecholamines or emergency hormones. A sharp increase in the rate of release of these hormones occur during emergencies such as flight or fight reaction.

Disorders due to imbalance of cortical hormones

1. Hypofunction of adrenal cortex: Deficiency or malfunctioning of secretion of adrenal cortex results into Addison\'s disease characterised by muscular weakness, loss of weight and apetite, fatigue etc . Patients of this disease cannot tolerate stress well. Administration of cortisol brings improvement to the patient.

2. Hyperfunction of adrenal cortex: It results into Cushing\'s syndrome, hyperaldosteronism and adrenal virilism.

a. Cushing\'s syndrome :- This condition is characterised by redistribution of fat resulting in spindly arms and legs due to catabolism of muscle proteins accompanied by a rounded \" moon face\". For the cure doctors usually prescribe medications to decrese the cortisol production in the body.

b. Conn\'s syndrome ( Hyperaldosteronism) :- This disorder is characterised by increased Na and decreased K levels in the blood.The water increases the volume of the blood and causes hypertension resulting in muscular weakness, cramps and paralysis. Mainly the levels of sodium and potassium are targetted for the cure of this disorder.

c. Adrenal virilism:- Excess secretion of adrenal androgens. Growth of facial hairs in the female, temporal baldness, masculine features in a female etc are some symptoms of this disorder. Hormone suppressing medication is given.

Disturbances due to imbalances of adrenal medulla hormones

Chronic hypersecretion of adrenalin and noradrenalin occurs in case of tumours of Adrenal medulla, may result in drastic increase in blood pressure that may lead to cardiac failure or cerebral haemorrhage. Mainly tumour is operated and removed for the cure with other hormone supppressing medications.