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Fig 7-2

__________________: the study of hormones, their receptors, the intracellular signaling pathways they invoke, and the diseases and conditions associated with them. What are hormones? Major endocrine glands? Physiological processes controlled by hormones?. Fig 7-2. Hormones.

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Fig 7-2

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  1. __________________: the study of hormones, their receptors, the intracellular signaling pathways they invoke, and the diseases and conditions associated with them. • What are hormones? • Major endocrine glands? • Physiological processes controlled by hormones? Fig 7-2

  2. Hormones • Known since ancient times • Secreted by cells into the blood • Transported to distant targets • Effective at very low concentration • Bind to receptors • Hormone action must be of limited duration

  3. Classification of Hormones • 3 main types: • Peptides and proteins • Steroids • Amines Differ on basis of synthesis, storage, release, transport and cellular mechanism of action (review Table 7-1)

  4. Peptide (Protein) Hormones • Synthesis as preprohormone post-translational modification to prohormone then hormone • Storage – release? • Short half-life (mins.) • Most common type Fig 7-4 Fig 7-3

  5. Cellular Mechanism of Action for Peptide Hormones • Lipophobic  how does message get into cell? • Usually rapid cellular response because existing proteins are modified • cAMP 2nd messenger system most common

  6. Steroid Hormones • All derived from cholesterol • Where synthesized? • Storage – release? • Transport in blood? • Longer half-life • Mechanism of action Fig 7-6 Fig 7-7

  7. Amine Hormones • Derived from one or two amino acids • 3 groups • Tryptophan  Melatonin • Tyrosine  Catecholaminesbehave like peptide hormones • Tyrosine  Thyroid hormonesbehave like steroid hormones Fig 7-8

  8. Control of Hormone Release All endocrine reflex pathways have similar components • Stimulus / input signal • Integration (where?) • Output signal (hormone / neurohormone) • Physiological action • Negative feedback – turns off reflex One Hormone may follow > 1 reflex pathway pattern Fig 7-9

  9. Simple Endocrine Reflex Endocrine cell acts as sensor AND integrating center  no afferent pathway  responds by secreting hormone Example: PTH  increases [Ca2+] in plasma Fig 7-10 Fig 6-31/➅

  10. NeurohormoneReflex NH release by modified neurons upon NS signal • 3 major groups of Neurohormones: • Catecholamines from adrenal medulla • Hypothalamic neurohormones from posterior pituitary • Hypothalamic neurohormones acting on anterior pituitary Fig 6-31/②

  11. Neurohormones of Posterior Pituitary • Other name of gland? • 2 neurohormones • Both are peptides (9 aa) transported in secretory vesicles via axonal transport Fig 7-12

  12. Anterior Pituitary • Secretes 6 Hormones (names?) • A Trophic (tropic) hormone controls the secretion of another hormone • Hypothalamic trophic hormones and the hypothalamic-hypophyseal portal system Fig 7-13

  13. Hypothalamus IC1 Ant. pituitary IC2 Endocrine gland IC3 Target tissue Negative Feedback Loops in the Hypothalamic-anterior pituitary axis Hormones serve as negative feedback signals: Short-loop vs. long-loop negative feedback. Feedback patterns important in diagnosis of ES pathologies

  14. Hormone Interactions Multiple hormones can affect a single target simultaneously Three types of hormone interactions: • Synergism • Permissiveness • Antagonism

  15. Synergism • Combined action of hormones is more than just additive! • Example: Blood glucose levels & synergistic effects of glucagon, cortisol and epinephrine Fig 7-18

  16. Permissiveness Hormone A will not exert full effect without presence of hormone B. Example: Thyroid hormone & growth hormone Antagonism Antagonistic hormones have opposing physiological actions – Hormone B diminishes the effect of hormone A (mechanisms?) Hormone Antagonists and Cancer: Tamoxifen

  17. Endocrine Pathologies “Unbalance leads to disease” Due to: • Hypersecretion (excess) • Hyposecretion (deficiency) • Abnormal target tissue response

  18. Hypersecretion: • Due to ? • Iatrogenic (could lead to gland atrophy) • ________ • Symptoms: Exaggerated Effects Examples: • Cushing’s Syndrome • Gigantism • Graves disease

  19. Example:Hyperthyroidism(Review pp. 756 – 761) Most common cause: Graves' disease Autoantibodies (TSI) bind to TSH receptor and stimulate thyroid hormone production This activation by TSI is not subject to the normal negative feedback loop. Left exophthalmus in Graves disease

  20. Hyposecretion: • Due to ? • Symptoms: Normal effects of hormone diminished or absent Examples: • Addison’s disease • Dwarfism • Hypothyroidism

  21. Example:Hypothyroidism Most common cause in US:chronic autoimmune thyroiditis (Hashimoto's thyroiditis = Chronic thyroiditis) Other causes • surgical removal of the thyroid gland • radioactive iodine treatment • external radiation • a deficiency in dietary iodide consumption (=endemic or primary goiter)

  22. Hypothyroidism cont. Symptoms: During childhood: stunted growth retardation lethargy low body temp. In adulthood: Bradycardia weight gain lethargy low body temp.

  23. Abnormal Tissue Responsiveness Hormone levels normal, target unresponsive Due to: • Abnormal hormone / receptor interaction • Abnormal signal transduction

  24. Diagnosis of Endocrine Pathologies • Primary Pathology • Defect arises in last integration center in the reflex • Examples? • Secondary Pathology • Defect arises in one of the trophic integration centers • Examples?

  25. Which of the sets of lab values below would indicate Grave’s disease? Explain.

  26. The End Graves’ disease

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