Chapter 20

1. Chapter 20 The Endocrine System McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

2. Endocrine System Overview • Glands • Pituitary • Thyroid • Parathyroid • Adrenal • Pineal • Thymus • Also areas of the • Pancreas • Gonads • Hypothalamus McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

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4. Endocrine System Organization • Glands – secrete hormones into blood • Hormones – chemical messengers • Receptor organs – react to chemical messages McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

5. Types of Hormones • 2 General Categories • Steroid-derived hormones • Amino acid–synthesized hormones • Amine • Polypeptide McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

6. Hormone–Target Cell Specificity • Hormones alter cellular reactions of specific target cells by • Stimulating DNA to alter rate of protein synthesis • Altering rate of enzyme activity • Altering plasma membrane transport via second messengers • Inducing secretory activity McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

7. Hormone–Receptor Binding • A target cell’s activation is dependent upon • Hormone concentration in blood • Sensitivity of receptor for the hormone • upregulation • downregulation • Number of target cell receptors McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

8. Cyclic AMP: The Intracellular Messenger • Binding of amine-based hormones to receptor sites may activate the enzyme adenylate cyclase. • Adenylate cyclase catalyzes the degradation of ATP to cyclic 3’5’adenosine monophosphate (cyclic AMP). • Cyclic AMP then acts to activate protein kinases that alter cellular activity. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

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10. Effects on Enzymes • Enzyme activity may be altered in one of three ways. • Stimulate enzyme production • Allosteric modulation • Activating inactive forms of the enzyme McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

11. Factors that Determine Hormone Levels • Quantity synthesized • Rate of catabolism of secretion into blood • Quantity of transport proteins present • Changes in plasma volume McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

12. Patterns of Hormone Release • Most respond to peripheral stimuli. • Others have a diurnal variation: cycles may be • Daily • Several weeks McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

13. Resting and Exercise-Induced Endocrine Secretions • Hormones • Immediate response to exercise • Training adaptation McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

14. Anterior Pituitary Hormones • Releasing factor • Proopiomelanocortin (POMC) • Neurotransmitters McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

15. Growth Hormone • GH or somatotropin • Facilitates protein synthesis • Stimulated by exercise • Modulates metabolic mixture • Stimulates fatty acid release • Inhibits cellular glucose uptake McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

16. Insulin-Like Growth Factors • IGFs or somatomedins • Travel in blood to interact with specific receptors • Transport influenced by • Binding proteins in muscle • Nutritional status • Plasma insulin levels McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

17. Thyrotropin • Thyroid-stimulating hormone (TSH) • Regulates hormone secretion by the thyroid • Maintains growth and development of thyroid • Increases thyroid cell metabolism McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

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19. Adrenocorticotropic Hormone • ACTH (corticotropin) • Increases mobilization of fatty acid from adipose tissue • Increases gluconeogenesis • Stimulates protein catabolism • ACTH increases during exercise depending upon intensity and duration. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

20. Prolactin • Prolactin (PRL) initiates and supports milk secretion. • Levels increase at high exercise intensities • May inhibit ovarian function McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

21. Gonadotropic Hormones • Follicle-stimulating hormone (FSH) • Initiates follicle growth in ovaries • Stimulates estrogen secretion • Luteinizing hormone (LH) • Complements FSH action • Stimulates sperm growth and testosterone secretion in testes McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

22. Posterior Pituitary Hormones • ADH or vasopressin • Increases water retention by kidneys • Stimulated by exercise • Helps conserve body fluids • Oxytocin • Important during birthing and nursing McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

23. Thyroid Hormones • T3– triiodothyronine • T4 – thyroxine • Increases metabolism of cell • Help regulate growth and development • Help maintain BP • Exercise increases T4 ~ 35% McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

24. Parathyroid Hormones • Control blood Ca2+ levels • Its release is influenced by blood concentration of Ca2+. • PTH results in • Bone release of Ca2+ • Increased calcium reabsorption by kidneys • Increased calcium absorption by intestinal mucosa • Exercise may increase PTH. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

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26. Adrenal Hormones • Adrenal medulla secretes catecholamines. • Epinephrine • Increases glycogenolysis • Increases lipolysis • Norepinephrine • Increases lipolysis • Relative exercise stimulates release intensity. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

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28. Adrenocortical Hormones • Mineralocorticoids • Glucocorticoids • Gonadocorticoids or androgens McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

29. Mineralocorticoids: Aldosterone • Regulates sodium and K+ in extracellular fluid • Cellular response to aldosterone is slow • > 45 minutes exercise is required to see its effects • Influence is mainly on recovery. • Renin–angiotensin mechanism McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

30. Glucocorticoids • Cortisol is the primary glucocorticoid. • Promotes protein breakdown to amino acids • Blunts the effects of insulin • Increases lipolysis • Increases gluconeogenesis • Net effect = mobilization of fuel McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

31. Gonadocorticoids • Produced in adrenal cortex • Similar actions to sex steroids • Dehydroepiandrosterone exerts effects similar to testosterone. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

32. Gonadal Hormones • Produced in reproductive glands • Testosterone • Estradiol • Progesterone McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

33. Pancreatic Hormones • Insulin • Mediates glucose metabolism • Affects fat synthesis • Facilitates protein synthesis • Stimulates glucose transporters (GLUTs) • Glucagon • Increases blood glucose • Increases glycogenolysis in the liver McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

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35. Metabolic Syndrome X • Insulin resistance • Hyperinsulinemia • Dyslipidemia • Hypertension McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

36. Insulin Actions and Impaired Glucose Homeostasis • Type 1 diabetes • Typically occurs in younger individuals • 5 – 10% of all cases • Exercise has greater metabolic effects. • Type 2 diabetes • Tends to occur after 40 • Often produces reduced exercise tolerance McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

37. Glucagon • Secreted by Islets of Langerhans • Stimulates glycogenolysis • Stimulates gluconeogenesis • Release occurs later in exercise. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

38. Other Glands and Hormones • Liver • Somatomedins • Small intestine • Secretin • Gastrin • Cholecystokinin • Hypothalamus • Somatoliberin McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

39. Anterior Pituitary Hormones • Growth hormone • ACTH • PRL • FSH, LH • Testosterone McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

40. Gender Differences • Women • Exercise may affect FSH and LH levels. • Men • Endurance training affects testosterone and PRL levels. • LH and FSH not affected McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

41. Posterior Pituitary Hormones • ADH • Oxytocin McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

42. Parathyroid Hormone • Enhanced by endurance training McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

43. Adrenal Hormones • Aldosterone • Cortisol • Epinephrine and norepinephrine McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

44. Pancreatic Hormones • Insulin • Glucagon McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

45. Resistance Training and Endocrine Function • Resistance training adaptations affected by • Testosterone • Growth hormone McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

46. Opioid Peptides and Exercise Neuropeptides released by the brain • ß-lipotropin • ß-endorphin • Dynorphin • Activate specific opioid receptor sites • Inhibit anterior pituitary hormones, influencing menstrual cycle • May induce the exercise “high” McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

47. Exercise, Infectious Illness, Cancer, and Immune Response • The influence of exercise on immune function generally follows a J-shaped curve. • Exercise in the optimal range seems to aid immune function. • Overtraining may impair immune function. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

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