Growth Hormone & Exercise Quiz

Hormonal Regulation of Metabolism in Exercise

• Hormones play a crucial role in regulating metabolism during exercise.
• Acute responses to exercise affect hormones like epinephrine, norepinephrine, cortisol, and glucose.
• Exercise's chronic adaptations also affect hormones.
• Major endocrine glands involved in metabolic regulation include the anterior pituitary, thyroid, adrenal, and pancreas.
• The hormones released by these glands specifically impact carbohydrate and fat metabolism during exercise.

Responses to Exercise

• Understanding acute and chronic responses to exercise is key to understanding the hormonal mechanisms involved.
• Acute responses are immediate reactions to exercise. Example hormonal changes, such as changes in epinephrine, norepinephrine, cortisol and glucose, as observed within 1-3 hours of exercise.
• Chronic adaptations are long-term changes in the body's response to exercise training over weeks, months or years, affecting various hormonal systems
• These responses are crucial to the hormones chapter to clarify what are the hormonal changes before and after an exercise and why are these changes important.

Acute Hormonal Responses

• Epinephrine, norepinephrine, glucagon, and cortisol levels rise sharply during exercise.
• Glucose levels increase.
• Changes in the graph display the hormonal response to exercise over a period of time, showing the different levels produced in hours or minutes.

Hormonal Regulation of Metabolism During Exercise

• Major endocrine glands control metabolic regulation: anterior pituitary, thyroid, adrenal, and pancreas.
• The hormones released from these glands influence metabolic rates and carbohydrate/fat metabolism during exercise.

Pituitary Hormones and Downstream Effects

• The pituitary gland is connected to the base of the hypothalamus.
• It's divided into three parts: anterior, intermediate, and posterior.
• The hypothalamus and pituitary hormones are involved in restoring homeostasis during and after training
• Exercise causes a stress response, detected by the hypothalamus, and triggers the pituitary to release hormones.

Anterior Pituitary Gland

• The anterior pituitary is controlled by the hypothalamus.
• It releases six specialized polypeptide hormones
• Hormones of interest, in response to hypothalamic releasing factors, are involved in stimulating various body functions
• Exercise causes stress, sensed by the hypothalamus to release hormones for homeostasis.

Anterior Pituitary Hormones

• The anterior pituitary releases six polypeptide hormones including releasing factors.
• Neural signals to the hypothalamus regulate the release of these factors in response to exercise, stress and anxiety.
• The hormones include various factors like growth hormone, gonadotropin hormones, adrenocorticotropic hormone (ACTH), and others.
• These hormones play various important roles in organs

Growth Hormone

• Growth hormone (GH) is an anabolic hormone released by the anterior pituitary
• GH promotes cell division, and tissue growth
• Resting/normal levels are higher in women.
• Exercise stimulates GH release because it's a potent anabolic agent.

Growth Hormone Actions

• GH stimulates protein synthesis, and promotes cell growth
• GH impacts skeletal effects
• GH contributes to the regulation of glucose, and promotes other metabolic responses to exercise

Growth Hormone and Tissue Synthesis

• Exercise increases growth hormone, with higher intensity/stress causing a greater increase.
• Exercise benefits muscle, bone, and connective tissue.
• Exercise preserves blood glucose levels.
• Exogenous HGH effects on muscle hypertrophy are not clear.
• There's some evidence it benefits connective tissue repair, yet its use in sports is now illegal.

Growth Hormone Regulation

• Trained and untrained people have similar increases in growth hormone.
• Untrained people maintain high GH levels for longer than those who have been trained in exercise.
• There are no chronic effects of exercise training on resting levels.
• High GH levels in adults can lead to acromegaly or gigantism

Insulin-Like Growth Factors

• IGFs mediate many GH effects, acting as primary stimulators of hypertrophy
• In response to GH, the liver synthesizes IGF-I and IGF-II peptides.
• IGFs are carried in blood attached to binding proteins, releasing to interact with receptors.
• They play a role in increasing protein synthesis, and amino acid transport.

Thyroid Gland

• The anterior pituitary releases thyrotropin (TSH).
• Exercise stimulates TSH release.
• TSH stimulates the thyroid gland to produce T3 and T4.
• T3 and T4 are amine hormones that bind to intracellular receptors.
• T3 and T4 activities and function include increasing metabolic rates, protein synthesis, and the function of mitochondria.

Adrenal Hormones

• The adrenal glands have two parts:
• Medulla releases catecholamines (epinephrine and norepinephrine) to prolong sympathetic responses.
• Cortex secretes steroid hormones (mineralocorticoids, glucocorticoids, and gonadocorticoids)

Catecholamines

• They're an essential part of the 'fight-or-flight' response.
• Catecholamines are amine hormones (epinephrine/norepinephrine), acting through 2nd messengers, enhancing various physiological responses like glycogenolysis and lipolysis.

Adrenal Medulla

• Releases catecholamines (primarily epinephrine).
• Exercise elevates sympathetic nervous system activity, leading to increased epinephrine and norepinephrine release.

Catecholamines and Exercise

• Catecholamine levels rise sharply with the onset of exercise, correlating with exercise intensity.
• Levels decrease during prolonged, moderate-intensity exercise.
• Exercise training diminishes the body's catecholamine response overtime.

Adrenergic Receptors

• Receptor types determine cells' response to hormones.
• Alpha (α) and beta (β) adrenergic receptors are two classes that influence the body's response.
• Alpha receptors primarily cause vasoconstriction.
• Beta receptors lead to vasodilation, bronchodilation, and increased heart rate.

Adrenal Cortex

• The adrenal cortex releases corticosteroids. The most important glucocorticoid is cortisol, activating gluconeogenesis, a key function to maintain blood glucose.
• Cortisol acts as an anti-inflammatory substance and suppresses anti-immune reactions.

Gonadocorticoids

• The adrenal cortex releases small amounts of gonadocorticoids.
• The most important one is dehydroepiandrosterone (DHEA).
• These have similar effects to testosterone, estrogen, and progesterone.

Gonadal Hormones

• Testosterone is the main androgen. It plays an important role in the development of male secondary characteristics.
• Estrogen helps to regulate ovulation and menstrual cycles, as well as physiological adjustments during pregnancy.
• Progesterone regulates the reproductive cycle, uterine smooth muscle action, and lactation.

Testosterone

• The primary androgen hormone that interacts with skeletal muscle tissue.
• Intense or high volume exercises can lead to increases in serum testosterone.
• Exercise in the later part of the day is more effective for increasing overall testosterone in men.
• Women have lower concentrations without much variation throughout the day.

Serum Testosterone Responses to Exercise

• Male and females have different serum responses to exercise.
• There are different protocols for exercise intensity between males and females.
• Both protocols can effectively increase serum levels of testosterone

Prohormones

• Prohormones are precursors to testosterone.
• There is limited evidence supporting notable ergogenic improvements from prohormone use.
• Prohormones could have adverse side effects similar to anabolic steroids.
• Example prohormones: androstenedione and DHEA.

Lipid Metabolism

• Lipolysis, the breakdown of fats into fatty acids, is important during prolonged endurance exercise when glycogen stores are depleted.
• Hormone-sensitive lipase (HSL) is the key enzyme, stimulated by epinephrine, norepinephrine, and growth hormone.

Regulation of Fat Metabolism During Exercise

• Fat mobilization and metabolism are critical for endurance exercise.
• Triglycerides are broken down into glycerol and fatty acids, then transported to muscles for energy.
• Lipolysis is stimulated by cortisol, epinephrine, norepinephrine, and growth hormone.

Regulation of Fat Metabolism During Exercise

• Lipolysis is stimulated by epinephrine, norepinephrine, growth hormone, and to a lesser extent, cortisol, all via cAMP pathway.
• This pathway activates Hormone-Sensitive Lipase (HSL), which breaks triglycerides down into glycerol and free fatty acids for use in energy production.

Test your knowledge about the role of growth hormone in the body, its stimulation triggers, and its effects on muscle development. This quiz also explores how exercise influences growth hormone levels in both trained and sedentary individuals. Perfect for students in physiology or health sciences.