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Hormones and Endocrine System
The document summarizes key aspects of the endocrine system and hormone signaling. It describes how hormones are chemical messengers that circulate through the bloodstream and activate target cells. The endocrine system works alongside the nervous system to regulate slower but longer-acting responses, such as reproduction and metabolism. Examples are provided of hormone types, the mechanisms of hormone signaling, feedback loops that regulate hormone levels, and specific endocrine glands like the pituitary, thyroid, and parathyroid glands. Diseases associated with hormonal imbalances like diabetes and hyperthyroidism are also mentioned.
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Hormones and Endocrine System
- 1. Hormones & EndocrineSystem M. Faisal Shahid and Humera Waheed, Ph.D. PCMD, ICCBS. University of Karachi
- 2. Long-Distance Regulators • Bio-chemicalsignals “Secreated” in circulatory system to modulate regulatory messages in the organ system. • Activate specifically on equipped target cells i.e. which have receptor.
- 3. • Two systemscoordination: – a) Endocrine (Ductless) system – b) Nervous system • Endocrine system secretes hormones that coordinate slower but longer-acting responses – E.g. Reproduction & Development, Energy metabolism, growth, and behavior • Nervous system conveys high-speed electrical signals along specialized cells called neurons.
- 4. Classification of SecretedSignaling Molecules – Hormones: Long Range, Slow acting, Long Lasting (E.g. Insulin) – Local regulators: Small Range, Swift acting, Long to Medium Lasting. (E.g. TNFα) – Neurotransmitters: Single Cell Ranged, Highly Focused and Fast Acting (e.g. Acetylcholine) – Neurohormones: Long Range, Highly Specific (ATCH, FSH) – Pheromones: Shed in environment, v. long range, for mating processes. (E.g. Chilogttone)
- 5. The Basics • Endocrinesignals travel via the bloodstream • Endocrine glands are ductless and secrete hormones directly into surrounding fluid
- 6. Signaling Pattern Followed by Hormones Blood vesselResponse Response Response Response (a) Endocrine signaling (b) Paracrine signaling (c) Autocrine signaling (d) Synaptic signaling Neuron Neurosecretory cell Figure 1: Signaling Classification Blood vessel Synapse Response
- 7. Blood vessel Response Response Response (a) Endocrinesignaling (b) Paracrine signaling (c) Autocrine signaling Figure 2: Signaling Classification (Generalized)
- 8. Neurotransmitters • Neurons (nervecells) contact target cells at synapses (Infinitesimally short distances). • Neurotransmitters play a role in sensation, memory, cognition, and movement
- 9. Response (d) Synaptic signaling Neuron Neurosecretory cell Bloodvessel Synapse Response Figure 3: Signaling Classification (Continued)
- 10. • Neurohormones: Hormonesthat originate from neurons of brain and diffuse through the bloodstream
- 11. Pheromones • Pheromones arechemical signals that are released from the body and used to communicate with other individuals in the species • Pheromones mark trails to food sources, warn of predators, and attract potential mates
- 12. Chemical Classes ofHormones • Molecular function of hormones in vertebrates: – Polypeptides (proteins and peptides) – Amines derived from amino acids – Steroid hormones
- 13. • Lipid-soluble: Crosscell membranes ACTS INSIDE CELLS. • Water-soluble hormones: Act extracellularly
- 14. Figure 4: Hormonesaccording to solubilty Water-soluble Lipid-soluble Steroid: Cortisol Polypeptide: Insulin Amine: Epinephrine Amine: Thyroxine
- 15. • The EndocrineResponse: 3 Phases – Reception: Input – Signal transduction: Processing – Response: Output
- 16.
- 17. Figure 5 (b) Signal receptor TARGET CELL Signalreceptor Transport protein Water- soluble hormone Fat-soluble hormone Gene regulation Cytoplasmic response Gene regulation Cytoplasmic response OR (a) NUCLEUS (b)
- 18. Signaling • Binding ofa hormone onreceptor initiates a signal transduction. • It leads to responses in the cytoplasm for either: – Enzyme activation – Change in gene expression
- 19. • The hormoneepinephrine has multiple effects in mediating the body’s response to short-term stress • Epinephrine binds to receptors on the plasma membrane of liver cells • This triggers the release of messenger molecules that activate enzymes and result in the release of glucose into the bloodstream
- 20. Figure 6: EpinephrineCascade cAMP Second messenger Adenylyl cyclase G protein-coupled receptor ATP GTP G protein Epinephrine
- 21. Figure 6 (b):Epinephrine Cascade cAMP Second messenger Adenylyl cyclase G protein-coupled receptor ATP GTP G protein Epinephrine Inhibition of glycogen synthesis Promotion of glycogen breakdown Protein kinase A
- 22. Lipid-Soluble Hormones • Usuallycause gene expression alteration • Steroids, thyroid hormones, and the hormonal form of vitamin D enter target cells and bind to protein receptors in the cytoplasm or nucleus • Protein-receptor complexes then act as transcription factors in the nucleus, regulating transcription of specific genes
- 23. Figure 7. SteroidHormones Signaling Hormone (estradiol) Hormone-receptor complex Plasma membrane Estradiol (estrogen) receptor
- 24. Figure 7 (b):Steroid Hormone Signaling Hormone (estradiol) Hormone-receptor complex Plasma membrane Estradiol (estrogen) receptor DNA Vitellogenin mRNA for vitellogenin
- 25. Multiple Effects ofHormones • The same hormone may have different effects on target cells that have – Different receptors for the hormone – Different signal transduction pathways – Different proteins for carrying out the response • A hormone can also have different effects in different species
- 26. Figure 8. DifferentialEffects of Same Hormone: Epinephrine Glycogen deposits β receptor Vessel dilates. Epinephrine (a) Liver cell Epinephrine β receptor Glycogen breaks down and glucose is released. (b) Skeletal muscle blood vessel Same receptors but different intracellular proteins (not shown)
- 27. Glycogen deposits β receptor Vessel dilates. Epinephrine (a) Livercell Epinephrine β receptor Glycogen breaks down and glucose is released. (b) Skeletal muscle blood vessel Same receptors but different intracellular proteins (not shown) Epinephrine β receptor Different receptors Epinephrine α receptor Vessel constricts. (c) Intestinal blood vessel Figure 8 (b). Differential Effects of Same Hormone: Epinephrine
- 28. Localized Signaling: Paracrine •In paracrine signaling, non-hormonal chemical signals called local regulators elicit responses in nearby target cells • Types of local regulators: – Cytokines and growth factors (Interferon etc.) – Nitric oxide (NO) – Prostaglandins (The PAIN ALARMS)
- 29. Major endocrine glands: Adrenal glands Hypothalamus Pinealgland Pituitary gland Thyroid gland Parathyroid glands Pancreas Kidney Ovaries Testes Organs containing endocrine cells: Thymus Heart Liver Stomach Kidney Small intestine Figure 9. Major Hormone Secretion Sites
- 30. Figure 10. TheFeed-back Loops Pathway Example Stimulus Low pH in duodenum S cells of duodenum secrete secretin ( ) Endocrine cell Blood vessel PancreasTarget cells Response Bicarbonate release Negativefeedback –
- 31. • A negativefeedback loop inhibits a response by reducing the initial stimulus • Negative feedback regulates many hormonal pathways involved in homeostasis
- 32. Insulin and Glucagon:Control of Blood Glucose • Insulin and glucagon are antagonistic hormones that help maintain glucose homeostasis • The pancreas has clusters of endocrine cells called islets of Langerhans with alpha cells that produce glucagon and beta cells that produce insulin
- 33. Figure 11. TheInsulin Loop Homeostasis: Blood glucose level (about 90 mg/100 mL) Insulin Beta cells of pancreas release insulin into the blood. STIMULUS: Blood glucose level rises.
- 34. Figure 12. InsulinLoop Homeostasis: Blood glucose level (about 90 mg/100 mL) Insulin Beta cells of pancreas release insulin into the blood. STIMULUS: Blood glucose level rises. Liver takes up glucose and stores it as glycogen. Blood glucose level declines. Body cells take up more glucose.
- 35. Figure 13. TheInsulin-Glucagon Loop Homeostasis: Blood glucose level (about 90 mg/100 mL) Glucagon STIMULUS: Blood glucose level falls. Alpha cells of pancreas release glucagon.
- 36. Figure 14: TheInsulin Glucagon Loop Homeostasis: Blood glucose level (about 90 mg/100 mL) Glucagon STIMULUS: Blood glucose level falls. Alpha cells of pancreas release glucagon. Liver breaks down glycogen and releases glucose. Blood glucose level rises.
- 37. Target Tissues forInsulin and Glucagon • Insulin reduces blood glucose levels by – Promoting the cellular uptake of glucose – Slowing glycogen breakdown in the liver – Promoting fat storage
- 38. • Glucagon increasesblood glucose levels by – Stimulating conversion of glycogen to glucose in the liver – Stimulating breakdown of fat and protein into glucose
- 39. Diabetes Mellitus • Diabetesmellitus is perhaps the best-known endocrine disorder • It is caused by a deficiency of insulin or a decreased response to insulin in target tissues • It is marked by elevated blood glucose levels
- 40. • Type Idiabetes mellitus (insulin-dependent) is an autoimmune disorder in which the immune system destroys pancreatic beta cells • Type II diabetes mellitus (non-insulin- dependent) involves insulin deficiency or reduced response of target cells due to change in insulin receptors
- 41. Coordination of Endocrineand Nervous Systems in Vertebrates
- 42. • The hypothalamusreceives information from the nervous system and initiates responses through the endocrine system • Attached to the hypothalamus is the pituitary gland composed of the posterior pituitary and anterior pituitary
- 43. • The posteriorpituitary stores and secretes hormones that are made in the hypothalamus • The anterior pituitary makes and releases hormones under regulation of the hypothalamus
- 44.
- 45. Figure 16. TheHormonal Index
- 46. Figure 16 (b).The Hormonal Index
- 47. Figure 16 (c). The Hormonal Index
- 48. Figure 16 (d).The Hormonal Index
- 49. Figure 16(e). TheHormonal Index
- 50. Posterior Pituitary Hormones •The two hormones released from the posterior pituitary act directly on nonendocrine tissues
- 51. Figure 17. ThePosterior Pituitary Hormones Posterior pituitary Anterior pituitary Neurosecretory cells of the hypothalamus Hypothalamus Axon HORMONE OxytocinADH Kidney tubulesTARGET Mammary glands, uterine muscles
- 52. • Oxytocin inducesuterine contractions and the release of milk (positive feedback) • Antidiuretic hormone (ADH) enhances water reabsorption in the kidneys
- 53. Anterior Pituitary Hormones •Hormone production in the anterior pituitary is controlled by releasing and inhibiting hormones from the hypothalamus • For example, the production of thyrotropin releasing hormone (TRH) in the hypothalamus stimulates secretion of the thyroid stimulating hormone (TSH) from the anterior pituitary
- 54. Figure 18. AnteriorPituitary Hormones Hypothalamic releasing and inhibiting hormones Neurosecretory cells of the hypothalamus HORMONE TARGET Posterior pituitary Portal vessels Endocrine cells of the anterior pituitary Pituitary hormones Tropic effects only: FSH LH TSH ACTH Nontropic effects only: Prolactin MSH Nontropic and tropic effects: GH Testes or ovaries Thyroid FSH and LH TSH Adrenal cortex Mammary glands ACTH Prolactin MSH GH Melanocytes Liver, bones, other tissues
- 55. Hormone Cascade Pathways •A primary Hormone Targetting another Hormone Secreting Gland is a TROPIC HORMONE. • Hormone cascade pathways are usually regulated by negative feedback
- 56. Tropic Hormones • Atropic hormone regulates the function of endocrine cells or glands • The four strictly tropic hormones are – Thyroid-stimulating hormone (TSH) – Follicle-stimulating hormone (FSH) – Luteinizing hormone (LH) – Adrenocorticotropic hormone (ACTH)
- 57. Nontropic Hormones • Nontropichormones target nonendocrine tissues • Nontropic hormones produced by the anterior pituitary are – Prolactin (PRL) – Melanocyte-stimulating hormone (MSH)
- 58. • Prolactin stimulateslactation in mammals but has diverse effects in different vertebrates • MSH influences skin pigmentation in some vertebrates and fat metabolism in mammals
- 59. Growth Hormone • Growthhormone (GH) is secreted by the anterior pituitary gland and has tropic and nontropic actions • It promotes growth directly and has diverse metabolic effects • It stimulates production of growth factors • An excess of GH can cause gigantism, while a lack of GH can cause dwarfism
- 60. Thyroid Hormone: Controlof Metabolism and Development • The thyroid gland consists of two lobes on the ventral surface of the trachea • It produces two iodine-containing hormones: triiodothyronine (T3) and thyroxine (T4)
- 61. • Thyroid hormonesstimulate metabolism and influence development and maturation • Hyperthyroidism, excessive secretion of thyroid hormones, causes high body temperature, weight loss, irritability, and high blood pressure • Graves’ disease is a form of hyperthyroidism in humans • Hypothyroidism, low secretion of thyroid hormones, causes weight gain, lethargy, and intolerance to cold
- 62. Normal iodine uptake High level iodine uptake Figure 19:Iodine 131 Uptake Micrograph
- 63. Parathyroid Hormone andVitamin D: Control of Blood Calcium • Two antagonistic hormones regulate the homeostasis of calcium (Ca2+ ) in the blood of mammals – Parathyroid hormone (PTH) is released by the parathyroid glands – Calcitonin is released by the thyroid gland
- 64. Figure 20. ParathyroidLoop PTH Parathyroid gland (behind thyroid) STIMULUS: Falling blood Ca2+ level Homeostasis: Blood Ca2+ level (about 10 mg/100 mL)
- 65. Figure 20 (b).The Parathyroid Loop PTH Parathyroid gland (behind thyroid) STIMULUS: Falling blood Ca2+ level Homeostasis: Blood Ca2+ level (about 10 mg/100 mL) Blood Ca2+ level rises. Stimulates Ca2+ uptake in kidneys Stimulates Ca2+ release from bones Increases Ca2+ uptake in intestines Active vitamin D
- 66. • PTH increasesthe level of blood Ca2+ – It releases Ca2+ from bone and stimulates reabsorption of Ca2+ in the kidneys – It also has an indirect effect, stimulating the kidneys to activate vitamin D, which promotes intestinal uptake of Ca2+ from food • Calcitonin decreases the level of blood Ca2+ – It stimulates Ca2+ deposition in bones and secretion by kidneys Control of Blood Calcium
- 67. Adrenal Hormones: Responseto Stress • The adrenal glands are adjacent to the kidneys • Each adrenal gland actually consists of two glands: the adrenal medulla (inner portion) and adrenal cortex (outer portion)
- 68. Catecholamines from theAdrenal Medulla • The adrenal medulla secretes epinephrine (adrenaline) and norepinephrine (noradrenaline) • These hormones are members of a class of compounds called catecholamines • They are secreted in response to stress- activated impulses from the nervous system • They mediate various fight-or-flight responses
- 69. • Epinephrine andnorepinephrine – Trigger the release of glucose and fatty acids into the blood – Increase oxygen delivery to body cells – Direct blood toward heart, brain, and skeletal muscles, and away from skin, digestive system, and kidneys • The release of epinephrine and norepinephrine occurs in response to nerve signals from the hypothalamus
- 70. Figure 21:The AdrenalHormones Loop Stress Adrenal gland Nerve cell Nerve signals Releasing hormone Hypothalamus Anterior pituitary Blood vessel ACTH Adrenal cortex Spinal cord Adrenal medulla Kidney (a) Short-term stress response (b) Long-term stress response Effects of epinephrine and norepinephrine: 2. Increased blood pressure 3. Increased breathing rate 4. Increased metabolic rate 1. Glycogen broken down to glucose; increased blood glucose 5. Change in blood flow patterns, leading to increased alertness and decreased digestive, excretory, and reproductive system activity Effects of mineralocorticoids: Effects of glucocorticoids: 1. Retention of sodium ions and water by kidneys 2. Increased blood volume and blood pressure 2. Possible suppression of immune system 1. Proteins and fats broken down and converted to glucose, leading to increased blood glucose
- 71. Figure 21 (b):The Adrenal Hormones Loop Stress Adrenal gland Nerve cell Nerve signals Releasing hormone Hypothalamus Anterior pituitary Blood vessel ACTH Adrenal cortex Spinal cord Adrenal medulla Kidney
- 72. Figure 21 (c):The Adrenal Hormones Loop (a) Short-term stress response Effects of epinephrine and norepinephrine: 2. Increased blood pressure 3. Increased breathing rate 4. Increased metabolic rate 1. Glycogen broken down to glucose; increased blood glucose 5. Change in blood flow patterns, leading to increased alertness and decreased digestive, excretory, and reproductive system activity Adrenal gland Adrenal medulla Kidney
- 73. The Corticoids • Theadrenal cortex releases a family of steroids called corticosteroids in response to stress • These hormones are triggered by a hormone cascade pathway via the hypothalamus and anterior pituitary • Humans produce two types of corticosteroids: glucocorticoids and mineralocorticoids
- 74. Figure 22. AdrenalHormones (b) Long-term stress response Effects of mineralocorticoids: Effects of glucocorticoids: 1. Retention of sodium ions and water by kidneys 2. Increased blood volume and blood pressure 2. Possible suppression of immune system 1. Proteins and fats broken down and converted to glucose, leading to increased blood glucose Adrenal gland Kidney Adrenal cortex
- 75. • Glucocorticoids, suchas cortisol, influence glucose metabolism and the immune system • Mineralocorticoids, such as aldosterone, affect salt and water balance • The adrenal cortex also produces small amounts of steroid hormones that function as sex hormones
- 76. Gonadal Gender SpecificHormones • The gonads, testes and ovaries, produce most of the sex hormones: androgens, estrogens, and progestins • All three sex hormones are found in both males and females, but in different amounts
- 77. • Testes: androgens,mainly testosterone, which stimulate development and maintenance of the male reproductive system • Testosterone causes an increase in muscle and bone mass and is often taken as a supplement to cause muscle growth, which carries health risks
- 78. • Estrogens, mostimportantly estradiol, are responsible for maintenance of the female reproductive system and the development of female secondary sex characteristics • In mammals, progestins, which include progesterone, are primarily involved in preparing and maintaining the uterus • Synthesis of the sex hormones is controlled by FSH and LH from the anterior pituitary
- 79. Melatonin and Biorhythms •The pineal gland, located in the brain, secretes melatonin • Light/dark cycles control release of melatonin • Primary functions of melatonin appear to relate to biological rhythms associated with reproduction
- 80. Figure 23. HormonalProcess of Milk Production
- 81. Now, One can: 1.Distinguish between the following pairs of terms: hormones and local regulators, paracrine and autocrine signals 2. Describe the evidence that steroid hormones have intracellular receptors, while water- soluble hormones have cell-surface receptors 3. Explain how the antagonistic hormones insulin and glucagon regulate carbohydrate metabolism 4. Distinguish between type 1 and type 2 diabetes
- 82. 5. Explain howthe hypothalamus and the pituitary glands interact and how they coordinate the endocrine system 6. Explain the role of tropic hormones in coordinating endocrine signaling throughout the body 7. List and describe the functions of hormones released by the following: anterior and posterior pituitary lobes, thyroid glands, parathyroid glands, adrenal medulla, adrenal cortex, gonads, pineal gland
- 83.
- 84.
Editor's Notes
- #7 Figure 45.2 Intercellular communication by secreted molecules
- #8 Figure 45.2 Intercellular communication by secreted molecules
- #10 Figure 45.2 Intercellular communication by secreted molecules
- #15 Figure 45.3 Hormones differ in form and solubility
- #17 Figure 45.5 Receptor location varies with hormone type
- #18 Figure 45.5 Receptor location varies with hormone type
- #21 Figure 45.6 Cell-surface hormone receptors trigger signal transduction
- #22 Figure 45.6 Cell-surface hormone receptors trigger signal transduction
- #24 Figure 45.7 Steroid hormone receptors directly regulate gene expression
- #25 Figure 45.7 Steroid hormone receptors directly regulate gene expression
- #27 Figure 45.8 One hormone, different effects
- #28 Figure 45.8 One hormone, different effects
- #30 Figure 45.10 Major human endocrine glands
- #31 Figure 45.11 A simple endocrine pathway
- #34 Figure 45.12 Maintenance of glucose homeostasis by insulin and glucagon
- #35 Figure 45.12 Maintenance of glucose homeostasis by insulin and glucagon
- #36 Figure 45.12 Maintenance of glucose homeostasis by insulin and glucagon
- #37 Figure 45.12 Maintenance of glucose homeostasis by insulin and glucagon
- #45 Figure 45.14 Endocrine glands in the human brain
- #46 Table 45.1
- #47 Table 45.1
- #48 Table 45.1
- #49 Table 45.1
- #50 Table 45.1
- #52 Figure 45.15 Production and release of posterior pituitary hormones
- #55 Figure 45.17 Production and release of anterior pituitary hormones
- #63 Figure 45.19 Thyroid scan
- #65 Figure 45.20 The roles of parathyroid hormone (PTH) in regulating blood calcium levels in mammals
- #66 Figure 45.20 The roles of parathyroid hormone (PTH) in regulating blood calcium levels in mammals
- #71 Figure 45.21 Stress and the adrenal gland
- #72 Figure 45.21 Stress and the adrenal gland
- #73 Figure 45.21a Stress and the adrenal gland
- #75 Figure 45.21b Stress and the adrenal gland