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Hormonal Regulation of Growth, Development, and Metabolism

Hormonal Regulation of Growth, Development, and Metabolism. Chapter 9.2 McGraw-Hill Ryerson Biology 12 (2011). METABOLISM. Thyroid Gland is located in front of the trachea. It produces hormones: Thyroxine (T4) ‏ Triiodothyronine (T3) ‏ T4 and T3 regulate body metabolism and

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Hormonal Regulation of Growth, Development, and Metabolism

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  1. Hormonal Regulation of Growth, Development, and Metabolism Chapter 9.2 McGraw-Hill Ryerson Biology 12 (2011)

  2. METABOLISM • Thyroid Gland is located in front of the trachea. • It produces hormones: • Thyroxine (T4)‏ • Triiodothyronine (T3)‏ • T4 and T3 regulate • body metabolism and • growth and differentiation of tissues

  3. T4 and T3 • Tyrosine based hormones, dependent on iodine for production. • Lipophilic, travel through blood bound to a protein, thyroxine binding globulin (TBG) and cross the cell membrane easily to interact with nuclear receptors, thyroid hormone receptor. • T4 has a longer half-life than T3 and outnumbers T3 by 20:1 in the bloodstream, but T3 is 4 times as potent (more active). • Circulating T4 is converted to T3 by the removal of iodine. T4 is considered a precursor to T3.

  4. Effects of T4 and T3 • T4 and T3 help our body oxidize sugars and nutrients (proteins, fats) at a faster rate. • All the energy of glucose is transferred to heat and ATP, (no storing of glucose) and ATP is consumed during activity, therefore there is no weight gain. • Also increase cardiac output, heart rate, breathing rate, and production of RNA polymerases (so increased protein synthesis – as well as metabolism)

  5. REGULATION of METABOLISM Metabolic rate decreases Hypothalamus TRH Pituitary TSH Thyroid Thyroxine Increase metabolism inhibits

  6. REGULATION of METABOLISM • Metabolic rate decreases • hypothalamus sends thyroid releasing hormone (TRH) to the anterior pituitary • Anterior pituitary releases thyroid stimulating hormone (TSH) • TSH acts on thyroid to stimulate release of thyroxine. • thyroxine raises metabolism by increasing sugar usage by body tissues • thyroxine levels feedback on hypothalamus and pituitary to inhibit further release of TRH /TSH

  7. Thryoid Disorders • Hypothyroidism: low thyroid secretions • glucose is not oxidized as quickly, and excess glucose is converted to glycogen and stored. • once glycogen stores are filled, excess sugar is stored as fat. http://www.holisticprimarycare.net/topics/topics-h-n/healthy-aging/94-the-clinical-picture-of-hypothyroidism

  8. Thyroid Disorders: Goiter Goiter • Lack of iodine for producing T4 and T3 • TSH produced continuously in effort to increase levels of T4 and T3 • NO Feedback because functional T4 and T3 not formed • Overstimulated thyroid enlarges Metabolic rate decreases Hypothalamus TRH Pituitary TSH Thyroid

  9. Other Hormones of the Thyroid Gland • Thyroid Gland also produces calcitonin • Decrease calcium in blood by absorption from blood to bones http://ncwcbio101.wordpress.com/

  10. Parathyroid Glands (on the thyroid) produce Parathyroid hormone (PTH): • increase Calcium in blood by calcium release from bones, and reabsorption at kidneys, intestines) • Also increases production of active Vitamin D • Normal blood levels of calcium are important for proper functioning of (for ex.) the nervous system and blood clotting.

  11. Other Metabolic Hormones • In addition to TSH, the Pituitary Gland also produces Growth hormone (somatotropin) • Increase Protein synthesis, Breakdown of fats • Abnomal levels lead to: dwarfism, gigantism, acromegaly

  12. Homework • Pg 403 #4, 6, 8, 10, 11

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