dr.may lecture 15


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Endocrinology 2013 - ah

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dr.may lecture 15

  1. 1. Dr. Maie Al-Bader - Endocrinology 2013 1ENDOCRINOLOGYDr Maie Al-BaderDept. of PhysiologyExt: 6355E-mail: albader@hsc.edu.kw
  2. 2. Dr. Maie Al-Bader - Endocrinology 2013 2 ENDOCRINOLOGY• The main function of the endocrine system is to maintain the homeostasis of the internal environment• Hormone: chemical messengers secreted by cells of endocrine glands (ductless glands) and tissues that regulate the activity of other cells in the body.
  3. 3. Dr. Maie Al-Bader - Endocrinology 2013 3Endocrine Glands that FunctionPrimarily to Secrete Hormones1. Pituitary gland: ADH (vasopressin), oxytocin & trophic hormones2. Thyroid gland: thyroxine, tri-iodothyronine & calcitonin3. Parathyroid gland: parathyroid hormone4. Adrenal gland: cortisol, aldosterone, epinephrine & sex steroids5. Pancreas: insulin and glucagon6. Ovaries & testicles: androgens, estrogens & progesterone7. Pineal gland: melatonin8. Thymus gland: thymosine
  4. 4. Dr. Maie Al-Bader - Endocrinology 2013 4Other Organs which FunctionSecondarily as Endocrine Glands1. Heart: atrial natriuretic peptide (ANP)2. Kidney: erythropoietin3. Liver: somatomedin (IGF)4. Skin: vitamin D35. Gastrointestinal tract: gastrin, CCK and VIP6. Adipose tissue: leptin7. Hypothalamus: releasing and inhibiting hormones
  5. 5. Dr. Maie Al-Bader - Endocrinology 2013 5Mechanism of Hormone ActionFunctional categories of hormones based on the location of theirreceptor proteins and mechanisms of action: a. Hormones that bind to nuclear receptor proteins e.g. steroid and thyroid hormones (what would be the characteristics of such hormones?) b. Hormones that use second messengers e.g. protein and peptide hormones (what would be the characteristics of such hormones?)
  6. 6. Dr. Maie Al-Bader - Endocrinology 2013 6 Hormones that Bind to Nuclear Receptor ProteinsSteroids Lipohilic steroid hormones are bound to carrier proteins in plasma. They then dissociate from these proteins in order to pass through the lipid component of the target cell membrane and enter target cell where their receptor proteins are located  Secreted by: adrenal cortex, testes and ovaries  Location of receptors: in cytoplasm or nucleus of the target cell
  7. 7. Dr. Maie Al-Bader - Endocrinology 2013 7Thyroid HormonesVery similar to steroids in size; being non-polar; and very water-insoluble; carriedmainly by thyroxine-binding globulin (TBG; T4 more than T3) Secreted by: thyroid gland Location of receptor proteins: are in the nucleus of target cells
  8. 8. Dr. Maie Al-Bader - Endocrinology 2013 8Hormones that Use SecondMessengers Catecholamines (epinephrine and norepinephrine), polypeptides and glycoproteins cannot pass the lipid bilayer of the cell membrane and thus mediate their effects through second messengers  Secreted by: all glands EXCEPT adrenal cortex, gonads and thyroid  Location of receptors: outer surface of the membrane  Effects of hormone-receptor interaction: stimulates production of intracellular second messenger including c-AMP, c-GMP, phospholipase C, Ca2+ and tyrosine kinase
  9. 9. Dr. Maie Al-Bader - Endocrinology 2013 9 Pituitary Gland (Hypophysis) The pituitary gland is divided into two lobes:1. Anterior hypophysis (adenohypophysis)2. Posterior pituitary or neurohypophysis (neural part of the pituitary; pars nervosa)
  10. 10. Dr. Maie Al-Bader - Endocrinology 2013 10 Posterior Pituitary HormonesPosterior pituitary secretes only two hormones which are: Produced by the hypothalamus Stored in the posterior pituitary
  11. 11. Dr. Maie Al-Bader - Endocrinology 2013 11Antidiuretic hormone (ADH)• Also known as arginine vasopressin (AVP)• It stimulates retention of water by the kidneysOxytocinIn females:• It stimulates the contraction of the uterus during labour (required for parturition; childbirth)• It stimulates milk-ejection reflex in a lactating woman, i.e., contractions of the mammary gland alveoli and ducts
  12. 12. Dr. Maie Al-Bader - Endocrinology 2013 12Control of ADH & Oxytocin Secretion by Neuro-Endocrine Reflex
  13. 13. Dr. Maie Al-Bader - Endocrinology 2013 13 Anterior Pituitary Hormones Secreted by pars distalis of adenohypophysisThey include:  Thyroid-stimulating hormone (TSH)  Adrenocorticotropic hormone (ACTH)  Follicle-stimulating hormone (FSH)  Luteinizing hormone (LH)  Prolactin  Growth hormone (GH) or somatotropin
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  15. 15. Dr. Maie Al-Bader - Endocrinology 2013 15Hyposecretion of growth hormone: During childhood  pituitary dwarfism (with normal body proportions) During adulthood  Simmonds’ diseaseHypersecretion of growth hormone: During childhood  gigantism During adulthood  acromegaly (no further growth BUT person’s appearance changes as a result of thickening of bones, growth of soft tissues as in face, hands and feet)
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  18. 18. Dr. Maie Al-Bader - Endocrinology 2013 18Control of Secretion ofAnterior Pituitary Hormones1. Hypothalamic control: achieved through hormonal control2. Feedback control by hormones secreted from target gland
  19. 19. Dr. Maie Al-Bader - Endocrinology 2013 191. Hypothalamic Control DOPAMINEGHRH TRH (PIH) GnRH CRH HYPOTHALAMUS ANTERIORGH TSH PRL LH & FSH ACTH PITUITARYCRH: Corticotropin-releasing hormoneGnRH : Gonadotropin-releasing hormoneTRH: Thyrotropin-releasing hormonePIH or dopamine: Prolactin-inhibiting hormoneGHRH: Growth hormone-releasing hormone STIMULATE INHIBIT
  20. 20. Dr. Maie Al-Bader - Endocrinology 2013 202. Feedback Control Of Anterior Pituitary Secretion of ACTH, FSH, LH and TSH is controlled by negative feedback inhibition: •Target gland hormones  hypothalamus •Target gland hormones  anterior pituitary •Anterior pituitary  hypothalamus
  21. 21. Dr. Maie Al-Bader - Endocrinology 2013 21 Adrenal Glands Each adrenal gland consists of adrenal cortex and adrenal medulla• The adrenal medulla cells secrete catecholamines (epinephrine and norepinephrine; 4:1 ratio) and are innervated by sympathetic nerve fibers; activated by stress• Once simulated the actions are • very similar to those caused by stimulation of sympathetic nervous system, however, they last ten times longer • Activation of both the adrenal medulla and the sympathetic nervous system  prepares the body for greater physical performance (fight-or-flight)
  22. 22. Dr. Maie Al-Bader - Endocrinology 2013 22
  23. 23. Dr. Maie Al-Bader - Endocrinology 2013 23 Adrenal CortexSecretes steroid hormones called corticosteroids (corticoids) includingmineralocorticoids, glucocorticoids and sex steroids
  24. 24. Dr. Maie Al-Bader - Endocrinology 2013 24Mineralocorticoids (Aldosterone):• Zona glomerulosa • Secretes aldosterone which acts on the kidneys to regulate Na+ and K+ balanceGlucocorticoids (Cortisol):• ACTH stimulates the zona fasiculata (little in zona reticularis) to secrete cortisol.• Cortisol is a catabolic hormone that acts on the liver, muscle & adipose tissues (to regulate carbohydrate, protein and fat metabolism) leading to an: •  serum glucose •  serum free fatty acid •  serum amino acidSex steroids:• Weak androgens secreted by zona reticularis of adrenal cortex• Supplement of sex steroids secreted by the gonads
  25. 25. Dr. Maie Al-Bader - Endocrinology 2013 25 Adrenal Cortex Secretion Abnormalities1. Cushings syndrome/disease: Cause: hypersecretion of corticosteroids as a result of:  tumor of adrenal cortex (Cushing’s syndrome)  oversecretion of ACTH from anterior pituitary (Cushing’s disease)  (what are the two main differences between the syndrome and disease?) Characterized by:  hyperglycemia  hypertension  muscular weakness  structural changes: moon face, purple abdominal striae, truncal obesity, buffalo hump and spindly arms and feet
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  28. 28. Dr. Maie Al-Bader - Endocrinology 2013 282. Addison’s disease: Cause: inadequate secretion of cortisol and aldosterone Characterized by:  hypoglycemia  Na+ loss and K+ retention  dehydration  hypotension  rapid weight loss  generalized weakness  May lead to death if not treated with corticosteroids
  29. 29. Dr. Maie Al-Bader - Endocrinology 2013 293. Adrenogenital syndrome:Cause: hypersecretion of adrenal sex hormones, particularly androgens • In young children  premature puberty and enlarged genitals • In mature women  growth of beard
  30. 30. Dr. Maie Al-Bader - Endocrinology 2013 30Thyroid Glands• Secretes • thyroxine (T4) • triiodothryonine (T3) • calcitonin
  31. 31. Dr. Maie Al-Bader - Endocrinology 2013 31 Production and Storage of Thyroid HormonesTarget organ: almost all body organs• Actions: • stimulates protein synthesis • promotes proper skeleton growth and development • promotes maturation of the CNS • its level in the blood determines the BMR (the minimum rate of caloric expenditure by the body)
  32. 32. Dr. Maie Al-Bader - Endocrinology 2013 32 Hypothyroidism1. Iodine-deficiency (endemic goitre): form of hypothyroidism, caused by the lack of adequate iodine in the diet2. Cretinism: newborn infants born in areas of low iodide intake and endemic goitre. Symptoms include : mental retardation, short stature, puffy face and hands, deaf mutism etc.
  33. 33. Dr. Maie Al-Bader - Endocrinology 2013 333. Infantile hypothyroidism: occurs during childhood. Symptoms include: retarded growth, abnormal bone development, low IQ, general lethargy and low body temp4. Hashimoto thyroiditis: form of hypothyroidism, characterized by a goitre, high concentrations of antibodies, which are directed against thyroglobulin and thyroid peroxidase. The progressive destruction of thyroid follicular tissue results in hypothyroidism5. Myxoedema: hypothyroidism in adulthood. Symptoms include: edema, low basal metabolic rate, low body temperature, cold intolerance, lethargy and weight gain tendency
  34. 34. Dr. Maie Al-Bader - Endocrinology 2013 34Hyperthyroidism Graves’ Disease(Toxic Goitre)• It is an autoimmune disease caused by antibodies that act like TSH causing the growth of the thyroid associated with hypersecretion of thyroxine• Clinical symptoms include: • BMR •  heart rate • weight loss • excessive sweating • heat intolerance • exophthalamus (bulging of the eyes; because of edema in tissues of eye socket)
  35. 35. Dr. Maie Al-Bader - Endocrinology 2013 35Regulation of Calcium and PhosphateCa2+ and phosphate concentration in plasma is affected by: • Bone resorption and absorption • Intestinal absorption • Urinary excretionRegulation of plasma calcium and phosphate BY: • Parathyroid hormone • Calcitonin • Calcitriol (1,25-dihydroxyvitamin D3)
  36. 36. Dr. Maie Al-Bader - Endocrinology 2013 36Parathyroid Hormone (PTH)• PTH is secreted by the parathyroid glands (usually 4) whenever the plasma concentration of Ca2+ begins to fall• PTH promotes a rise in blood calcium levels by acting on: • Bones: stimulating bone resorption • Kidneys: reabsorbtion of Ca2+ from glomerular filtrate and inhibiting reabsorption of phosphate • Intestine (indirect) : promoting the formation of 1,25-dihydroxyvitamin D3 by stimulating 1a-hydroxylase in the kidney
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  38. 38. Dr. Maie Al-Bader - Endocrinology 2013 38 Calcitriol (1,25-dihydroxyvitamin D3)• Production starts in the skin where Vitamin D3 is produced from precursor molecule 7- dehydrocholesterol under the influence of sunlight• Actions: • Activity stimulated by PTH • Helps to raise plasma concentration of calcium and phosphate by stimulating: • Intestinal absorption of calcium and phosphate (main function) • Resorption of bones • Renal reabsorption of calcium and phosphate
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  40. 40. Dr. Maie Al-Bader - Endocrinology 2013 40 Calcitonin• Calcium lowering hormone• Secreted by the parafollicular cell in the thyroid gland• It antagonizes the hypercalcemic effect of calcitriol and PTH• Is stimulated by high plasma Ca2+ and phosphate levels and acts to lower Ca2+ levels by: • inhibiting bone resorption • stimulating the urinary excretion of Ca2+ and phosphate by inhibiting their reabsorption by the kidneys
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  42. 42. Dr. Maie Al-Bader - Endocrinology 2013 42 Osteoporosis• Osteoporosis is characterized by low bone mass (due to the reduced deposition of collagen as well as mineral). It occurs when bone resorption exceeds formation• The bones become fragile & susceptible to fracturing (mainly hip, spine and wrist)• Weight-bearing exercise builds denser, stronger bones (age 25 to 30). Weight- lifting, jogging, hiking, stair-climbing, step aerobics, dancing, racquet sports, and other activities that require your muscles to work against gravity.
  43. 43. Dr. Maie Al-Bader - Endocrinology 2013 43 PancreasThe pancreas consists of an endocrine and an exocrine portion. The exocrine portion is important for production of both bicarbonate and digestive enzymes The endocrine portion of the pancreas consists of pancreatic islets (islets of Langerhans) There are 2 types of cells in the islets of Langerhans:  alpha cells: secrete glucagon  beta cells: secrete insulin
  44. 44. Dr. Maie Al-Bader - Endocrinology 2013 44
  45. 45. Dr. Maie Al-Bader - Endocrinology 2013 45 Abnormalities – Diabetes Mellitus• DIABETES MELLITUS is characterized by: • Fasting hyperglycemia • Glucose in the urine• Type I diabetes (also known as juvenile-onset diabetes or insulin-dependent diabetes mellitus [IDDM]). It occurs: • in 10% of cases • when there is lack of insulin secretion as a result of destruction of the beta cells• Type II diabetes (also known as maturity-onset diabetes or insulin independent diabetes mellitus [NIDDM]). It occurs: • in 90% of cases of diabetes • patients are usually overweight • there is a larger amount of insulin secretion, however, decreased tissue sensitivity to insulin
  46. 46. Dr. Maie Al-Bader - Endocrinology 2013 46Long Term Complications of Diabetes Mellitus