Lec (6) Physiology and Pathophysiology of Endocrine System 2 PDF

Academic Year: 2024/2025 Physiology and Pathophysiology ( MD203 ) Lecture No. (6) Endocrine System 2 By Dr/ Mohamed Ahmed Shalaby Department of Pharmacology & Toxicology www.merit.edu.eg ...

Academic Year: 2024/2025 Physiology and Pathophysiology ( MD203 ) Lecture No. (6) Endocrine System 2 By Dr/ Mohamed Ahmed Shalaby Department of Pharmacology & Toxicology www.merit.edu.eg  Academic Year: 2024/2025 Lecture’s Aim Basics of the endocrine system and mechanisms of hormone action. Functions of thyroid, adrenal, pineal, and parathyroid glands. Role of pancreas in blood glucose regulation. Hormonal regulation via feedback mechanisms. Disorders of thyroid, adrenal cortex (Addison’s, Cushing’s), and parathyroid glands. Impacts of hyper/hypoglycemia and diabetes types. Clinical Implications: Metabolic effects of growth hormone and calcium homeostasis. www.merit.edu.eg  Academic Year: 2024/2025 The Thyroid Gland The thyroid gland is located in front of the trachea below the larynx. The hormones produced by the thyroid glands are: 1. Thyroxine (T4) 2. Triiodothyronine (T3) These two hormones are responsible for essential for physical growth, mental development, and maturation of the reproductive system. 3. Calcitonin This hormone is released due to hypercalcemia to reduce the calcium level in blood www.merit.edu.eg  Academic Year: 2024/2025 Iodine is necessary for the synthesis of these hormones. Thyroxine: 4 iodine atoms, less potent, long duration Triiodothyronine: 3 iodine atoms, more potent, short duration The secretion of T4 and T3 is regulated by TSH (thyroid- stimulating hormone) secreted by the pituitary gland, which is stimulated by TRH (thyrotropin-releasing hormone). The levels of T3, and T4 are regulated by a negative feedback mechanism in which increasing levels of T3 and T4 decrease the production and secretion of TSH and TRH. www.merit.edu.eg  Academic Year: 2024/2025 Disorders of Thyroid Hormones 1. Hypothyroidism Myxedema Cretinism * In adults * In infants Swollen eye lids, puffiness of the face, weight Physical and mental retardation gain, cold intolerance and slow heart rate. www.merit.edu.eg  Academic Year: 2024/2025 Disorders of Thyroid Hormones 2. Hyperthyroidism Grave’s Disease The condition is characterized by exophthalmos, weight loss, heat intolerance, tachycardia and excitability of the CNS Goiter Exophthalmos www.merit.edu.eg  Academic Year: 2024/2025 Role of Calcitonin in maintaining Calcium Homeostasis Hypercalcemia (High Ca+2 level) Thyroid Gland Calcitonin Calcitonin stimulates urinary calcium excretion Calcitonin inhibits calcium absorption in the intestines Calcitonin stimulates osteoblasts to deposit calcium in bones www.merit.edu.eg  Academic Year: 2024/2025 Parathyroid Gland Four parathyroid glands: two on the back of each lobe of the thyroid gland The hormone produced by the parathyroid gland is: Parathyroid Hormone (PTH) The secretion of PTH is stimulated by hypocalcemia (Low blood calcium level). PTH increases the calcium level in the blood. Together the calcitonin and PTH maintain the normal calcium level in the blood. www.merit.edu.eg  Academic Year: 2024/2025 Role of PTH in Maintaining Calcium Homeostasis Hypocalcemia (Low Ca+2 level) PTH PTH stimulates calcium reabsorption from the kidneys PTH stimulates calcium absorption in the intestines PTH stimulates osteoclasts to dissolve bones and the release of calcium in the blood www.merit.edu.eg  Academic Year: 2024/2025 Disorders of Parathyroid Hormones Hypoparathyroidism Hyperparathyroidism Low PTH will reduce blood calcium level High PTH will cause low bone density, and causing in muscle cramping, or convulsions. deposition of calcium in body tissues and organs, impairing their functioning. www.merit.edu.eg  Academic Year: 2024/2025 The Endocrine Pancreas The hormone-producing cells of the pancreas are called islets of Langerhans. They contain alpha cells that produce glucagon and beta cells that produce insulin. www.merit.edu.eg  Academic Year: 2024/2025 Hypoglycemia (Low Blood Glucose level) 1. Glucagon: The secretion of glucagon is stimulated by hypoglycemia Glucagon increases the blood glucose level by: Glucagon 1. Glycogenolysis: the breakdown of glycogen into glucose in the liver and muscles 2. Gluconeogenesis: the conversion of amino acids to Glycogen Amino Acids Fats glucose 3. Lipolysis: the breakdown of fats into glycerol which is Glycogenolysis Gluconeogenesis Lipolysis converted to glucose Glucose www.merit.edu.eg  Academic Year: 2024/2025 Hyperglycemia (High Blood Glucose level) 2. Insulin: The secretion of insulin is stimulated by hyperglycemia Insulin decreases the blood glucose level by: 1. Transporting glucose from the blood into the cells Insulin 2. Glycogenesis: and changing glucose into glycogen to be stored in liver and muscles. Glucose Glycogenesis Glycogen www.merit.edu.eg  Academic Year: 2024/2025 Diabetes Type 1 diabetes Type 2 diabetes If the immune system attack and destroy islets of The pancreas makes insulin but the body receptors Langerhans that make insulin. So, the pancreas are not responding to insulin. The body becomes cannot make insulin. resistant to insulin www.merit.edu.eg  Academic Year: 2024/2025 The Adrenal Gland Hormones secreted by the adrenal cortex are: 1. Aldosterone 2. Cortisol Hormones secreted by the adrenal medulla are: Epinephrine and norepinephrine www.merit.edu.eg  Academic Year: 2024/2025 The Adrenal Gland 1. Aldosterone: If the blood pressure is low (hypotension), it will increase the secretion of aldosterone which will cause sodium and water retention and increases blood pressure. www.merit.edu.eg  Academic Year: 2024/2025 2. Cortisol: 1. Increases the use of fats and amino acids for energy but decreases the use of glucose for energy. 2. Anti-inflammatory effect as it blocks the effect of inflammatory mediators N.B: High levels of cortisol will suppress the body immunity and makes the body more susceptible to infections www.merit.edu.eg  Academic Year: 2024/2025 Disorders of Adrenal Cortex Hormones 1. Addison’s disease Caused by decreased levels of cortisol and aldosterone due to atrophy of the adrenal cortex. Symptoms: Hypoglycemia Low blood pressure Weightloss Craving for salty food www.merit.edu.eg  Academic Year: 2024/2025 Disorders of Adrenal Cortex Hormones 2. Cushing Syndrome Caused by increased levels of cortisol and aldosterone due to pituitary gland tumor which secretes high amounts of ACTH. Symptoms: Moon-shaped face Buffalo hump on the back of the neck Rapid weight gain Hair loss www.merit.edu.eg  Academic Year: 2024/2025 The Pineal Gland A small endocrine gland that secrets a hormone known as Melatonin (sleep hormone). The secretion of melatonin depends on the level of light: In the morning: the high light levels stimulates the eyes, a nerve impulse is sent to the pineal gland to reduce the Melatonin secretion and the person feels awake. At night: the low light levels stimulates the pineal gland to increase the Melatonin secretion and the person feels asleep. www.merit.edu.eg  Academic Year: 2024/2025 The Gonads Testis Testosterone: It is important for: 1. Development of male reproductive system 2. Development of secondary male characteristics such as a deepened voice, body hair, and increased muscle mass. www.merit.edu.eg  The Gonads Estrogen: It is important for: Ovaries 1. Development of female reproductive system 2. Development of secondary female characteristics such as increased fats and the development of breast  Academic Year: 2024/2025 Organs with Secondary Endocrine Functions 1. The heart 2. The kidneys The kidneys secret the erythropoietin hormone (EPO) The heart secrets a hormone known as which maintains the red blood cells homeostasis. atrial natriuretic peptide (ANP) that reduce the blood pressure by: 3. The gastrointestinal tract 1. Reducing sodium reabsorption 2. Inhibition of the (RAAS) = Renin The GIT secrets the gastrin Angiotensin Aldosterone System hormone which helps in digestion. www.merit.edu.eg  Academic Year: 2024/2025 Organs with Secondary Endocrine Functions 5. The Liver 4. The thymus gland The liver secrets two important hormones: The thymus gland secrets a hormone known as 1. Insulin-like growth factor (IGF-1) which Thymosin which develop the immune system. stimulates body growth 2. Angiotensinogen which increases blood pressure www.merit.edu.eg Academic Year: 2024/2025 www.merit.edu.eg  Academic Year: 2024/2025 Lecture’s References https://lms.merit.edu.eg/pluginfile.php/34074/mod_resource/content/1/Faculty %20of%20Clinical%20Pharmacy_Physiology%20pathophysiology_003_Recommen ded%20Textbooks_004_ANS%20and%20CNS.pdf www.merit.edu.eg