1. THYROID PHYSIOLOGY Mohit Chhabra Roll no. 47 Guided by Dr. Mohit Joshi

2. OBJECTIVES Understand relevant microscopic anatomy Grasp basic concepts of: – Iodine metabolism – Thyroid Hormone Synthesis – Regulation of Thyroid hormone – Actions of thyroid hormone

3. MICROSCOPIC ANATOMY OF THYROID Thyroid Follicular Unit C Cells

5. IODINE METABOLISM

6. THYROID HORMONE SYNTHESIS 1.Thyroglobulin is synthesized in RER of Follicular Cells 2.Formation and transport of Tg in exocytotic vesicles into the lumen 3.Iodide transport 4.Iodide oxidation 5.Iodide Storage in lumen 6.Endocytosis by pseudopods & colloid droplet formed 7.Fusion with lysosomes Hydrolysis & Secretion 8.Deiodination THYROID PEROXIDASE

8. THYROID HORMONES Occurs in 2 forms Free form in plasma Bound form – Bound to:  Albumin  TBG  TBPA Fluctuations in binding

9. REGULATION T3 and T4 levels play a pivotal role Negative feedback loop Affect on TSH and TRH Auto regulatory mechanisms

11. MECHANISM OF ACTION Thyroid hormone is LIPOPHILIC Binds to nuclear receptors in the nucleus Appropriate Hormone Response Element comes into action Transcription and Translation occurs with respect to the function of the hormone in that cell

13. ACTIONS OF THYROID HORMONES Calorigenic Growth & Development & Effects on Nervous System Effects on Cardiovascular System Effects on carbohydrate metabolism Effects on cholesterol metabolism Effect on Catecholamines

14. SOURCES  Google Image Search  Bailey & Love’s Short Textbook of Surgery  Sabiston’s Textbook of Surgery 18 th edition  Ganong’s Review of Physiology