Types of Hormones PDF

‫بسم هللا الرحمن الرحيم‬ National University, Sudan Faculty of Medicine & surgery Endocrine System Course Types of Hormones Dr. Nazik Eltayeb M. Abdelbasit OBJECTIVES By the end of this lesson the student is expected to know the: 1- Definition & action of hormones 2- Type of...

‫بسم هللا الرحمن الرحيم‬ National University, Sudan Faculty of Medicine & surgery Endocrine System Course Types of Hormones Dr. Nazik Eltayeb M. Abdelbasit OBJECTIVES By the end of this lesson the student is expected to know the: 1- Definition & action of hormones 2- Type of Signals 3- General principles of hormone action 4- Hormone classification 5- Functions & transport of hormones  WHAT ARE HORMONES? Endocrine system: acts through a wide range of chemical messenger called hormones. Hormones are special chemical messenger in the body that created in the endocrine glands. These messengers control most major bodily functions.  WHAT ARE HORMONES? They are natural organic substances, that regulate growth, metabolism and other functions of an organism. They are simply biochemical messengers. They can be classified according to the chemical composition, organs where they work. e.g reproductive hormones in the reproductive organs, and if they either act on the same cell producing them i.e. autocrine or paracrine. 1 Type of Signals 2 3 4 5. Exocrine  WHAT ARE HORMONES? Produced in small amounts by specific tissues (endocrine glands). Secreted into the blood stream. Involved in the transmission of information from one tissue to another and from cell to cell.  Types of hormones are key players in body functions Estrogens Progesterone Testosterone Insulin Cortisol Growth Hormone Adrenaline Thyroid Hormones  GENERAL PRINCIPLES OF HORMONE ACTION Trophic hormone: A hormone that has its primary function the regulation of hormone secretion by another endocrine gland ( examples: FSH,LH,TSH). Synergism: when different hormones work together and have a greater effect than individual hormone action ( examples: prolactin, oxytocin). Permissive: a small amount of one hormone allows a second hormone to have its full effect on a target cell; i.e. first hormone ‘permits’ the full action of the second hormone ( examples: Thyroid hormones required for epinephrine). Antagonism: one hormone produces the opposite effect of the other. The processes involve in both negative and positive feedback ( examples: Insulin & glucagon).  Functions of hormones 1 Maintenance of internal environment - To maintain the body's homeostasis and respond appropriately to changes in the environment, hormone production and secretion must be tightly controlled. - Many bodily functions are regulated not by a single hormone but by several hormones that regulate each other (PTH, aldosterone, calcitriol, calcitonin). Reproduction 2 - A type of hormone involved in puberty, fertility, and sexuality. - Reproductive hormones are usually made in the ovaries (in females) and testes (in males). - The main reproductive hormones estrogen, testosterone, and progesterone.  Functions of hormones 3 Growth and development - The hormones that affect growth in animals are growth hormone, insulin, thyroid hormones, glucocorticoids, prolactin, and gonadal steroids (androgens and estrogens) 4 Production, utilization and storage of energy - These hormones have important roles in energy homeostasis, glucose and lipid metabolism, reproduction, cardiovascular function, and immunity. - They directly influence other organ systems, including the brain, liver, and skeletal muscle, and are significantly regulated by nutritional status (Adrenaline, Insulin, glucagon, cortisol ,and T3 and T4 thyroid hormones)  General classification of Hormones The hormones fall into two general classes based on their solubility. 1. Hydrophilic Hormone: The water soluble hormone. They are transported simply dissolved in blood. Examples: the catecholamines (epinephrine and norepinephrine), Insulin, growth hormone, and prolactin. 1. Lipophilic Hormone: They are poorly soluble in water. They cannot be dissolved in watery blood. They bind to plasma protein and present in the blood in protein bound form. They are lipid soluble. Examples: The lipid soluble hormones include thyroid hormone, steroid hormones and Vitamin D3.  Specific classification of Hormones A. Based on the chemical structure B. Based on the mechanism of action C. Based on the anatomical position  A) Classification based on the chemical nature 1) Protein or peptide hormones Hormones of the hypothalamus and pituitary, Insulin, glucagon, the parathyroid hormone, calcitonin 2) Steroid hormones Adrenocortico-steroid hormones , sex hormones 3) Amino acid derivatives Epinephrine, norepinephrine, T3, T4  B) Based on the mechanism of action Group 1: Hormones that bind to intracellular receptors. Group 2: Hormones that bind to cell surface receptors. a) Second messenger is cAMP eg. ACTH, ADH, PTH, TSH, glucagon b) Second messenger is cGMP eg. ANP, NO c) Second messenger is calcium or phospho-inositol or both eg. ACH. d) Second messenger is a kinase or phosphatase cascade eg. Growth factors , Insulin.  Transport of Hormones After entering the blood hormones either remain in free from or bind with a specific carrier protein. A. Water Soluble Hormones Peptide hormones & biogenic amines readily dissolve in the plasma. So, they do not require special mechanism for their transport. B. Transport of Steroid Hormones Thyroid hormones Thyroxine, steroid hormones & vitamin D are relatively insoluble in plasma & circulate in the bound form. In blood, more than 90% of thyroid & steroid hormones are bound to plasma proteins. The transport proteins are specific for hormones. Generally hormones work in two ways: 1- Synthesis of new protein molecules 2- Changing cell permeability Synthesis of new protein molecules Changing cell permeability Enzyme