1. Illinois State University ä Hormonal Influences on Human Body Composition

2. Illinois State University Hormones ä Hormones exert major, determining effects on body composition.

3. Illinois State University The Endocrine System ä Gland ä Hormone ä Target organ or tissue.

4. Illinois State University Hormones ä Hormones can be classified as either steroidal or nonsteroidal. ä Steroid hormones are lipid soluble, and most are formed from cholesterol. ä Nonsteroid hormones are proteins, peptides, or amino acids.

5. Illinois State University Hormones ä Hormones are generally secreted into the blood and then circulate through the body to exert an effect only on their target cells.

6. Illinois State University Hormones ä Steroid hormones pass through cell membranes and bind to receptors inside the cell. ä They use a mechanism called direct gene activation to cause protein synthesis.

7. Illinois State University Hormones ä Non-steroidal hormones cannot enter cells easily, so they bind to receptors on the cell membrane. ä This activates a second messenger within the cell which in turn can trigger numerous cellular processes.

8. Illinois State University Hormones ä Secretion of most hormones is regulated by a negative feedback system.

9. Illinois State University Hormones ä The number of receptors for a specific hormone can be altered to meet the body’s demands.

10. Illinois State University Hormones ä Key point - the pituitary gland was once thought to be the master endocrine gland solely in control of many other glands and organs.

11. Illinois State University Control ä It is now recognized that the pituitary gland is largely controlled by the hypothalamus.

12. Illinois State University Hormones ä Both peptide and steroid hormones, alone or in combination, exert profound changes on both the lean and fat compartments of body composition.

13. Illinois State University Hormones ä The main physiological steroid hormones affecting body composition include: cortisol, testosterone, and 17-beta-estradiol.

14. Illinois State University Hormones ä The effects of these steroid hormones are dependent on the interactions of GH and insulin.

15. Illinois State University Pituitary Hormones Anterior Lobe ä Somatotropin (hgH) - Impacts all cells of the body. ä Major role in maturation, protein synthesis, use of fat, and CHO sparing.

16. Illinois State University Thyroid Hormone ä Thyroxine and triiodothyronine - Impact all cells in the body. ä Increases rate of cellular metabolism, increases heart rate and force of contraction.

17. Illinois State University Adrenal Hormones Medulla ä Epinephrine - Impacts most cells of the body. ä Mobilizes glycogen, increases skeletal muscle blood flow, increases heart rate and contractility, increases oxygen consumption.

18. Illinois State University Adrenal Hormones Medulla ä Norepinephrine - impacts most cells of the body through vasoconstriction which increases blood flow, increases heart rate and contractility, increases VO 2.

19. Illinois State University Adrenal Hormones Cortex ä Glucocorticoids (cortisol) - impacts most cells of the body. ä Controls metabolism of all fuels and has an anti-inflammatory action.

20. Illinois State University Adrenal Hormones Cortex ä Androgens and estrogens - impacts sex organs. ä Responsible for development of secondary sexual characteristics.

21. Illinois State University Pancreatic Hormones ä Insulin - impacts all cells of the body. ä Regulates blood glucose levels. ä Increases the utilization of glucose and the synthesis of fat.

22. Illinois State University Pancreatic Hormones ä Glucagon - impacts all cells of the body. ä Increases blood glucose levels and stimulates the breakdown of protein and fat.

23. Illinois State University Gonadal Hormones Testes ä Testosterone - affects sex organs and muscles. ä Responsible for the development of male secondary sexual characteristics.

24. Illinois State University Gonadal Hormones Ovaries ä Estrogen - affects sex organs and adipose tissue. ä Responsible for the development of female secondary sexual characteristics.

25. Illinois State University Cortisol ä Excess cortisol secretion causes wasting of lean body mass, particularly muscle.

26. Illinois State University Cortisol ä The interactions of insulin become important for the net effect of glucocorticoids on muscle mass as well as on adipose tissue mass and distribution.

27. Illinois State University Cortisol ä In human adipose tissue, the acute short- term effects of cortisol seem to be essentially absent.

28. Illinois State University Cortisol ä In long-term (days) experiments under fully controlled conditions, the effects are easier to detect.

29. Illinois State University Cortisol ä In the presence of insulin, cortisol by itself has a rather weak inhibitory effect on cathecholamine-induced lipolysis, but cortisol induces a marked “permissive” effect by GH on lipolysis. ä Result – decreased fat mass and muscle mass

30. Illinois State University Cortisol ä The integrated effect of cortisol on lipolysis would not be expected to increase lipolysis because, with cortisol excess, GH secretion is blunted.

31. Illinois State University Cortisol ä Furthermore, insulin secretion is elevated, with its consequences for lipid mobilization.

32. Illinois State University Cortisol ä The effects of glucocorticoids on adipose tissue are regionally specific.

33. Illinois State University Testosterone ä The effects of testosterone on lean body mass are well established, e.g., the elevation of muscle mass and reduction of adipose tissue stores.

34. Illinois State University Testosterone ä The effects of T on total adipose tissue mass are apparently not very marked in normal adults or in aging men.

35. Illinois State University Testosterone ä Adipose tissue distribution is, however, probably regulated by T.

36. Illinois State University Testosterone ä T-deficiency has been suggested to be associated with centralization of body mass.

37. Illinois State University Testosterone ä This might be the explanation for well known tendency of aging men with decreased T-secretion to develop central fat accumulation.

38. Illinois State University Testosterone ä The cellular effects of T on adipocytes have been surprisingly little studied.

39. Illinois State University Testosterone ä Androgens are also produced by women, albeit in much smaller amounts.

40. Illinois State University Testosterone ä The effects of T on adipose tissue might be weaker, due to the lower concentrations of T.

41. Illinois State University Growth Hormone ä Pituitary growth hormone (GH) or somatotropin is obviously a major regulator of body composition.

42. Illinois State University Growth Hormone Effects on Body Composition: ä increases in muscle mass ä increases in extracellular water volume ä and a marked decrease in body fat.

43. Illinois State University Growth Hormone Effects on Cell Differentiation ä GH seems to promote the conversion of pre- adipocytes to fully differentiated adipocytes.

44. Illinois State University Growth Hormone ä It is unclear if this growth promoting effect of GH on pre-adipocytes is important in human beings after puberty, since effects of GH on pre-adipocyte conversion to adipocytes have not been observed indicating that these cells may be already “committed” in adult life.

45. Illinois State University Growth Hormone Effects on Adipose Tissue Metabolism: ä The long-term effects of GH on adipose tissue metabolism are undoubtedly a stimulation of lipolysis and inhibition of lipogenesis, reflected in the marked changes in body composition with GH excess or deficiency.

46. Illinois State University Growth Hormone Interactions with other hormones: ä The metabolic effects of GH are also dependent on insulin and glucocorticoids.

47. Illinois State University Growth Hormone ä GH has no growth promoting effect in the absence of insulin, and the metabolic effects of GH in adipose tissue also seem to be dependent on the presence of insulin.

48. Illinois State University Growth Hormone ä In human, GH secretion is dependent upon age and gonadal function. ä Another important observation is the consistent decrease in GH secretion in obesity.

49. Illinois State University Female Sex Hormones ä Female sex steroid hormone concentrations also regulate adipose tissue mass, although it is not clear whether these effects are direct or mediated via energy intake and/or expenditure.

50. Illinois State University Female Sex Hormones ä It is clear that these hormones affect body fat distribution in women. ä With menopause, VAT increases, but this is preventable by hormonal replacement therapy.

51. Illinois State University Increased Risk for Heart Disease with HRT ä The increased risk of heart attack or stroke, both in women with cardiovascular disease and in healthy women may be associated primarily with HRT using continuous combined oral estrogen and progestin (Prempro) or the daily use of an oral progestin such as Provera with estrogen.

52. Illinois State University Increased Risk for Heart Disease with HRT ä Recent research has suggested that the effects of estrogen on the cardiovascular system vary according to the mode of delivery of estrogen (oral versus transdermal). ä In addition, the effects of estrogen seem to be affected by the addition of a progestin, androgen, or a statin (cholesterol-lowering class of drugs). ä Much remains to be learned about these interactions and effects.

53. Illinois State University Female Sex Hormones ä Furthermore, the specific female enlargement of femoral subcutaneous adipocytes disappears with menopause.

54. Illinois State University Female Sex Hormones ä There is a considerable body of evidence suggesting that female sex steroid hormones exert important effects on adipose tissue distribution.

55. Illinois State University Interactions ä There are clearly interactions between the effects of the steroid and peptide hormones, insulin and GH, as well as the cathecholamines.

56. Illinois State University Interactions ä In addition, there are most likely interactions between the corticosteroid and sex steroid hormones.

57. Illinois State University Interactions ä Observations seem to indicate that cortisol and insulin are mainly promoting lipid accumulation and retention of triglycerides in the adipocytes, while T and GH oppose this effect.

58. Illinois State University Summary ä T, insulin, and GH have anabolic effects on muscle mass, while cortisol exerts opposite activities.

59. Illinois State University Summary ä Cortisol, in combination with insulin, seems to have positive effects on the balance of adipose tissue triglyceride accumulation and retention, mediated via stimulatory effects on lipid mobilization. ä These consequences are reversed by GH.

60. Illinois State University Summary ä Female sex steroid hormones and T probably have negative effects, amplified by GH, on adipose tissue triglyceride accumulation and retention. ä The reasons why are not clear.

61. Illinois State University Summary ä The redistribution of body fat stores might be a consequence of multiple endocrine abnormalities, perhaps leading directly, or via visceral fat accumulation, to the generation of metabolic risk factors and triggers for non-insulin dependent diabetes mellitus, cardiovascular disease, and stroke.