lecture 3 exercise endocrinology

Types of Hormones

• Steroid Hormones:– Structure similar to cholesterol– Can pass through cell membranes– Direct gene activation

• Non-steroid Hormones:– Protein/peptide or amino acid-derived– Cannot pass through cell membrane– Second messenger activation

Steroid Hormones

Steroid Hormones

• Proteins formed from mRNA may be:– Enzymes– Structural Proteins– Regulatory Proteins

• Includes:– Cortisol– Aldosterone– Estrogen/Progesterone/Testosterone

Non-steroid Hormones

Non-steroid Hormones

• Second Messengers (cAMP) can:– Activate cellular enzymes– Change membrane permeability– Promote protein synthesis– Change cellular metabolism– Stimulate cellular secretions

• Includes:– Thyroid Hormones– Epinephrine/Norepinephrine

Overview• Hormones that mediate specific actions

during exercise:–Regulation of Glucose Metabolism–Regulation of Fat Metabolism–Regulation of Blood Plasma

Regulation of Glucose Metabolism

• Controlled by Five Hormones:– Insulin (Rest Only)– Glucagon– Epinephrine– Norepinephrine– Cortisol

• During Exercise Blood Glucose is affected by three factors:– Liver release of glucose– Muscle uptake of glucose– Dietary intake of glucose

Glucagon

• Secretion Site: Pancreas ( cells)

• Action: Cause liver glycogen breakdown and glucose release to blood

• Exercise Response: Positively correlated to exercise intensity

• Effect of Chronic Exercise: at given intensity compared to untrained individual

Epinephrine and Norepinephrine

• Secretion Site: Adrenal Medulla and SNS

• Action: Works with Glucagon

• Exercise Response: Positively correlated to exercise intensity (intensity >50-75% of max effort)

• Effect of Chronic Exercise: at given intensity compared to untrained individual

Cortisol

• Secretion Site: Adrenal Cortex

• Action: Increase in Protein Catabolism, Increase blood amino acids for gluconeogenesis (making glucose from other substrates)

• Exercise Response: Positively correlated to exercise intensity (>80% max effort)

• Effect of Chronic Exercise: Slight at given intensity compared to untrained individual

Short Duration Exercise

High intensity = Greater catecholamine release = Greater release of glucose from liver

40-50% increase in blood glucose

Replenishes muscle glycogen stores

Long Duration Exercise

• Glucose production = demand

• Liver glycogen stores are a limiting factor

• Blood glucose concentration may decrease

• Glucagon/Cortisol gluconeogenesis

• CHO intake beneficial

Blood Glucose Exercise Response

Exercise Duration (min)

Glucagon

Cortisol

15 60 90

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Blood Glucose

Insulin

• Secretion Site: Pancreas ( cells)

• Action: Glucose uptake by muscle at rest, regulating blood glucose concentration

• Exercise Response: Not released during exercise; receptors more sensitive, thus less insulin required

• Effect of Chronic Exercise: No exercise response

Insulin, Blood Glucose, & Exercise

Exercise Duration (min)30 60 90

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Blood Glucose

Insulin

Regulation of Fat Metabolism• Controlled by Five Hormones:

– (Insulin)– Cortisol– Epinephrine– Norepinephrine– Growth Hormone

• Fat Metabolism is needed– When exercise depletes glycogen stores (long

duration exercise)– When diet depletes glycogen stores (fasting, low

CHO dieting, etc.)

Cortisol

• Secretion Site: Adrenal Cortex

• Action: Increase Liver Gluconeogenesis, blood Free Fatty Acids

• Exercise Response: Positively correlated to exercise intensity, but only acts during first 30-45 minutes

• Effect of Chronic Exercise: Slight at given intensity compared to untrained individual

Epinephrine and Norepinephrine

• Secretion Site: Adrenal Medulla and SNS

• Action: Activates hormone sensitive lipase, works with glucagon

• Exercise Response: Positively correlated to exercise intensity (intensity >50-75% of max effort)

• Effect of Chronic Exercise: at given intensity compared to untrained individual

Growth Hormone

• Secretion Site: Anterior Pituitary Gland

• Action: Maintains cortisol induced activation of hormone sensitive lipase

• Exercise Response: Positively correlated to exercise intensity

• Effect of Chronic Exercise: at given intensity compared to untrained individual

Fat Metabolism during Exercise

Exercise Duration (min)30 60 90

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Blood FFA

Cortisol

Growth Hormone

E + NE

Glycogen

Regulation of Blood Plasma

• Controlled by Five Hormones:– Aldosterone– Renin– Angiotensin I– Angiotensin II– Antidiuretic Hormone (ADH)

• Maintenance of Blood and Blood Plasma– Maintain blood supply to active tissue– Provide fluid for the production of sweat– Increased oxygen carrying capacity

Aldosterone

• Secretion Site: Adrenal Cortex

• Action: Increased Na+ and water reabsorption in the kidneys

• Exercise Response: Positively correlated to change in plasma volume

• Effect of Chronic Exercise: No effect

Signal for Aldosterone Release

1. Kidneys sense drop in blood pressure (due to decrease in plasma volume)

2. Kidneys release Renin

3. Renin is transformed to Angiotensin I, which is transformed into Angiotensin II

4. Angiotensin II stimulates Aldosterone release from the Adrenal Cortex

Renin-Angiotensin-Aldosterone

ADH

• Secretion Site: Posterior Pituitary Gland

• Action: Increases water reabsorption in the kidneys

• Exercise Response: Positively correlated to increase blood concentration (hemoconcentration)

• Effect of Chronic Exercise: at given intensity compared to untrained individual

ADH

Maintenance of Blood Plasma

Exercise Duration (min)30 60 90

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Plasma Volume

Aldosterone

-15%

ADH