The Endocrine System & Hormones Pathways PDF

The Endocrine System hormones pathways Prepared by Dr. Abdulrahman Aljabri Endocrine System Hormones The endocrine system The endocrine system is a Hormones are chemical collection of glands that produce secretions of...

The Endocrine System hormones pathways Prepared by Dr. Abdulrahman Aljabri Endocrine System Hormones The endocrine system The endocrine system is a Hormones are chemical collection of glands that produce secretions of ductless hormones that targeting cells to glands that that travel regulate metabolism, growth and through the bloodstream to development, tissue function, target cells, tissues and sexual function, reproduction, organs. sleep, and mood, among other things..  Characteristics or Properties Functions of Hormones of Hormones Low molecular weight Regulate and maintain homeostasis Small, soluble organic Ensure consistency within cells molecules Control movement of substances in Diffuse quickly but effects are and out of cells (permissive not constant function) Effective in low concentrations Balance and integrate different Travel through the blood body systems (integrative function) Target specific sites different Support fetal development from where they are produced (developmental function)  Endocrine System: Components Components Function Hypothalamus Links the nervous system to the endocrine system via the pituitary gland. Pituitary Gland Often referred to as the "master gland" because it controls other endocrine glands. Thyroid Gland Regulates metabolism, energy generation, and growth. Adrenal Glands Produce hormones like cortisol and adrenaline that help the body respond to stress. Pancreas Produces insulin and glucagon to regulate blood sugar levels. Gonads Ovaries in females and testes in males, produce sex hormones. Pineal Gland Regulates sleep patterns through the release of melatonin The Endocrine System ‫الصورة لإلطالع‬ Types of Hormones based on chemical nature 1. Amino acid 3. Fatty acid 2. Steroids based derived Most hormones Derived from Eicosanoids, belong to this Cholesterol, derived from class, including: gonadal and arachidonic Amines adrenocortical leukotrienes (Tyrosine: dopamine & hormones and epinephrine) prostaglandins Polypeptide hormones (e.g., insulin, growth hormone). Hormone’s classification Based on Hormone Action Group I Hormones Group II Hormones (Water- (Lipophilic Hormones) Soluble Hormones) These hormones are fat- These hormones are water- soluble (lipophilic). soluble. Mostly derived from Bind to receptors on the cell cholesterol. surface. Bind to receptors inside the Trigger the release of cell. molecules inside the cell Examples: Steroid (secondary messengers) to hormones, estrogen, carry out functions. androgens, glucocorticoids, vitamin D (cholecalciferol), thyroxine.  Hormone Action Hormones alter target cell activity by one of the following mechanisms: 1. Ion Channel–Linked Receptors. 2. G Protein–Linked Hormone Receptors. 3. Enzyme-Linked Hormone Receptors. 4. Intracellular Hormone Receptors and Activation of Genes ‫الصورة لإلطالع‬ Hormone Action Hormones circulate to all tissues but only activate cells referred to as target cells. Target cells must have specific receptors to which the hormone binds. Hormone-receptor binding triggers a signal transduction cascade. Hormones can have different effects on different target tissues. E.g. insulin promotes glucose uptake in muscle cells while inhibiting glucose production in the liver. Location of receptors: 1. On the surface of the cell membrane. The membrane receptors are specific mostly for the protein, peptide, and catecholamine hormones. 2. In the cell cytoplasm. The primary receptors for the different steroid hormones. 3. In the cell nucleus. The receptors for the thyroid hormones are found in the nucleus. G Protein–Linked Hormone Receptors Cyclic Adenosine Monophosphate (cAMP) Second Messenger Mechanism A hormone (first messenger) binds to the receptor, which activates a protein inside the cell called a G protein. The G protein then triggers other molecules inside the cell (cAMP second messenger) starting a chain reaction that leads to cellular responses. Such as activating protein kinases. e.g. Adrenaline and Glucagon ‫الصورة لإلطالع‬ Enzyme-Linked Hormone Receptors Example: the Insulin Receptor & Mechanisms of Insulin Action Insulin Receptor Activation: Insulin binds to its receptor, which triggers the tyrosine kinase activity of the receptor, leading to the phosphorylation of specific proteins inside the cell. Insulin’s Effects Insulin increases glucose uptake into cells. ‫الصورة لإلطالع‬  Intracellular Hormone Receptors Example: Steroid (Testosterone &Estrogen) and Thyroid (T3, T4) Hormones Steroid hormones and thyroid hormone diffuse easily into their target cells Once inside, they bind and activate a specific intracellular receptor The hormone-receptor complex travels to the nucleus to regulate gene activity That can influence various functions like growth, metabolism, and reproduction. ‫الصورة لإلطالع‬ Target Cell Activation Target cell activation depends on three factors Blood levels of the hormone Relative number of receptors on the target cell The affinity of those receptors for the hormone Up-regulation – target cells form more receptors in response to the hormone Down-regulation – target cells lose receptors in response to the hormone Major Endocrine Pathways: For example: Thyroid Pathway: Thyrotropin-releasing hormone (TRH) from the hypothalamus triggers thyroid stimulating hormone (TSH) release, stimulating the thyroid to produce T3 and T4, which control metabolism and growth. https://myendoconsult.com/learn/endocrine-feedback- loops/ Feedback Mechanisms: Endocrine pathways typically operate through feedback mechanisms, particularly negative feedback loops, often involving the hypothalamus and pituitary gland, to maintain internal balance (homeostasis). Negative feedback loops, - For instance, high levels of cortisol in the blood will inhibit further release of CRH and ACTH, thereby reducing cortisol Corticotropin-releasing hormone (CRH) production, which helps maintain balance. Adrenocorticotropic hormone (ACTH) https://myendoconsult.com/learn/endocrine-feedback- loops/  Endocrine Dysfunctions Leads to disease states which results from one or more of the followings: 1. Abnormal hormonal production, 2. Hormonal excess (tends to caused severe disease). 3. Production of abnormal hormone ( causes by a gene mutation). 4. Disorder of hormonal receptors. 5. Abnormality of hormonal transport or metabolism.  Hormonal Diseases and Their Causes Disease Cause Diabetes Mellitus Insulin deficiency (Type 1) or insulin resistance (Type 2) Hypothyroidism Deficiency of thyroid hormones (T3 and T4) Hyperthyroidism Overproduction of thyroid hormones (e.g., Graves' disease) Cushing's Syndrome Overproduction of cortisol (often due to steroid use or tumors) Addison's Disease Deficiency of cortisol and aldosterone (adrenal damage) Polycystic Ovary Syndrome (PCOS) Hormonal imbalance, excess androgens Acromegaly/Gigantism Overproduction of growth hormone (GH) Hyperparathyroidism Overproduction of parathyroid hormone (PTH) Hypoparathyroidism Deficiency of parathyroid hormone