1 / 15

Growth Hormone

Growth Hormone. Victoria Brown. Structure of hormone. 191 amino acids long Protein structure 4 helices that help it bind its receptor 2 strong sulfide bonds hold the structure together. Structure of receptor. Single-chain glycoprotein receptor

hoai
Télécharger la présentation

Growth Hormone

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. Growth Hormone Victoria Brown

  2. Structure of hormone • 191 amino acids long • Protein structure • 4 helices that help it bind its receptor • 2 strong sulfide bonds hold the structure together

  3. Structure of receptor • Single-chain glycoprotein receptor • 2 binding receptors for each molecule of growth hormone: • GHRI • GHRII • The 2 receptor molecules bind to two structurally distinct sites on opposite sides of a single growth hormone molecule • Binding of the two receptors is sequential, not simultaneous

  4. Where does it come from? • Synthesized and secreted by somatotroph cells (anterior pituitary) in response to growth-hormone releasing hormone (GHRH) from the hypothalamus • Activates gene transcription by cyclic adenosine monophosphate (cAMP) mechanisms

  5. What happens in the cell? • The hormone binds on the outside of the cell, bringing two receptors together • The interaction of growth hormone with its receptor leads to activation of cytoplasmic tyrosine kinases, triggering several enzymatic reactions and signaling processes that stimulate growth

  6. Role in growth • Growth hormone travels through the blood and stimulates the liver to produce a protein called insulin-like growth factor (IGF-1) • In children, IGF-1 stimulates chondrocytes to multiply in the cartilage at the ends of long bones (epiphyseal plate) • This leads to growth in the length of the bones and increases the child's height • In adults, growth hormone plays an important role inrepair and maintenance of the body’s tissues • IGF-1 also acts on immature muscle cells to increase muscle mass

  7. Role in metabolism • Protein metabolism: • Increased amino acid uptake • Increased protein synthesis • Fat metabolism: • Triglyceride breakdown in adipocytes (lipolysis) • Carbohydrate metabolism: • Helps maintain blood glucose levels • Suppresses insulin to prevent uptake of glucose in peripheral tissues • Glucose synthesis in the liver (gluconeogenesis)

  8. Primary Target tissues • Bone • Muscle • Fat

  9. Regulation • 2 hormones from the hypothalamus: • Growth hormone-releasing hormone (GHRH) • Stimulates both the synthesis and secretion of growth hormone • Somatostatin (SS) • Inhibits growth hormone release from somatotroph cells • 1 hormone from the stomach: • Ghrelin • Binds to receptors on somatotroph cells and potently stimulates secretion of growth hormone

  10. Negative Feedback • IGF-I • Directly suppresses the somatotroph cells • Stimulates the release of somatostatin from the hypothalamus • Growth hormone • Directly suppresses the somatotroph cells • Inhibits GHRH secretion

  11. Feedback

  12. Normal blood values • 1 - 9 ng/mL (male) • 1 - 16 ng/mL (female) • Natural levels of growth hormone fluctuate during the day, depending on: • Stress • Exercise • Nutrition • Sleep

  13. Too much growth hormone? • Usually from a tumor on the pituitary • Begins before puberty • Gigantism • Robert Wadlow • At birth: 8.5 lbs • 5 years old: 5’ 4” and 105 lbs • Adult: 8’ 11” and 490 lbs • Begins after puberty • Acromegaly • Enlarged face, hands, and feet • High blood pressure and heart disease • A number of metabolic derangements, including hyperglycemia

  14. Too little growth hormone? • Begins before puberty: • Dwarfism • Begins after puberty: • Reduction of muscle/bone strength and mass among other debilitating factors

  15. “There are no great limits to growth because there are no limits of human intelligence, imagination, and wonder.” —Ronald Reagan

More Related