1 / 22

THYROID PHYSIOLOGY

THYROID PHYSIOLOGY. Jack L. Leonard, Ph.D. office: S4-100L2B phone: X66687 email: jack.leonard@umassmed.edu http://users.umassmed.edu/jack.leonard. THE THYROID GLAND. www.univ-st-etienne.fr/lbti/Mednucl/AtlasEnd/thyroide/. THYROID GLAND HISTOLOGY.

Download Presentation

THYROID PHYSIOLOGY

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. THYROID PHYSIOLOGY Jack L. Leonard, Ph.D. office: S4-100L2B phone: X66687 email: jack.leonard@umassmed.edu http://users.umassmed.edu/jack.leonard

  2. THE THYROID GLAND www.univ-st-etienne.fr/lbti/Mednucl/AtlasEnd/thyroide/

  3. THYROID GLAND HISTOLOGY http://arbl.cvmbs.colostate.edu/hbooks/pathphys/endocrine/thyroid/anatomy.html

  4. THYROID FOLLICULAR CELL MORPHOLOGY

  5. OH OH I I I I I O O NH2 NH2 I I OH OH O O 3,5,3’-Triiodothyronine (T3) THYROID HORMONES Thyroxine (T4)

  6. FEEDBACK REGULATION THE HYPOTHALAMIC-PITUITARY-THYROID AXIS • Hormones derived from the pituitary that regulate the synthesis and/or secretion of other hormones are known astrophic hormones. • Key players for the thyroid include: TRH - Thyrophin Releasing Hormone TSH - Thyroid Stimulating Hormone T4/T3 - Thyroid hormones

  7. PITUITARY-THYROID AXIS – – + HM Goodman, BASIC MEDICAL ENDOCRINOLOGY 3rd Ed.

  8. PITUITARY-THYROTROPE CELL HM Goodman, BASIC MEDICAL ENDOCRINOLOGY 3rd Ed.

  9. TSH REGULATION OF THYROID FUNCTION • TSH binds to specific cell surface receptors that stimulate adenylate cyclase to produce cAMP. • TSH increases metabolic activity that is required to synthesize Thyroglobulin (Tg) and generate peroxide. • TSH stimulates both I- uptake and iodination of tyrosine resides on Tg.

  10. ClO4-, SCN- organification NaI symporter (NIS) Propylthiouracil (PTU) blocks iodination of thyroglobulin Thyroid peroxidase (TPO) ION TRANSPORT BY THE THYROID FOLLICULAR CELL BLOOD I- COLLOID I-

  11. Iodination of Tyr residues of Tg TSH TSH receptor TPO THYROGLOBULIN SYNTHESIS IN THE THYROID FOLLICULAR CELL COLLOID

  12. T4 T3 DIT MIT I- TSH TSH receptor THYROID HORMONE SECRETION BY THE THYROID FOLLICULAR CELL COLLOID

  13. THYROID HORMONES IN THE BLOOD • Approximately 99.98% of T4 is bound to 3 serum proteins: Thyroid binding globulin (TBG) ~75%; Thyroid binding prealbumin (TBPA or transthyretin) 15-20%; albumin ~5-10% • Only ~0.02% of the total T4 in blood is unbound or free. • Only ~0.4% of total T3 in blood is free.

  14. NH2 NH2 I OH I OH OH “Step up” “Step down” I O O O I T4 I I OH I R OH I R I O O I T3 rT3 I OH I R O 3,3’-T2 R = THYROID HORMONE METABOLISM

  15. THYROID HORMONE DEIODINASES • Three deiodinases (D1, D2 & D3) catalyze the generation and/disposal of bioactive thyroid hormone. • D1 & D2 “bioactivate” thyroid hormone by removing a single “outer-ring” iodine atom. • D3 “inactivates” thyroid hormone by removing a single “inner-ring”iodine atom. • All family members contain the novel amino acid selenocysteine (SeC) in their catalytic center.

  16. extracellular domain A B E intracellular domain COOH D C NH2 EXISTS AS A DIMER BASIC ORGANIZATION OF THE SELENODEIODINASES

  17. BASICS OF THYROID HORMONE ACTION IN THE CELL

  18. STEROID/THYROID HORMONE FAMILY OF NUCLEAR RECEPTORS

  19. SPECIFIC ACTIONS OF THYROID HORMONE: METABOLIC • Regulates of Basal Metabolic Rate (BMR). • Increases oxygen consumption in most target tissues. • Permissive actions: THincreases sensitivity of target tissues to catecholamines, thereby elevating lipolysis, glycogenolysis, and gluconeogenesis.

  20. SPECIFIC ACTIONS OF THYROID HORMONE: DEVELOPMENT • TH is critical for normal development of the skeletal system and musculature. • TH is also essential for normal brain development and regulates synaptogenesis, neuronal integration, myelination and cell migration. • Cretinism is the term for the constellation of defects resulting from untreated neonatal hypothyroidism.

  21. EXAMPLES OF THYROID DISEASES Hyperthyroidism 1° Hypothyroidism www.hsc.missouri.edu/~daveg/thyroid/thy_dis.html

  22. EXAMPLES OF THYROID DISEASES Juvenile Hypothyroidism Congenital Hypothyroidism www.hsc.missouri.edu/~daveg/thyroid/thy_dis.html

More Related