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Transcript
CHAPTER 12 ENDOCRINE SYSTEM DISORDERS BY Dr.Uche Amaefuna-Obasi (MD) •THERE ARE MORE TO LECTURES THAN JUST POWER POINT SLIDES ENDOCRINE SYSTEM • System of ductless glands • Regulates body functions via hormones secreted into the bloodstream. Human Endocrine Glands Ductless glands transport hormones in the blood Duct glands are exocrine glands that use tubes to carry the secretion (salivary, tears) 2003-2004 ENDOCRINE SYSTEM Major Endocrine Glands: • Hypothalamus • Pituitary Gland •Thyroid Glan • Parathyroid Gland •Thymus •Adrenal Gland ENDOCRINE SYSTEM Other organs containing endocrine tissue: • Pancreas •Kidneys •Heart •Digestive Tract •Placenta •Testes •Ovaries •Pineal Gland HYPOTHALAMUS • ‘Master Gland’ • Function : Control centre • Attached to roof of third ventricle, near thalamus • Continuously receive information on status of body systems via nerve impulses • Monitors composition & temperature of blood • Messages interpreted, evaluated : outgoing messages dispatched via nerves / hormones • Plays role in feedback systems that govern secretions of endocrine system 2. PITUITARY GLAND Pea sized mass of glandular tissue • Lies in sella turcica • Slender stalk: Infundibulum connects pituitary gland to hypothalamus • 2 parts : Neurohypophysis Adenohypophysis Indirectly controls : Growth • Metabolism • Sexual reproduction • Lactation 2. PITUITARY GLAND: PARTS Neurohypophysis Adenohypophysis Small posterior lobe Large anterior lobe Stores hormones Releases hormones Oxytocin Growth hormone (GH) Anti Diuretic hormone (ADH) Thyroid Stimulating hormone (TSH) Adenocorticotropic hormone (ACTH) Lutenizing hormone (LH) Follicle stimulating hormone (FSH) Melanocyte stimulating hormone (MSH) Prolactin (PRL) 2. PITUITARY GLAND: HORMONES Posterior Pituitary Anterior Pituitary HORMONES EFFECTS Oxytocin (OC) Stimulates contraction of uterus & contractile cells of breast ADH Prevents excess urine production GH General body growth ACTH Stimulate adrenal cortex to release hormone TSH Controls thyroid gland LH Stimulates sexual & reproductive function FSH Stimulate production of sperm & egg in ovaries & testis MSH Related to skin pigmentation PRL Initiates milk production in breast Pituitary gland and Hypothalamus serve to link the nervous system other glands and metabolic functions. 2003-2004 Mechanisms of hormone release (a) Humoral: in response to changing levels of ions or nutrients in the blood (b) Neural: stimulation by nerves (c) Hormonal: stimulation received from other hormones 12 Learn the 3 endocrine organs on this slide: Hypothalamus Pituitary (hyophysis) Pineal Hypothalamus__ Anterior pituitary__ (adenohypophysis) _____________Posterior pituitary (neurohypophysis) Hypothalamus___________ Pituitary_________ _ (hypophysis) 13 2003-2004 2003-2004 Endocrine system - together with the nervous system, acts as the body´s communication network - it is composed of various endocrine glands and endocrine cells - the glands are capable of synthetizing and releasing special chemical mesengers - hormones Hormones - substances which are secreted by specialised cells in very low concentrations and they are able to influence secreted cell itself (autocrine influence), adjacent cells (paracrine influence) or remote cells (hormonal influence) Role of endocrine system in vital activity of the organism • The endocrine system is the most important regulatory system. It carries out regulatory influence by means of hormones practically on all functions of an organism – metabolism , growth, reproduction, mental activity, adaptation, functional activity of all organs. • Hormones can be synthesized: а) by epithelial cells (one’s own glandular epithelium ); b) by neuroendocrine cells (hypothalamic cells); c) by myoendocrine cells (muscular fibres of heart atriums). HORMONES • The word hormone is derived from the Greek “hormao” meaning “I excite or arouse” • Hormones communicate this effect by their unique chemical structures recognized by specific receptors on their target cells, by their patterns of secretion and their concentrations in the general or localized circulation The main groups of hormones Classic hormones (produced by specialised glands) are divided into three groups: 1. low molecular (amine) hormones (catecholamines, thyroid hormones, prostaglandins, leucotrienes, dopamine, serotonine, GABA, melatonin ...) 2. steroid hormones (e.g.gluco- and mineralocorticoids) 3. polypeptidic and protein hormones (e.g. insulin, leptin...) Structure and Function • Primary function of the endocrine system – To produce hormones that monitor and coordinate body activities • Endocrine glands secrete hormones directly into the bloodstream • Three hormone categories – Tropic hormones – Sex hormones – Anabolic hormones Glands and their Hormones • Hypothalamus – Structure located above the pituitary gland that translates nervous system impulses into endocrine system messages • Pituitary gland – Produces the hormones that regulate the secretion of other glands • Pineal body – Produces the hormone melatonin Glands and their Hormones (continued) • Thyroid – Produces hormones that regulate body metabolism • Parathyroid – Secretes parathyroid hormone, which affects the amount of calcium in the blood • Thymus – Produces the hormone thymosin that stimulates the lymphoid organs to produce T-lymphocytes or antibodies in newborns and young children 3. THYROID GLAND • Located in middle anterior part of neck: below larynx, in front of trachea • “Butterfly” shape • 2 lobes connected by isthmus • ↑ in size : puberty & pregnancy • Rich blood supply: able to deliver high levels of hormones in short period of time • Produces Thyroxin (T4) & Triiodothyronine (T3) • Calcitonin : involved in calcium & phosphate homeostasis 4. PARATHYROID GLAND • Small rounded mass • Attached to posterior surface of thyroid gland • Produces Parathyroid hormone (PTH) • Controls homeostasis of calcium & phosphate in blood by activating Vitamin D Thyroid and Parathyroid help regulate calcium metabolism Feedback! 5. THYMUS •Plays a role in the immune system •Produces thymosin, thymic humaral factor & thymic factor •Responsible for maturation of Tlymphocytes HARMONES OF THYROID, PARATHYROID & THYMUS ORGAN HORMONE EFFECT Thyroid gland T3 & T4 (Follicular cells) energy utilization oxygen consumption growth & development Thyroid gland (C cells) Calcitonin Calcium ion concentration in body fluids Parathyroid PTH Calcium ion concentration in body fluids Thymus Thymosin Maturation & functional competence of immune system Glands and Their Hormones (continued) • Pancreas – Produces the hormones insulin and glucagon. Insulin regulates transportation of sugar, fatty acids, and amino acids into the cells. • Adrenal glands – Produce about 30 hormones • Gonads – The primary sex glands 6. ADRENAL GLAND • Located superior to the kidney • Divided into: • (i) outer cortex (ii) inner medulla 6. ADRENAL GLAND ADRENAL CORTEX ADRENAL MEDULLA Secretes steroid hormones Secretes hormones controlled by ANS Glucocorticoids (metabolism) eg. cortisol Epinephrine (Adrenaline) Mineralocorticoids (homeostasis of Norepinephrine (Noradrenaline) ions) eg. Aldosterone Gonadocorticoids (oestrogens & androgens) ADRENAL HORMONES REGION Cortex 1. Zona glomerulos 2. Zona fasciculata 3. Zona Reticularis Medulla HARMONES Mineralocortic oid: Aldosterone Glucocorticoid: cortisol EFFECT Renal reabsorption of sodium ions & water. renal potassium ion loss Releases amino acids from skeletal muscle & lipids from adipose. Promotes liver glycogen & glucose formation Androgens Anti inflammatory effect Epinephrine cardiac activity (Adrenaline), blood pressure Norepinephrine glycogen breakdown (Noradrenaline) blood glucose 7. PANCREAS • Flattened organ • Lies retroperitoneally & transversly across posterior abdominal wall • Posterior to stomach, between doudenum on right & spleen on left • Classified as exocrine & endocrine Hormones: • Islets of Langerhans secrete: Glucagon, cells : blood glucose Insulin, cells: blood glucose • Growth harmone inhibiting hormone (GHIH), cells : inhibits glucagon & insulin HORMONES OF PANCREAS CELLS HARMONE EFFECT Alpha () cells Glucagon Glucose synthesis & glycogen breakdown in liver Blood glucose concentration Beta () cells Insulin Stimulation of lipids & glycogen storage & formation Blood glucose concentration Delta () cells Somatostatin Inhibits secretion of insulin & glucagon 12 & 13. TESTES & OVARIES TESTES: • Located within scrotum • Produce testosterone • Stimulates development of male sexual characteristics OVARIES: • Located in pelvic cavity • Produce oestrogen & progesterone • Responsible for development & maintenance of female characteristics & menstrual cycle HORMONES OF REPRODUCTIVE SYSTEM CELLS HORMONES EFFECT Testes Interstitial cells 1. Testosterone 2. Inhibin 1. Maturation of sperm Male secondary sex characteristics 2. Inhibits secretion of FSH Ovaries Follicle cells 1. Oestrogen 2. Inhibin 1. Follicle maturation Female secondary sex characteristic 2. Inhibits secretion of FSH Corpus Luteum Progesterone Prepare uterus for implantation Prepare breast for secretory function OTHER ENDOCRINE TISSUES KIDNEYS: • Renal Erythropoietic factor: erythropoietin HEART: • Atrial Natriuretic factor (ANF) GIT: • Stomach gastrin, enteric gastrin, secretin, cholecystokinin, enterocinin, gastric inhibiting hormone PLACENTA: • Human chorionic gonadotropin, oestrogen, progesterone, relaxin Glands and Their Hormones (continued) • Prostaglandins – Known to decrease blood pressure, cause fever, increase hydrochloric acid secretion in the stomach, increase uterine contraction during pregnancy, and influence intestinal peristalsis PROSTAGLANDINS • Regulators of cell metabolism Important in normal physiology of: Pathology: Induce Inflammation • Smooth muscle • Promote fever • Blood flow • Intensify pain • Platelet function • Nerve transmission • Immune response • Secretion • Reproduction • Respiration • Fat Metabolism FEEDBACK CONTROL OF HORMONE RELEASE • Regulation Eg. Production of releasing substance / inhibiting substance Release of hormone from pituitary gland stimulates hormone release by target gland hormone exert normal effect & influence further release of a releasing or inhibiting substance inhibit release of hormone from pituitary gland STARTER answers Pituitary gland – FSH, LH (stimulates the release and maturity of follicles during menstruation) Thyroid gland – Thyroxine (regulates the rate of metabolism) Adrenal gland - corticosteroids and catecholamines including cortisol and adrenaline and small amounts of testosterone (regulates stress levels) Pancreas – peptides (regulates the production of shorter active digestive enzymes) Ovary – oestrogen, progesterone and small amounts of testosterone (regulates the growth of eggs and stabilises the growing foetus during pregnancy) Testis – testosterone (plays a key role in the health and well-being of the man) Hormonal Changes of Puberty • Adrenal gland secretes the hormones that begin the development of secondary sexual characteristics • In a man, the voice deepens and facial hair begins to grow • In a woman, the breasts enlarge and fatty tissue is deposited around the hips • In both men and women height and weight increase Hormonal Changes of Pregnancy • The placenta, or interfacing organ between the fetal and maternal circulation, produces a hormone called human chorionic gonadotropin (hCG) • Increased estrogen and progesterone from the ovaries are maintained until the placenta begins to produce these hormones • Progesterone increases the mobility of the pelvic and lower back bones to allow the birthing process • The pituitary and thyroid glands increase in size, resulting in a higher metabolic rate Hormonal Changes of Menopause • Menopause occurs following a decrease in secretion of the gonadotropins folliclestimulating hormone (FSH) and luteinizing hormone (LH) • A decrease in the secretion of the hormone estrogen by the ovaries occurs • Hot flashes, periods of feeling extreme heat, are the only universal symptom of menopause Assessment Techniques • • • • • Basal metabolic rate (BMR) Protein-bound iodine (PBI) Immunoassay Radioiodine uptake (RAIU) studies Glucose tolerance testing (GTT) CHALLENGES WITH THE ENDOCRINE SYSTEM • Too much or too little of any hormone can be harmful to the body • If the pituitary gland produces too much growth hormone, a child may grow excessively tall • If it produces too little, a child may be abnormally short Etiology of endocrine disorders Reasons of disorders: mental trauma, necrosis, tumor, inflamatory process, bacterial and viral infections, intoxications, local disorders of blood circulation (hemorrhage, thrombosis), alimentary disorders (deficiency of iodine and cobalt in food and drinking water, redundant consumption of carbohydrates), ionising radiation, inherent chromosome and gene defects. Types of endocrine disorders • 1. Hyperfunction of endocrine glands • 2. Hypofunction of endocrine glands • 3. Dysfunction of endocrine glands Endocrine disorders can result from dysfunction originating in the peripheral endocrine gland itself (primary disorders) or from under stimulation or overstimulation by the pituitary (secondary disorders). The disorders can result in hormone overproduction (hyperfunction) or underproduction (hypofunction).. Pathogenesis of endocrine disorders • 1. Disorders of endocrine glands regulation – deregulatory disorders; • 2. Disorders of hormones biosynthesis and their secretion – glandular disorders; • 3. Disorders of the transport, reception and metabolism of hormones – peripheral disorders. THYROIDAL DYSFUNCTION AND ENVIRONMENTAL CHEMICALS Thyroid hormones are essential for normal brain development during a critical period beginning in utero and extending through the first 2 years postpartum Thyroid Gland Hormone: Thyroxin Overactivity (Too much hormone) - Increased metabolic rate - Increased food intake but loss of weight - Hyperthyroidism (Grave’s disease) - Goitre (swollen neck, maybe bulging eyes) Goitre Thyroid Gland Hormone: Thyroxin Underactivity (Not enough hormone) - Hypothyroidism (Hashimoto’s disease) Reduced metabolic rate Low food intake but gain of weight Myxoedema (when onset in adults) Cretinism (when onset in children) Can also cause a goitre Myxoedema • • • • • • Puffiness (swelling) Fatigue Obesity Dry, thickened skin Mental impairment Thin, brittle hair Cretinism • • • • Protuberant abdomen Short Stature Infertility Neurological impairment • Constant Fatigue • Obesity ENDEMIC CRETINISM ENVIRONMENTAL DISEASE Children with endemic cretinism suffer from hypothyroidism that begins at conception because the dietary iodine deficiency prevents synthesis of normal levels of thyroid hormones Symptoms include : • Mental retardation that can be profound • Spastic diplegia: historically known as Little's Disease, is a form of cerebral palsy (CP) that is a chronic neuromuscular condition of hypertonia and spasticity manifested as an especially high & constant "tightness" or "stiffness" in the muscles of the lower extremities of the human body, usually those of the legs, hips & pelvis. • Problems with gross and fine motor control resulting from damage to both the pyramidal and the extrapyramidal systems Thyroid Gland Hormone: Calcitonin Overactivity - Increased Bone Ca, decreased Blood Ca - Tetany (nerve problems leading to muscle spasms or cramps) Underactivity - Increase Blood Ca, decreased Bone Ca - Osteoporosis (brittle bones) - Kidney stones HYPERTHYROIDISM • Hyperthyroidism is a condition in which the levels of thyroid hormones in the blood are excessively high • Symptoms may include: weight loss, nervousness, tremors, excessive sweating, increased heart rate and blood pressure, protruding eyes, and a swelling in the neck from an enlarged thyroid gland (goiter) HYPOTHYROIDISM • Hypothyroidism is a condition in which levels of thyroid hormones in the blood are abnormally low. Thyroid hormone deficiency slows body processes • Symptoms may include fatigue, slow heart rate, dry skin • In children: slower growth and delayed puberty • Hashimoto's thyroiditis, which results from an autoimmune process that damages the thyroid and blocks thyroid hormone production, is the most common cause of hypothyroidism in kids Parathyroid Glands Hormone: Parathormone (PTH) Underactivity - Low Blood calcium, High Bone Ca - Tetany Overactivity - High Blood calcium, Low Bone Ca - Osteoporosis Calcitonin Vs. Parathormone Calcitonin – Over Reactivity Under Reactivity Blood Ca Parathormone - Blood Ca Tetany Blood Ca •Osteoporosis •Kidney Stones Blood Ca •Osteoporosis •Kidney Stones Blood Ca Tetany Blood Ca Pancreas Hormone: Insulin Overactivity - Low blood sugar level ( ↓BSL) - Hypoglycemia Underactivity - High blood sugar level ( ↑BSL) - Hyperglycemia - Diabetes Pancreas Hormone: Glucagon Overactivity - High blood sugar level ( ↑BSL) - Diabetes Underactivity - Low blood sugar level ( ↓BSL) - Hyper insulinism Insulin vs Glucagon Insulin – Over Reactivity Under Reactivity BSL BSL Hypoglycemia BSL •Hyperglycemia •Diabetes Glucagon - BSL BSL •Hyperglycemia •Diabetes BSL Hypoglycemia Anterior Pituitary Gland Hormone: Growth Hormone Overactive - Gigantism (children - very tall) - Acromegaly (adults - bones & skin thicken) Underactive - Dwarfism (very short) Gigantism The man holding the baby in the photo is 8 ft, 2.5 inches tall Acromegaly Dwarfism Dwarfism occurs when there is short supply of GH in childhood. There are two types of dwarfism – Lorrain and Frohlich’s Disorders of the Endocrine System • Acromegaly – An enlargement of the bones of the hands, feet, and jaws • Addison's disease – Caused by hyposecretion of the hormones produced by the cortex of the adrenal gland • Cretinism – Condition resulting from a congenital deficiency of thyroid secretion or hypothyroidism Disorders of the Endocrine System (continued) • Cushing’s syndrome – Disorder that causes hyperactivity of the adrenal glands, which is triggered by the oversecretion of the pituitary hormone ACTH • Diabetes insipidus – From an acquired or inherited decrease in the antidiuretic hormone secreted by the pituitary • Diabetes mellitus – A disorder of carbohydrate, fat, and protein metabolism resulting from insufficient insulin production by the pancreas DIABETES • Group of diseases marked by high levels of blood glucose resulting from defects in insulin production, insulin action, or both • Diabetes can lead to serious complications and premature death • More than 220 million people worldwide have diabetes • More than 80% of diabetes deaths occur in low- and middleincome countries TYPE 1 DIABETES • Previously called insulin-dependent diabetes mellitus (IDDM) or juvenile-onset diabetes • Type 1 diabetes develops when the body's immune system destroys pancreatic beta cells. This form of diabetes usually affects children and young adults • Risk factors for type 1 diabetes may be autoimmune, genetic or environmental CHEMICALS AND TYPE 1 DIABETES • Chemicals or drugs can be environmental triggers to diabetes • Some that have been considered include: – – – • the chemical Alloxan the rodenticide Vacor and the drugs Streptozotocin and Pentamidine All of these may cause an immune system response that could result in the destruction of insulin-producing cells TYPE 2 DIABETES • Previously called non–insulin-dependent diabetes mellitus (NIDDM) or adult onset diabetes • Type 2 diabetes comprises 90% of people with diabetes around the world, and is largely the result of excess body weight and physical inactivity. • Symptoms may be similar to those of Type 1 diabetes, but are often less marked. As a result, the disease may be diagnosed several years after onset, once complications have already arisen. • Until recently, this type of diabetes was seen only in adults but it is now also occurring in children Rising prevalence of this type of diabetes in children has paralleled the dramatically increasing rates of obesity among children Disorders of the Endocrine System (continued) • Dwarfism – Results from hyposecretion of the growth hormone of the pituitary gland, which has been caused by a tumor, infection, genetic factors, or trauma • Gigantism – An excessive growth of the long bones caused by hypersecretion of the somatotropic hormone • Graves’ disease – Caused by hyperthyroidism or thyrotoxicosis Disorders of the Endocrine System (continued) • Hyperparathyroidism – Causes hypercalcemia, an increased calcium blood level • Hypoglycemia – Results from increased insulin production by the pancreas • Hypoparathyroidism – A decreased secretion of parathyroid hormone that causes tetany Disorders of the Endocrine System (continued) • Hypothyroidism – Also called Hashimoto's disease, results from an insufficient production of thyroxine • Syndrome of inappropriate antidiuretic hormone (SIAD) – Involves water intoxication and the dilution of intracellular and extracellular body tissues, usually resulting from lung cancer • Virilism – Results from increased secretion in the adrenal glands THE EPIDEMIC OF OBESITY IN CHILDREN AND ADOLESCENTS • Prevalence of obesity has reached alarming levels • It affects both industrialized and developing countries of all socioeconomic groups, irrespective of age, sex or ethnicity WHO Nearly 43 million children under the age of five were overweight in 2010 (WHO) OBESITY: CONTRIBUTING FACTORS • Genetic • Behavioural • Environment Home, child care, school and community environments can influence children's behaviors related to food intake and physical activity WHO WHY IS CHILDHOOD OBESITY CONSIDERED A HEALTH PROBLEM? • Heart disease, caused by: – high cholesterol and/or – high blood pressure • Type 2 diabetes • Asthma • Sleep apnea • Social discrimination PREVENTION: HOW TO MAINTAIN A HEALTHY WEIGHT ? Policy and environmental change initiatives that make healthy choices in nutrition and physical activity available, affordable, and easy will likely prove most effective in combating obesity Balancing calories Help children develop healthy eating habits Help children eat organic food Help children stay active and reduce sedentary time Issues and Innovations • Steroid abuse – Causes problems for men such as stunted growth, liver tumors, and decreased sperm production – Causes problems for women such as loss of menstrual cycle and baldness PRECOCIOUS PUBERTY • Puberty is the process of physical maturation manifested by an increase in growth rate and the appearance of secondary sexual characteristics • Precocious puberty has most commonly been defined as the onset of puberty (appearance of any sign of secondary sexual maturation) before the age of 8 yr in girls and before the age of 9 yr in boys. • It involves early physical changes of puberty & also linear growth acceleration and acceleration of bone maturation, which leads to early epiphyseal fusion and short adult height. PRECOCIOUS PUBERTY & ENVIRONMENTAL EXPOSURES Mycotoxins - mycoestrogen Zearalenone produced by the fungus Fusarium spp. suspected to be a triggering factor for precocious puberty development in girls • DDT (dichloro diphenyl trichloroethane), DDE (Dichlorodiphenyl dichloroethylene), PCBs (polybrominated bipheny), and phthalates have been associated with early puberty • Drug exposure: compounds with estrogenic activity may be present in some drugs like oral contraceptives HYPOSPADIAS One of the most common birth defects Incidence: 1 in 250 newborn males; the number has doubled in the last 3 decades (Paulozzi,1997) Etiology: remains unknown but there is a correlation with maternal environmental exposure and endocrine disruptors Hypospadias can be defined as an anatomical defect in the formation of the urethra on the ventral aspect of the penis, an arrest in the development of the normal circumferential prepuce, and varying degrees of penile curvature. A working hypothesis to explain the etiology of hypospadias as well as the increase in hypospadias is maternal environmental exposure or endocrine disruptors. MATERNAL & PATERNAL RISK FACTORS FOR CRYPTORCHIDISM AND HYPOSPADIAS • • • • Paternal pesticide exposure - cryptorchidism Paternal smoking - hypospadias Small gestational age - hypospadias Preterm birth - cryptorchidism DIETHYLSTILBESTROL (DES) AND CRYPTORCHIDISM • Prenatal exposure to DES (Diethylstilbestrol), a synthetic estrogen, increases risk of male urogenital abnormalities and the association is strongest for exposure that occurs early in gestation • Study findings support the hypothesis that endocrine disrupting chemicals may be a cause of the increased prevalence of cryptorchidism that has been seen in recent years MSH - Melanocyte Stimulating Hormone – causes color cells (melanocytes) in skin to darken Overactive • Skin darkens Under active • Skin will not darken • Most severe condition is albinism LH, FSH, ICTH – sex hormones in males and females that aid in sperm or egg (gamete) production Overactive • Unknown Underactive • Sterility Corticoids – inc. blood pressure, inc. food metabolism and dec. inflammation Overactive • Cushing’s Syndrome Underactive • Addison’s Disease • Decreased cortisol and/or aldosterone production