Adrenal Gland PDF

ADRENAL GLAND Prof. Marwa AbdElaziz  Adrenal Gland COMPOSED OF: *Adrenal Medulla *Adrenal Cortex  ZONES of the Adrenal Cortex 1- Zona Glomerulosa - Outer zone that produces mineralocorticoids (e.g. aldosterone), which are responsible for regulating salt and water metabolism. 2- Z...

ADRENAL GLAND Prof. Marwa AbdElaziz  Adrenal Gland COMPOSED OF: *Adrenal Medulla *Adrenal Cortex  ZONES of the Adrenal Cortex 1- Zona Glomerulosa - Outer zone that produces mineralocorticoids (e.g. aldosterone), which are responsible for regulating salt and water metabolism. 2- Zona Fasciculata -Middle zone synthesizes glucocorticoids (e.g. cortisol), which are involved with normal metabolism and resistance to stress. 3- Zona Reticularis - Inner zone secretes adrenal androgens(e.g. dehydropiandrosterone)  MINERALOCORTICOIDS Aldosterone exerts 90% of mineralocorticoids activity. Functions of aldosterone A- Regulation of electrolytes: the most important function of aldosterone is to increase the reabsorption of sodium and excretion of potassium by the following mechanisms: 1- On the kidney It causes sodium reabsorption and potassium excretion mainly in the collecting tubules and to lesser extent in the distal tubules and collecting ducts.  2- On the intestine Aldosterone increase sodium absorption by the intestine mainly the colon which prevent loss of sodium in stool. 3- On sweat and salivary glands: Aldosterone increase sodium chloride reabsorption and potassium secretion by the gland ducts. B- Regulation of extracellular fluid and arterial blood pressure Sodium reabsorption by the renal tubules stimulate osmotic reabsorption of water. Excess aldosterone causes increase in extracellular fluid volume and arterial blood pressure. Control of Aldosterone Secretion Control of aldosterone secretion: 1- Increased potassium ion concentration in the blood increases aldosterone secretion. 2- Increased activity of the renin-angiotensin system increases aldosterone secretion. Activation of the renin-angiotensin system, usually in response to diminished blood flow to the kidneys, can cause a several fold increase in aldosterone secretion. 3- Decreased sodium ion concentration in the blood increases aldosterone secretion. 4- ACTH: It has a permissive effect on aldosterone secretion.  GLUCOCORTICOIDS Types of glucocorticoids: in humans, cortisol is the dominant glucocorticoids Functions of cortisol 1- On metabolism: a. On carbohydrate metabolism: Increased gluconeogenesis in liver by: - Increase the activity of liver enzymes required to convert amino acids into glucose. -Decrease glucose uptake by tissues (anti insulin effects). b. Effect on protein metabolism: - Extrahepatic tissues: -It increases protein (muscle) catabolism lead to increase amino acids which used in gluconeogenesis. - Decrease protein synthesis. - Hepatic tissue: -Increase amino acid transport into liver cells to be used in gluconeogenesis. Increase conversion of amino acids to glucose. - Increase formation of plasma proteins by the liver cells. c. On fat metabolism: -It increases lipolysis with release of free fatty acids from adipose tissues. -Increases fatty acids oxidation by the cells as a source of energy. 2- Anti-inflammatory effects: - Decreases capillary permeability and edema formation. - Stabilizes lysosomal membrane, so it prevents the release of proteolytic enzymes which stored in lysosomes. 3-Antiallergic effects: prevent histamine release from mast cells as a result of antigen antibody reaction. 4- Anti-stress effects: it increases the resistance of the body to stress. 5- On blood: it increases number of RBCs, neutrophils and platelets but decreases eosinophils and basophils  Control of Cortisol Secretion 1- The hypothalamus secretes CRH which stimulates the anterior pituitary to secretes (ACTH) → stimulates cortisol secretion. Cortisol produces negative feedback inhibition on the hypothalamus and anterior pituitary. 2- Any type of physical or mental stress as trauma can lead within minutes to greatly enhanced secretion of ACTH and consequently cortisol as well. 3- Circadian Rhythm: The secretory rates of CRF, ACTH, and cortisol are high in the early morning but low in the late evening  1- Hyperaldosteronism Primary hyperaldosteronism (Conn's syndrome): Causes: Overproduction of aldosterone results from tumors of the zona glomerulosa. The manifestations: of aldosterone excess include 1- Retention of sodium lead to hypertention results from the expansion of plasma volume, which follows the increased reabsorption of sodium. 2- Loss of potassium (hypokalemia), lead to muscle weakness and cardic arrhythmias. 3- Alkalosis due to H+ loss in urine. 4- Edema not developed because of the escape phenomenon when extracellular fluid volume increases to a certain point the secretion of atrial natriuretic factor increases from the atria results in Na+ excretion inspite of continuous actions of mineralocorticoids on renal tubules.  Cushing Syndrome Causes: Excess cortisol secretion due to: Primary hyperfunction 1- Tumor of the adrenal gland itself. Secondary hyperfunction 1. increased output of ACTH resulting from a pituitary tumor. 2. It may also occur following the over administration of steroid medications.  Manifestations 1) Hypertension caused by excess salt and water retention. 2) Hyperglycemia leads to diabetes. 3) Moon face, bufflo hump and truncal obesity caused by abnormal fat redistribution. 4) Muscle weakness. 5) Osteoporosis. 6) Abdominal skin is streatched by fat deposition also there are thinning of the skin and exposure of the subcutaneous vascular tissue (purple striae). Cushing syndrome  Adrenal Insufficiency Primary adrenal insufficiency (addison's disease): Causes: Failure of the adrenal cortices to produce adrenocortical hormones. It is due to a- Atrophy of the adrenal cortex b- Destruction of adrenal cortex by cancer or autoimmune disease.  Manifestations 1- Lack of aldosterone secretion causes: Sodium levels decrease, while potassium levels rise. Severe dehydration and hypotension. 2- Lack of cortisol secretion causes: - plasma glucose levels drop (hypoglycemia) - decrease resistance to stress. 3-Pigmentation of the skin and mucosal membranes of the mouth is characteristic sign due to excess deposition of melanin Pancreas  Pancreas (mixed gland)  Pancreas is an organ of the digestive system and endocrine system of vertebrates.  It secretes digestive enzymes (Pancreatic Juices) through the pancreatic duct into the digestive tract which break down carbohydrates, proteins, and fats (Exocrine function).  Secrets insulin and glucagon hormones that regulates blood sugar levels (Endocrine function).  Pancreatic Hormones o A small portion of the pancreas, known as Islets of Langerhans is the endocrine portion contains the following cells: 1. Beta Cells: secrete insulin and gastrin. 2. Alpha Cells: secrete glucagon. 3. Delta Cells: secrete somatostatin (it serves to block the secretion of both insulin and glucagon from adjacent cells).  I- Insulin (anabolic hormone)  Insulin is a peptide hormone secreted by the β cells of the pancreatic islets of Langerhans and maintains normal blood glucose levels by facilitating cellular glucose uptake, regulating carbohydrate, lipid and protein metabolism. a. Increases formation of glycogen, fatty acids, and triglycerides in the liver. b. Stimulates glucose uptake by muscle and adipose tissue. It decreases blood glucose concentration. Insulin functions and control of secretion  II- Glucagon  Glucagon is called “fasted state” hormone that works with Insulin to control glucose levels in the blood.  It comes from alpha cells in pancreas.  It increases blood glucose concentration. It stimulates the conversion of stored glycogen (stored in the liver) to glucose, which can be released into the bloodstream. This process is called glycogenolysis. Functions of glucagon and control of secretion The disturbances in pancreatic hormonal secretion Diabetes mellitus  Diabetes mellitus, perhaps is the best-known endocrine disorder.  It is characterized by the inability of the body to produce sufficient amounts of insulin or a decreased response to insulin in target tissues.  It is marked by elevated blood glucose levels.  There are two forms of this disease:  Type 1, or insulin dependent diabetes mellitus (IDDM) Type 1 DM (Juvenile or IDDM): There is absolute deficiency of insulin, due to auto-immune disease in which there is destruction of β-cells. It occur in young age (before the age of 40 years), It treated by Insulin (by subcutaneous injection).  Type 2, or non-insulin dependent diabetes mellitus (NIDDM) which is the most common form of diabetes. It is characterized by decreased tissue sensitivity to insulin. It usually develops after age of 40, and most patients are obese.  Prediabetes  It happens when blood sugar levels are higher than normal. But the blood sugar levels aren't high enough to be called diabetes.  People have prediabetes if their fasting blood glucose level is between 100 mg/dL and 125 mg/dL or if their blood glucose level 2 hours after a glucose tolerance test is between 140 mg/dL and 199 mg/dL.  Prediabetes carries a higher risk of future diabetes  Decreasing body weight by 5 to 10% through diet and exercise can significantly reduce the risk of developing diabetes.  Diagnosis of diabetes mellitus: o Diabetes can be diagnosed if fasting blood glucose levels are 126 mg/dL or higher. o It can be diagnosed if a random (not done after fasting) blood glucose level is higher than 200 mg/dL. o Measurements of hemoglobin A1C can be used to diagnose diabetes.When blood is exposed to high blood glucose levels over a period of time, glucose attaches to the hemoglobin on the surface of red blood cells and forms glycosylated or glycolated hemoglobin (A1C). o People with a hemoglobin A1C level of 6.5% or more have diabetes. If the level is between 5.7 and 6.4, they have prediabetes and are at risk of developing diabetes. o Symptoms: 1- Increase blood glucose (hyperglycemia) more than 135mg% 2- Polyuria, Glucosuria: due to osmotic diuresis from loss of glucose in urine. 3- Polydipsia. 4- Hyperphagia and weight loss. 6- Diabetes increases use of fat for energy: a- Lipolysis of stored fat and release of free fatty acids and increases plasma cholesterol. b-Ketosis: Increase ketone bodies. 7- Getting a lot of infections, such as gum and skin infections.