الفهرس 
Anatomy and physiology of adrenal glandOnly 14 pages are availabe for public view
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Abstract
The adrenal gland is composed of adrenal cortex and medulla. The adrenal cortex secretes three types of hormones: glucocorticoids, mineralocorticoids and sex hormones. The adrenal cortex is essential to life. It participates in responses to stresses and through its chief hormones influences the metabolism of carbohydrates, proteins, fat, electrolytes and water. Adrenocorticotrophic hormone (ACTH) stimulates the synthesis of cortisol and 17-ketosteroids by adrenal cortex. Three factors are of major importance in regulating ACTH, first is homeostatic negative feed back inhibition of ACTH secretion by circulating cortisol, second, is plasma circadian rhythm with high level in the early morning and low level late in the evening. Third factor is stress, thus plasma ACTH levels are increased during fever, trauma or surgery resulting in increased secretion of cortisol.
The synthesis and secretion of adrenal mineralocorticoids are dependent primarily upon the renin angiotensin system.
The active principles of adrenal medulla are the catecholamines which include adrenaline 80% and noradrenaline 20%.
The catecholamines exerts their effects on target organs by binding to receptors sites. Epinephrine has both alpha and beta effects. Norepinephrine has mainly alpha effect. Adrenal medulla is the only endocrine gland which is under nervous control. When the peripheral end of the splanchnic nerve is stimulated adrenaline and noradrenaline are liberated.
The main disorders of adrenal gland include either: (1) excess secretion of corticosteroid (cushing syndrome). The patient presents mainly with centripetal obesity, hypertension, osteoporosis and glucose intolerance. The aim of perioperative steroid therapy is to prevent acute adrenal insufficiency and crisis. Elevated midnight serum cortisol level confirms the diagnosis of Cushing’s syndrome with 100% sensitivity.
Anaesthetic of choice include thiopentone followed by suxamethonium, nitrous oxide, halothane because these agents do not cause significant stimulation of adrenocortical function.
(2) Excess mineralocorticoid: sodium retention, potassium depletion, hypertension, hypokalemic alkalosis, these symptoms constitute primary hyperaldosteronism or (Conn’s syndrome) most often the result of a unilateral adenoma. Successful treatment is spironolactone with restoring potassium equilibrium.
(3)Adrenogenital syndrome : excess circulating androgens and is manifested with complaints of hirsutism, acne, and anovulation or infertility. When testosterone is secreted in great excess, women may virilize and exhibit a deepened voice, clitorimegaly, masculinized body habitus, and alopecia. and no spesfic anesthesia for adrenogenital syndrome.
(4) Adrenocortical insufficiency: a patient with primary adrenal insufficiency presenting as (Addison’s disease) usually exhibits hypoaldosteronism present mainly with hypovolaemia and hyperkalemia, if patient is not stressed usually have no perioperative problems, avoid narcotics because they are very sensitive to barbiturates. Induction of anaesthesia by very slow thiopentone. Addison’s crisis may occur postoperative which treated immediately by I.V. hydrocortisone succinate. Mineralocorticoid deficiency: hypoaldosteronism, a much less common either congenital or following unilateral adrenalectomy. Most of patients have low blood pressure, most symptoms due to hyperkalemic acidosis. Treatment with meneralocorticoids (9 fluorocortisone preoperatively) with monitoring.
(5) Pheochromocytoma: catecholamine secreting tumour derived from cliromaffin tissue usually from the adrenal medulla. It is a life-threatening tumour, manifested commonly with palpitation, headaches, and diaphoresis. Diagnosis by measurement of urinary and plasma catecholamine. With preoperative alpha, beta blockers and restoration of blood volume. General anesthesia is preferred than regional anesthesia. Induction is made by intravenous drugs, maintenance with volatile anesthetic ”isoflurane” is of choice, and with muscle relaxant ”vecuronium” is of choice. Continuous infusion of intravenous nitroprusside to control blood pressure intraoperatively. The primary goals of anaesthesia and surgery is to avoid massive sympathetic outflow. Postoperative replacement is usually required as sympathetic tone continue to decrease