illinois state university ä hormonal influences on human body composition

Illinois State UniversityIllinois State University

Hormonal Influences on Human Body Hormonal Influences on Human Body CompositionComposition


HormonesHormones

Hormones exert major, determining effects Hormones exert major, determining effects on body composition.on body composition.


The Endocrine SystemThe Endocrine System

GlandGland HormoneHormone Target organ or tissue.Target organ or tissue.


HormonesHormones

Hormones can be classified as either Hormones can be classified as either steroidal or nonsteroidal. steroidal or nonsteroidal. SteroidSteroid hormones are lipid soluble, and most hormones are lipid soluble, and most

are formed from cholesterol.are formed from cholesterol. NonsteroidNonsteroid hormones are proteins, peptides, or hormones are proteins, peptides, or

amino acids.amino acids.


HormonesHormones

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


HormonesHormones

Steroid hormones pass through cell Steroid hormones pass through cell membranes and bind to receptors inside the membranes and bind to receptors inside the cell. cell. They use a mechanism called They use a mechanism called direct gene direct gene

activation activation to cause protein synthesis.to cause protein synthesis.


HormonesHormones

Non-steroidal hormones cannot enter cells Non-steroidal hormones cannot enter cells easily, so they bind to receptors on the cell easily, so they bind to receptors on the cell membrane. membrane. This activates a second messenger within the This activates a second messenger within the

cell which in turn can trigger numerous cellular cell which in turn can trigger numerous cellular processes.processes.


HormonesHormones

Secretion of most hormones is regulated by Secretion of most hormones is regulated by a a negative feedback systemnegative feedback system..


HormonesHormones

The number of receptors for a specific The number of receptors for a specific hormone can be altered to meet the body’s hormone can be altered to meet the body’s demands. demands.


HormonesHormones

Key point - the Key point - the pituitary gland pituitary gland was was once thought to be the once thought to be the master endocrine master endocrine gland solely in control gland solely in control of many other glands of many other glands and organs. and organs.


ControlControl

It is now recognized that the pituitary gland It is now recognized that the pituitary gland is largely controlled by the is largely controlled by the hypothalamushypothalamus..


HormonesHormones

Both Both peptide and steroid hormonespeptide and steroid hormones, alone or , alone or in combination, exert profound changes on in combination, exert profound changes on both the lean and fat compartments of body both the lean and fat compartments of body composition.composition.


HormonesHormones

The main physiological steroid hormones The main physiological steroid hormones affecting body composition include: affecting body composition include: cortisolcortisol, , testosteronetestosterone, and , and 17-beta-estradiol17-beta-estradiol..


HormonesHormones

The effects of these steroid hormones are The effects of these steroid hormones are dependent on the interactions of dependent on the interactions of GHGH and and insulininsulin..


Pituitary HormonesPituitary Hormones

Anterior LobeAnterior Lobe SomatotropinSomatotropin (hgH) - Impacts all cells of (hgH) - Impacts all cells of

the body. the body. Major role in maturation, protein synthesis, use Major role in maturation, protein synthesis, use

of fat, and CHO sparing.of fat, and CHO sparing.


Thyroid HormoneThyroid Hormone

Thyroxine and triiodothyronineThyroxine and triiodothyronine - Impact all - Impact all cells in the body. cells in the body. Increases rate of cellular metabolism, increases Increases rate of cellular metabolism, increases

heart rate and force of contraction.heart rate and force of contraction.


Adrenal HormonesAdrenal Hormones

MedullaMedulla EpinephrineEpinephrine - Impacts most cells of the - Impacts most cells of the

body. body. Mobilizes glycogen, increases skeletal muscle Mobilizes glycogen, increases skeletal muscle

blood flow, increases heart rate and blood flow, increases heart rate and contractility, increases oxygen consumption.contractility, increases oxygen consumption.



MedullaMedulla NorepinephrineNorepinephrine - impacts most cells of the - impacts most cells of the

body through vasoconstriction which body through vasoconstriction which increases blood flow, increases heart rate increases blood flow, increases heart rate and contractility, increases VOand contractility, increases VO22..



CortexCortex Glucocorticoids (Glucocorticoids (cortisolcortisol) - impacts most ) - impacts most

cells of the body. cells of the body. Controls metabolism of all fuels and has an Controls metabolism of all fuels and has an

anti-inflammatory action.anti-inflammatory action.



CortexCortex AndrogensAndrogens and and estrogensestrogens - impacts sex - impacts sex

organs. organs. Responsible for development of secondary Responsible for development of secondary

sexual characteristics.sexual characteristics.


Pancreatic HormonesPancreatic Hormones

InsulinInsulin - impacts all cells of the body. - impacts all cells of the body. Regulates blood glucose levels. Regulates blood glucose levels. Increases the utilization of glucose and the Increases the utilization of glucose and the

synthesis of fat.synthesis of fat.


Pancreatic HormonesPancreatic Hormones

Glucagon Glucagon - impacts all cells of the body. - impacts all cells of the body. Increases blood glucose levels and stimulates Increases blood glucose levels and stimulates

the breakdown of protein and fat.the breakdown of protein and fat.


Gonadal HormonesGonadal Hormones

TestesTestes TestosteroneTestosterone - affects sex organs and - affects sex organs and

muscles. muscles. Responsible for the development of male Responsible for the development of male

secondary sexual characteristics.secondary sexual characteristics.


Gonadal HormonesGonadal Hormones

OvariesOvaries EstrogenEstrogen - affects sex organs and adipose - affects sex organs and adipose

tissue. tissue. Responsible for the development of female Responsible for the development of female

secondary sexual characteristics.secondary sexual characteristics.


CortisolCortisol

Excess cortisol secretion causes wasting of Excess cortisol secretion causes wasting of lean body mass, particularly muscle.lean body mass, particularly muscle.


CortisolCortisol

The interactions of insulin become The interactions of insulin become important for the net effect of important for the net effect of glucocorticoids on muscle mass as well as glucocorticoids on muscle mass as well as on adipose tissue mass and distribution.on adipose tissue mass and distribution.


CortisolCortisol

In human adipose tissue, the acute short-In human adipose tissue, the acute short-term effects of cortisol seem to be term effects of cortisol seem to be essentially absent.essentially absent.


CortisolCortisol

In long-term (days) experiments under fully In long-term (days) experiments under fully controlled conditions, the effects are easier controlled conditions, the effects are easier to detect.to detect.


CortisolCortisol

In the presence of insulin, cortisol by itself In the presence of insulin, cortisol by itself has a rather weak inhibitory effect on has a rather weak inhibitory effect on cathecholamine-induced lipolysis, but cathecholamine-induced lipolysis, but cortisol induces a marked “permissive” cortisol induces a marked “permissive” effect by GH effect by GH on lipolysis.on lipolysis.

Result – decreased fat mass and muscle massResult – decreased fat mass and muscle mass


CortisolCortisol

The integrated effect of cortisol on lipolysis The integrated effect of cortisol on lipolysis would not be expected to increase lipolysis would not be expected to increase lipolysis because, with cortisol excess, GH secretion because, with cortisol excess, GH secretion is blunted.is blunted.


CortisolCortisol

Furthermore, insulin secretion is elevated, Furthermore, insulin secretion is elevated, with its consequences for lipid mobilization.with its consequences for lipid mobilization.


CortisolCortisol

The effects of glucocorticoids on adipose The effects of glucocorticoids on adipose tissue are regionally specific.tissue are regionally specific.


TestosteroneTestosterone

The effects of testosterone on lean body The effects of testosterone on lean body mass are well established, e.g., mass are well established, e.g., the elevation the elevation of muscle mass and reduction of adipose of muscle mass and reduction of adipose tissue storestissue stores..



The effects of T on total adipose tissue mass The effects of T on total adipose tissue mass are apparently not very marked in normal are apparently not very marked in normal adults or in aging men.adults or in aging men.



Adipose tissue distribution is, however, Adipose tissue distribution is, however, probably regulated by T.probably regulated by T.



T-deficiency has been suggested to be T-deficiency has been suggested to be associated with centralization of body mass.associated with centralization of body mass.



This might be the explanation for well This might be the explanation for well known tendency of aging men with known tendency of aging men with decreased T-secretion to develop central fat decreased T-secretion to develop central fat accumulation.accumulation.



The cellular effects of T on adipocytes have The cellular effects of T on adipocytes have been surprisingly little studied.been surprisingly little studied.



Androgens are also produced by women, Androgens are also produced by women, albeit in much smaller amounts.albeit in much smaller amounts.



The effects of T on adipose tissue might be The effects of T on adipose tissue might be weaker, due to the lower concentrations of weaker, due to the lower concentrations of T.T.


Growth HormoneGrowth Hormone

Pituitary Pituitary growth hormone growth hormone (GH) or (GH) or somatotropin is obviously a major regulator somatotropin is obviously a major regulator of body composition.of body composition.



Effects on Body Composition:Effects on Body Composition: increases in muscle massincreases in muscle mass increases in extracellular water volumeincreases in extracellular water volume and a marked decrease in body fat.and a marked decrease in body fat.



Effects on Cell DifferentiationEffects on Cell Differentiation GH seems to promote the conversion of GH seems to promote the conversion of

pre-adipocytes to fully differentiated pre-adipocytes to fully differentiated adipocytes.adipocytes.



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



Effects on Adipose Tissue Metabolism:Effects on Adipose Tissue Metabolism: The long-term effects of GH on adipose The long-term effects of GH on adipose

tissue metabolism are undoubtedly a tissue metabolism are undoubtedly a stimulation of lipolysis and inhibition of stimulation of lipolysis and inhibition of lipogenesislipogenesis, reflected in the marked changes , reflected in the marked changes in body composition with GH excess or in body composition with GH excess or deficiency.deficiency.



Interactions with other hormones:Interactions with other hormones: The metabolic effects of GH are also The metabolic effects of GH are also

dependent on insulin and glucocorticoids.dependent on insulin and glucocorticoids.



GH has no growth promoting effect in the GH has no growth promoting effect in the absence of insulin, and the metabolic effects absence of insulin, and the metabolic effects of GH in adipose tissue also seem to be of GH in adipose tissue also seem to be dependent on the presence of insulin.dependent on the presence of insulin.



In human, GH secretion is dependent upon In human, GH secretion is dependent upon age and gonadal function.age and gonadal function.

Another important observation is the Another important observation is the consistent decrease in GH secretion in consistent decrease in GH secretion in obesity.obesity.


Female Sex HormonesFemale Sex Hormones

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



It is clear that these hormones affect body It is clear that these hormones affect body fat distribution in women.fat distribution in women.

With menopause, VAT increases, but this is With menopause, VAT increases, but this is preventable by hormonal replacement preventable by hormonal replacement therapy.therapy.


Increased Risk for Heart Disease with HRTIncreased Risk for Heart Disease with HRT

The increased risk of heart attack or stroke, The increased risk of heart attack or stroke, both in women with cardiovascular disease both in women with cardiovascular disease and in healthy women may be associated and in healthy women may be associated primarily with HRT using continuous primarily with HRT using continuous combined oral estrogen and progestin combined oral estrogen and progestin (Prempro) or the daily use of an oral (Prempro) or the daily use of an oral progestin such as Provera with estrogen. progestin such as Provera with estrogen.


Increased Risk for Heart Disease with HRTIncreased Risk for Heart Disease with HRT

Recent research has suggested that the effects of Recent research has suggested that the effects of estrogen on the cardiovascular system vary estrogen on the cardiovascular system vary according to the mode of delivery of estrogen (oral according to the mode of delivery of estrogen (oral versus transdermal). versus transdermal).

In addition, the effects of estrogen seem to be In addition, the effects of estrogen seem to be affected by the addition of a progestin, androgen, affected by the addition of a progestin, androgen, or a statin (cholesterol-lowering class of drugs).or a statin (cholesterol-lowering class of drugs).

Much remains to be learned about these Much remains to be learned about these interactions and effects. interactions and effects.



Furthermore, the specific female Furthermore, the specific female enlargement of femoral subcutaneous enlargement of femoral subcutaneous adipocytes disappears with menopause.adipocytes disappears with menopause.



There is a considerable body of evidence There is a considerable body of evidence suggesting that female sex steroid hormones suggesting that female sex steroid hormones exert important effects on adipose tissue exert important effects on adipose tissue distribution.distribution.


InteractionsInteractions

There are clearly interactions between the There are clearly interactions between the effects of the steroid and peptide hormones, effects of the steroid and peptide hormones, insulin and GH, as well as the insulin and GH, as well as the cathecholamines.cathecholamines.



In addition, there are most likely In addition, there are most likely interactions between the corticosteroid and interactions between the corticosteroid and sex steroid hormones.sex steroid hormones.



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


SummarySummary

T, insulin, and GH have anabolic effects on T, insulin, and GH have anabolic effects on muscle mass, while cortisol exerts opposite muscle mass, while cortisol exerts opposite activities.activities.


SummarySummary

Cortisol, in combination with insulin, seems Cortisol, in combination with insulin, seems to have positive effects on the balance of to have positive effects on the balance of adipose tissue triglyceride accumulation adipose tissue triglyceride accumulation and retention, mediated via stimulatory and retention, mediated via stimulatory effects on lipid mobilization.effects on lipid mobilization.

These consequences are reversed by GH.These consequences are reversed by GH.


SummarySummary

Female sex steroid hormones and T Female sex steroid hormones and T probably have negative effects, amplified probably have negative effects, amplified by GH, on adipose tissue triglyceride by GH, on adipose tissue triglyceride accumulation and retention.accumulation and retention.

The reasons why are not clear.The reasons why are not clear.


SummarySummary

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

illinois state university ä hormonal influences on human body composition

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