Adrenal Gland Lecture Notes PDF

 Adrenal Gland (=Suprarenal gland) Suprarenal glands lie close to the kidneys. Pituitary ACTH stimulate growth of the gland as well as all steps of hormone synthesis. ACTH release is stimulated by stress (i.e., hypoglycemia, hypothermia, shock….. etc). Adrenal cortex is under contro...

 Adrenal Gland (=Suprarenal gland) Suprarenal glands lie close to the kidneys. Pituitary ACTH stimulate growth of the gland as well as all steps of hormone synthesis. ACTH release is stimulated by stress (i.e., hypoglycemia, hypothermia, shock….. etc). Adrenal cortex is under control of pituitary gland ACTH. Adrenal medulla is part of sympathetic nervous system Adrenal gland hormones  Mineralocorticoid Hormones from zona glomerulosa Aldosterone (95%) & Desoxycorticosteron (5%) Aldosterone is the main mineralocorticoid secreted by the adrenal cortex. It acts mainly in the kidney especially on the distal convoluted tubule to increase Na+ absorption in exchange for H+ or K+. It is released in response to : Hyponatremia Hyperkalemia Angiotensin II  Increase in aldosterone secretion is called hyperaldosteronism Clinical picture 1) Hypokalemia 2) Metabolic alkalosis Decrease in aldosterone secretion is called hypoaldosteronism Clinical picture 1) Hyperkalemia 2) Metabolic acidosis  Glucocorticoid Hormones from zona faciculata Cortisol (95%) & corticosterone (5%) Glucocorticoids are essential for life. It exerts its effects on the following organs:  Function of glucocorticoids A. Metabolic effects 1. Carbohydrate metabolism. it has anti insulin effect. It elevates blood sugar level by: ❖ Increasing gluconeogenesis from amino acids. ❖ Decreasing glucose utilization by peripheral tissues. 2. Decrease protein synthesis and increase protein catabolism. 3. Enhance lipolysis and cause fat redistribution. B. Maintenance of normal circulatory functions and maintain cardiovascular responsiveness to catecholamine. C. Hematological effects: 1. It decrease all blood cells except RBC and platelets. 2. It has anti inflammatory effect because it decrease eosinophils, basophils and stabilize their lysosomal membranes.. F. Gastric effects: It increases gastric HCl and decrease mucosal cell proliferation leading to gastritis and peptic ulceration. G. Psychological effects: Euphoria, psychosis, depression, paranoid. H. Increase lung surfactant in late pregnancy. I. Exert aldosterone -like effect. Plasma cortisol level follows a diurnal pattern or circadian rhythm. For those who sleep at night, cortisol levels are highest just before waking and lowest at midnight. Hypercortisolism causes Cushing syndrome Moon face Buffalo hump Pendulous abdomen  Muscle wasting Osteoporosis Poor wound healing Hypocortisolism causes Addison’s disease  Adrenal Medulla Adrenal medulla secretes catecholamine in response to stimulation of sympathetic nervous system during stress. Actions of catecholamine include:- 1. Vasoconstriction & increased blood pressure. 2. Increase heart rate and cardiac output. 3. Bronchodilatation 4. Glycogenolysis. 5. Increase BMR ( calorigenic effect). Tumors of adrenal medulla leads to over secretion of catecholamine. The patient show attacks of hypertension Antidiuretic hormone Functions of ADH : 1. Regulation of body water balance: In the absence of ADH, distal nephron becomes impermeable to water and large volume of diluted urine is excreted (20 ml/ minute ). 2. Stimulation of vascular smooth muscle contraction: This pressor effect occurs with high concentration of ADH secretion. Vasopressor action of ADH is one of the immediate compensatory reactions in hypovolemic shock.  Oxytocin It is synthesized by the hypothalamus as part of a prohormone, then transported down the axons to be stored in secretory granules in nerve terminals in the posterior pituitary. Release of Oxytocin; 1. Nerve signals from stretch receptors of the cervix during parturition. 2. Nerve signals from touch receptors of the nipple during suckling (milk let down reflex). 2. Functions of oxytocin a. Initiation of labor contractile response of uterine muscles to oxytocin is enhanced by estrogen & antagonized by progesterone levels. In late pregnancy, there is increased sensitivity of uterine smooth muscles to circulating levels of oxytocin. b. Milk ejection (milk let down reflex) Suckling by the baby g Stimulation of touch receptors of the nipple g nerve signals in the spinothalamic tract g stimulation of neurons of hypothalamus g secretion of oxytocin g contraction of myoepithelial cells that surround the alveoli of mammary gland  Remember Endocrine glands are ductless glands that secrete regulatory molecules called hormones. Pituitary gland is the master gland of endocrine system. It secretes hormones that regulate function of other endocrine glands ( thyroid stimulating hormone, adrenocorticotrophic hormone & gonadotrophic hormone) as well as growth hormone, prolactin & ADH Thyroyid gland release thyroxine which increase metabolic rate of the body Pancreas secrete:- 1. Insulin which increase body utilization of glucose, thus decreasing blood glucose level. 2. Glucagon which increase blood glucose level by decreasing body glucose utilization Adrenal gland secrete:- 1. Cortisol ( increase blood glucose level) 2. Aldosterone (increase blood sodium). 3. Adrenaline & Noradrenalin (increase heart rate & blood pressure).