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Hormones affecting metabolism


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Hormones affecting metabolism

  1. 1. Part 3: Metabolism RegulationEndocrine System
  2. 2. Thyroid GlandLocation:base of neckventral surface of tracheaBelow & anterior to larynxOne of the largest endocrineglands in the bodyFunctional Unit: Follicle
  3. 3. Thyroid GlandStructure:Two lobes4 cm long, 1-2 cm wideconnected by a narrowneck (isthmus)Color: Red / BrownProduces thyroidhormones
  4. 4. Thyroid Hormones: T3 and T4T4: Thyroxine / TetraiodothyronineT3: TriiodothyronineRequires iodination
  5. 5. Comparing T3 and T4T3 (Triiodothyronine) T4 (Thyroxine)# of Iodine atoms 3 4% in blood 0.3% 0.03%% produced bythyroid glands~ 20% ~ 80%Potency 4X more than T4 Not veryHalf Life Span Shorter (1-2.5 d) Longer (5-7 d)Main PurposeRegulate basalmetabolic processesConversion to T3
  6. 6. QuestionsWhy is more T4 made than T3?Why have T4 at all when T3 is so much moreeffective?
  7. 7. Thyroid Hormones PropertiesPeptide hormoneDerived from the amino acid tyrosineNot very soluble in bloodHydrophobic and will diffuse into cellsThyroid hormone receptorIntracellular, in nucleusHas greater affinity for T3 than T4
  8. 8. Thyroid Hormones FunctionAct on nearly every cell in the bodyRegulates metabolismIncrease glucose metabolismIncrease protein synthesisIncrease oxygen consumption (blood pressure, heart rate)Regulates growth and tissue differentiationDigestionReproductionBone growthMuscle toneDevelopment of nerve cells
  9. 9. Thyroid RegulationStimulus: change in metabolicrate (decreased metabolism)Detected by hypothalamus
  10. 10. Thyroid Regulation:Neuroendocrine pathwayLocation HormoneHypothalamus TSH Releasing Hormone /Thyrotropin releasing hormone(TRH)Anterior Pituitary Thyroid Stimulating Hormone(TSH)Thyroid gland Thyroid hormones T3 & T4
  11. 11. Thyroid Regulation: FeedbackHigh levels of T3/T4in blood turn offproduction of TRHand TSH
  12. 12. decreased metabolismIncreased blood sugarAnterior pituitaryrelease TSHHypothalamusrelease TRHincrease sugarmetabolismThyroid RegulationThyroid glandreleased T3/T4
  13. 13. Thyroid Regulation: FeedbackStimulus Low T3/T4 High T3/T4Effect on TRH Stimulated InhibitedEffect on TSH Increase InhibitedEffect on T3/T4 Increase Decrease
  14. 14. Thyroid DisordersHyperthyroidismPlummer’s diseaseGrave’s diseaseHypothyroidismHashimoto’s thyroiditis
  15. 15. Hyperthyroidism: Goiterenlarged thyroid glanddue to overactivity
  16. 16. Cause: Iodine deficiencyLow iodine levels meanslow levels of T3/T4Body tries tocompensate by workingthe thyroid gland moreto make more T3/T4
  17. 17. Hyperthyroidism Symptomshigh T4 (thyroxine) releasehigh glucose metabolism:weight loss with increased appetiteanxietyincreased heat release
  18. 18. Cause: Nodules(Plummer’s Disease)Nodule: small lumpstoxic multinodular goiter (many nodules)
  19. 19. Cause: Autoimmunity(Grave’s Disease)Thyroid stimulating immunoglobulin (TSI)An antibody that targets TSH receptors tostimulate TSH secretion (from anterior pituitary)TSI not subject to negative feedback8x more common in womenbetween ages 20 – 40
  20. 20. Grave’s Disease Symptomsprotruding eyeseye irritation and double vision
  21. 21. Hyperthyroidism: Other CausesOveractive thyroid gland that produces toomany thyroid hormones without requiringstimulation by TSHInflammation of the thyroid (thyroiditis)Pituitary tumorsToo much thyroid hormone medicationExcessive intake of iodine
  22. 22. Hyperthyroidism Treatment:Drug TherapyAnti-thyroid drugs (suppressive medication)Block amount of thyroid hormone in theblood streamPrevent iodine from entering thyroid gland
  23. 23. Hyperthyroidism Treatment:Radioactive Iodine TherapyGiven when drug therapy failsRadioactive iodine-131Damages thyroid cells over timeThyroid gland shrinks returning thyroidhormone to normal level.
  24. 24. Hyperthyroidism Treatment:SurgeryThyroidectomy: removal of all or some partsof the thyroid glandPost-surgery, thyroid replacement drugsmay be necessary, depending on how muchof the thyroid gland is left.
  25. 25. Hypothyroidism Symptomslow thyroxine releaselow glucose metabolismweight gainfatiguedecreased heart release4x more common in women than menusually between ages 35 – 60
  26. 26. Hypothyroidism
  27. 27. Cause: Autoimmunity(Hashimoto’s Thyroiditis)Immune system attacks thyroid glandInflammation of the thyroid gland20x more common in womenbetween the ages 30 – 50Treatment: thyroid hormone supplements
  28. 28. Hypothyroidism: Other CausesIodine deficiencyThyroid gland dysfunction: producing toolittle thyroid hormonesAfter radiation therapy with radioactiveiodineAfter a thyroidectomy
  29. 29. Comparing SymptomsHyperthyroidism HypothyroidismWeight Loss but good appetite GainBodyFunctionIncreased bowel movementLight/absent menstrualperiodsConstipationHeavy menstrualperiodsTemperature Warm/moist skin, Feel hot Feel coldNeurological Fatigue, InsomniaIrritability, NervousnessFatigueSlowed thinkingOthers Bulging eyes, goiter Dry skin
  30. 30. Calcium RegulationAntagonistic hormones:PTHcalcitonin
  31. 31. Calcium Storage99% stored in bonesIn cells: mitochondria and ERIn skeletal muscles:sarcoplasmic reticulum (SR)
  32. 32. Calcium FunctionMusclesCa levels inside muscle cells change when musclescontractNervesCa stimulate release of neurotransmitters
  33. 33. Bone CellsOsteoblast: bone-forming cells, take Cafrom blood to build into bonesOsteoclast: break down Ca in bones andrelease into blood
  34. 34. Parathyroid Gland4 small oval shaped glandsLocated behind the thyroidglandsEach lobe of thyroid gland isadjacent to 2 parathyroid glandSecretes parathyroid hormone(PTH)
  35. 35. Parathyroid Hormone (PTH)Peptide hormoneContinuously produced (tonic secretion)Stimulated by a decrease in blood calcium(hypocalcemia)
  36. 36. PTH TargetsBoneInduces osetoclastDecompose bone to release stored Ca into bloodKidneyStimulates reabsorption of calciumConverts vitamin D precursor to active vitamin D
  37. 37. Vitamin DSteroid hormoneCan be ingested in food or formed in skinwhen exposed to sunlightActivated form of vitamin D reinforces theeffect of PTHIncrease calcium in blood
  38. 38. Vitamin D TargetsBone: release CaIntestine: Stimulates absorption of calcium
  39. 39. Calcium RegulationLow blood Ca(hypocalcemia)PTH releasedBy parathyroid glandsActivation ofVitamin DBoneKidney IntestineIncreasereabsorptionStimulateosteoclastDecomposeboneIncreaseabsorption
  40. 40. CalcitoninPeptide hormoneSecreted by thyroid glandStimulated by increase of blood calcium(hypercalcemia)Antagonist of PTH: decreases blood calcium
  41. 41. Calcitonin TargetsBoneStimulates Ca uptake into bonesInhibits osteoclastsLess bone tissue removalKidneyInhibits Ca reabsorptionIncreases rates of Ca loss by urinatinghigher concentration of Ca in urineIntestineinhibits Ca absorption
  42. 42.
  43. 43. HypoparathyroidismCauses:absent parathyroid from birthaccidental removal upon thyroid removalSymptoms:decreased Ca levels in blood (hypocalcemia)sensitive nervesuncontrollable spasms of the limbsTreatmentdaily calcium and vitamin D supplements
  44. 44. Hypocalcemia SymptomsTetanyan increased excitability of the nerves (nerves aremore likely to respond to less intense stimuli)results in uncontrollable, painful spasms of theface, hands, arms, and feetSeizures
  45. 45. hypocalcemiaparathyroid gland release PTHincreased Ca2+levelsincreased Ca2+uptakein intestines (diet) &kidneys (reabsorption)increases osteoclastactivityactivation of vitamin D;required for Ca2+absorptionHypocalcemia
  46. 46. HyperparathyroidismCauses:tumors on the parathyroid glandSymptoms:kidney stonesaches & painsosteoporosisdepression & fatigueTreatment:removal of parathyroid tissue
  47. 47. Hypercalcemia SymptomsStones (Kidney Stones)Bones (Bone Pain)Groans (Constipation)Moans (peptic ulcer, pancreatitis)Overtones (Depression/ Confusion)
  48. 48. hypercalcemiathyroid gland release calcitonindecreased Ca2+levelsinhibits Ca2+absorptionby intestinesdecreases osteoclastactivityHypercalcemia
  49. 49. OsteoporosisLoss of density in bones, leading to fragilebonesCausesHyperparathyroidism Hyperactive Parathyroid (high levels of PTH)Hypovitaminosis D Lack of Vitamin D in diet Decrease in enzyme catalyzing Vitamin DOver activity of osteoclasts
  50. 50. Osteoporosis Symptomsincrease risk of bone fracturesJoint painkyphosis (hunchback)