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Introduction to Endocrine

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  • 1. Introduction to Endocrinology Endocrine (Gk- I separate within) DR. LAXMIKANTA SAY
  • 2. CHEMICAL MESSANGER SYSTEM Neurotransmitter Endocrine hormone Neuroendocrine hormone Paracrine hormone Autocrine hormone Cytokines
  • 3. LOCATION OF ENDOCRINE GLANDS ORGAN HORMONES HEART ANP GIT CCK-PZ, SECRETIN, VIP KIDNEY ERYTHROPOIETIN , 1,25-DHCC PINEAL GLAND MELATONIN SKIN CALCIFEROL(VitD3) LIVER IGF-I, II PLATELET PDGF LYMPHOCYTES IL
  • 4. HORMONES Gk :Horman = “to set in motion” = “to execute” or “to arouse” DEFINITION Secretory products of the ductless glands, which are released in catalytic amounts into blood stream and transported to specific target cells or organs, where they elicit physiologic, morphologic and biochemical responses.
  • 5. CHARECTERESTICS i. Distant target cell ii. Receptor iii. Regulates existing fundamental bodily process but do not initiate cellular reaction. iv. Secreted in extremely low concentration v. Long latent period than neurons. vi. Metabolized rapidly in kidney and liver
  • 6. Functions of Hormones 1. Help regulate:  Chemical composition & volume of     internal environment. Metabolism & Energy balance. Contraction of smooth muscle & cardiac muscle fiber. Glandular secretion. Immune system activities.
  • 7. 2. Control Growth & Development 3. Regulate operation of reproductive system. 4. Help establish circadian rhythms.
  • 8. NEUROENDOCRINE AXIS
  • 9. CLASSIFICATION OF HORMONE HORMONE PROTEIN & PEPTIDE STEROID AMINOACID DERIVATIVE
  • 10. PROTEIN & PEPTIDES  Proteins - more than 200 amino acids  Polypeptide - 100 or more amino acids  Peptide - fewer than 100 amino acids.  Water soluble,  Unbound in plasma,  Synthesized on ribosomes at ER,  Strored as zymogen granules in golgi apparatus  Half life : 6 – 60 minutes.
  • 11. E.g., - Hypothalamus - Anterior & Posterior Pituitary - Pancreas (insulin & glucagon) - Parathyroid - Placenta (HCG & HSM) - Heart (ANP), Stomach (gastrin) - Small Intestine (Secretin & CCK) - Adipocytes (Leptins)
  • 12. CHEMISTRY Peptide Hormone 1 Messenger RNA on the ribosome binds amino acids into a peptide chain called a preprohormone. The chain is directed into the ER lumen by a signal sequence of amino acids. 2 Enzymes in the ER chop off the signal sequence, creating an inactive prohormone. 3 The prohormone passes from the ER through the Golgi complex. 4 Secretory vesicles containing enzymes and prohormone bud off the Golgi. The enzymes chop the prohormone into one or more active peptides plus additional peptide fragments. 5 The secretory vesicle releases its contents by exocytosis into the extracellular space. 6 The hormone moves into the circulation for transport to its target. Golgi complex Endoplasmic reticulum (ER) To target Ribosome Active hormone Transport vesicle Peptide fragment 3 4 6 Secretory vesicle Prohormone Release signal 5 Capillary endothelium 2 1 mRNA Signal sequence Cytoplasm ECF Plasma Preprohormone Figure 7-3
  • 13. STEROIDS  Chemically similar & synthesized from Acetate or Cholesterol. Highly lipid soluble , hydrophobic, Not stored. Consists of 3 Cyclohexyl ring & 1 cyclopentany ring Simple diffusion occurs across cell membrane & interstitial fluid Half life : 60-100 minutes.  E.g., - Adrenal cortex (cortisol & aldosterone) - Ovaries (estrogen & progestrone) - Testes (testosterone) - Placenta (estrogen & progesterone)
  • 14. Steroid Hormones Steroid hormones are derived from cholesterol
  • 15. Derivatives of Amino Acids  Tyrosine Bound to transport proteins Half life : Thyroid hormone – 7-9 min. Epinephrine / Nor-epi : 1- min. E.g., - Thyroid (thyroxine triiodo thyronine) - Adrenal Medulla (epinephrine & norepi)
  • 16. Amine Hormones: Structure Tyrosine-derived amine hormones Figure 7-8
  • 17. Hormone Transport Unbound to plasma protein - Water soluble hormones - Catecholamines, peptides & protein hormones. Bound to plasma protein  Lipid soluble hormones  Steroid –SBP  Testosterone and estrogen- SHBG  Progesterone, cortisol and other corticosteroid Free hormone is the active hormone.
  • 18. Plasma Concentration Hormones are secreted in very low concentration in pulsatile manner. RYTHMS:1. CIRCADIAN (Diurnal) 2. ULTRADIAN
  • 19. Half- Life of some Hormones Class of Hormone Hormone Protein & Peptide Hormones •ADH •Oxytocin •Insulin •Prolactin •Growth Hormone <1 min <1 Min 5 min 12 sec <30 min Amines •Epinephrine •Thyroxin 10 sec 5-7 days Steroid Hormones •Aldosterone •Cortisol Half- Life 30 Min 90-100 Min
  • 20. Hormone Disposal 1. 2. 3. - Target cell uptake & Intracellular degradation. - Metabolic degradation by Liver & Kidney - Urinary & Biliary Disposal Metabolic clearance rate (MCR)  Defines the quantitative removal of hormone from plasma  The bulk of hormone is cleared by liver and kidneys  Only a small fraction is removed by target tissue  protein and amine hormones bind to receptors and are internalized and degraded  Steroid and thyroid hormones are degraded after hormonereceptor complex binds to nuclear chromatin MCR = Rate of disappearance of hormone from plasma / ( ml cleared/ minute ) Concentration of hormone
  • 21. THANK YOU