Growth Hormone Functions and Effects
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Questions and Answers

Which of the following factors directly inhibit the secretion of growth hormone?

  • Hypoglycemia
  • Protein meals
  • Stress
  • Free fatty acids (correct)

    • What is the primary effect of growth hormone on glucose metabolism?

  • Increases glucose production and gluconeogenesis (correct)
  • Promotes glycogen synthesis
  • Decreases glucose production
  • Increases insulin sensitivity

    • Which hormone directly mimics the action of insulin, promoting protein synthesis and anti-lipolytic activity?

  • Epinephrine
  • IGF-1 (correct)
  • Cortisol
  • Glucagon

    • During an extended fasting state, which hormone exhibits a synergistic effect with epinephrine and glucagon, enhancing their actions?

    <p>Cortisol (B)</p> Signup and view all the answers

    In the fasting state, which hormone inhibits insulin secretion, contributing to the mobilization of stored fuel?

    <p>Growth Hormone (C)</p> Signup and view all the answers

    Which of these hormones contribute to a net catabolic effect on the body? (Select all that apply.)

    <p>Cortisol (A), Glucagon (C), Epinephrine (E)</p> Signup and view all the answers

    Which of the following hormones promotes glucose, protein, and fat storage in the fed state, favoring an anabolic state?

    <p>Insulin (C)</p> Signup and view all the answers

    During starvation, what effect does ketone production have on glucagon secretion?

    <p>Suppresses glucagon secretion (D)</p> Signup and view all the answers

    In the fed state, which hormone is elevated due to increased amino acid levels and contributes to preventing hypoglycemia?

    <p>Glucagon (D)</p> Signup and view all the answers

    Which of the following is a factor that inhibits glucagon secretion?

    <p>Free fatty acids (B)</p> Signup and view all the answers

    What is the primary role of glucagon in maintaining blood glucose levels?

    <p>Increasing glucose production by the liver (D)</p> Signup and view all the answers

    Which of the following hormones also stimulates lipolysis, similar to glucagon?

    <p>Epinephrine (D)</p> Signup and view all the answers

    What is the main difference between glucagon and epinephrine in terms of their action on glycogen breakdown?

    <p>Glucagon acts only in the liver, while epinephrine acts in both liver and muscle (D)</p> Signup and view all the answers

    Which of the following is a direct effect of cortisol on glucose metabolism?

    <p>Enhancing the effects of glucagon and epinephrine (C)</p> Signup and view all the answers

    Which of these conditions can be a consequence of cortisol deficiency?

    <p>Hypoglycemia (C)</p> Signup and view all the answers

    Which of the following is a direct action of glucagon on the liver?

    <p>Increased glucose output (A)</p> Signup and view all the answers

    How does glucagon contribute to the maintenance of blood glucose levels during fasting?

    <p>By stimulating glucose uptake by muscle (A)</p> Signup and view all the answers

    Which of the following is a typical symptom of Cushing's Syndrome, a condition of prolonged cortisol excess?

    <p>Hypoglycemia (A)</p> Signup and view all the answers

    What is the main function of protein kinases in mediating hormone signaling?

    <p>To activate or inactivate specific intracellular proteins (B)</p> Signup and view all the answers

    How does epinephrine influence glucose metabolism in skeletal muscle?

    <p>Stimulating glycogen breakdown (B)</p> Signup and view all the answers

    Why is glucagon often administered to patients with hypoglycemia?

    <p>To increase glucose production in the liver (D)</p> Signup and view all the answers

    Which of the following accurately describes the effects of both glucagon and epinephrine on glucose metabolism?

    <p>Both stimulate glycogenolysis (C)</p> Signup and view all the answers

    Which of these hormones is primarily responsible for maintaining blood glucose levels during prolonged fasting?

    <p>Cortisol (C)</p> Signup and view all the answers

    What is the primary effect of cortisol on the liver?

    <p>Enhancing the effects of other hormones involved in glucose synthesis (B)</p> Signup and view all the answers

    Flashcards

    Growth Hormone (GH)

    A hormone that stimulates growth, cell reproduction, and regeneration in the body.

    Insulin and Growth Hormone relationship

    Both insulin and GH promote protein synthesis, but only insulin promotes fat and glycogen synthesis.

    IGF-1

    Insulin-like Growth Factor 1, mimics insulin action and promotes protein synthesis and growth effects from GH.

    Factors stimulating GH secretion

    Conditions that increase GH release include hypoglycemia, stress, exercise, and sleep.

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    Catabolic Hormones

    Hormones like glucagon, epinephrine, and cortisol that promote breakdown of body tissues.

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    Fed State

    The metabolic state after eating when nutrients are absorbed and stored.

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    Insulin Function

    Hormone released to promote storage of glucose, proteins, and fats after eating.

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    Fasting State

    Metabolic state where the body mobilizes stored fuel due to low glucose levels.

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    Cortisol Role

    Stress hormone released during low glucose conditions to aid energy mobilization.

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    Ketone Production

    Occurs during starvation; ketones become an alternative fuel source when glucose is low.

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    Glucagon

    A hormone secreted by alpha cells of the pancreas to raise blood glucose levels during fasting.

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    Gluconeogenesis

    The process of synthesizing glucose from non-carbohydrate sources, primarily in the liver.

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    Glycogenolysis

    The breakdown of glycogen into glucose, primarily occurring in the liver.

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    Lipolysis

    The breakdown of triglycerides into glycerol and free fatty acids for energy.

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    Stimulators of Glucagon Secretion

    Factors that trigger glucagon release, such as low glucose, amino acids, and fasting.

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    Inhibitors of Glucagon Secretion

    Factors that decrease glucagon release, like high glucose and insulin.

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    Epinephrine

    A hormone produced by the adrenal medulla that increases blood glucose by promoting glycogenolysis and gluconeogenesis.

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    Cortisol

    A glucocorticoid hormone that regulates metabolism, stress response, and blood pressure.

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    Combined Catabolic Effects

    The synergistic actions of glucagon, epinephrine, and cortisol to increase blood glucose during fasting.

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    Cushing's Syndrome

    A condition of excess cortisol leading to hyperglycemia, obesity, and insulin resistance.

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    Addison's Disease

    A disorder due to cortisol deficiency, causing hypoglycemia and low blood pressure.

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    Hormone-sensitive Lipase

    An enzyme activated by glucagon and epinephrine to stimulate lipolysis.

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    Receptors for Epinephrine

    Different types of receptors (alpha and beta) that mediate epinephrine effects in various tissues.

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    Ketogenesis

    The process of producing ketones from fatty acids for energy when glucose is low.

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    Protein Synthesis Inhibition by Glucocorticoids

    Cortisol impairs protein synthesis in muscle leading to muscle atrophy.

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    Study Notes

    Growth Hormone (GH)

    • GH has diverse effects, including sodium retention, decreased insulin sensitivity, lipolysis (fat breakdown), protein synthesis (anabolic), bone growth stimulation, and IGF-1 secretion stimulation.
    • GH and insulin both promote protein synthesis, making them anabolic hormones. Insulin also promotes triglyceride and glycogen synthesis, unlike GH.
    • IGF-1 has insulin-like activity, anti-lipolytic activity, and promotes protein synthesis.
    • GH's direct actions stimulate protein synthesis. Indirectly, it promotes protein synthesis via IGF-1 and stimulates bone growth. It also increases muscle protein synthesis, liver glucose production and gluconeogenesis, decreases insulin action on glucose uptake, and increases the action of lipolytic agents (epinephrine and glucagon). This leads to increased free fatty acid and ketone levels.
    • Factors stimulating GH secretion include hypoglycemia, stress, exercise, protein meals (amino acids like arginine), sleep onset, androgens, and estrogens.
    • GH levels are highest during adolescence and lower in adulthood and old age.
    • Low GH leads to reduced lean body mass, smaller protein mass, and reduced bone mass.
    • Factors inhibiting GH include free fatty acids, cortisol, glucose, REM sleep, and IGF-1.
    • In a 16-year-old boy, GH simultaneously increases protein synthesis and glucose production.

    Catabolic Hormones

    • Catabolic hormones (glucagon, epinephrine, and cortisol) have a clear catabolic function.

    Glucagon

    • Secreted by alpha cells in the pancreas in response to low blood glucose (e.g., fasting).
    • Actions:
      • Liver: stimulates gluconeogenesis (glucose synthesis from amino acids) and glycogenolysis (glycogen breakdown).
      • Fat tissue: stimulates lipolysis (triglyceride breakdown).
    • Glucagon synthesis starts with a large precursor, then undergoes post-translational processing. The products—glucagon, MPGF, GPRP, GRPP—vary based on the cells and enzymes involved. Intestine cells produce GLP-1 and other molecules.
    • Summary of Glucagon Actions:
      • Stimulates liver glycogenolysis (not muscle).
      • Stimulates glucose synthesis through gluconeogenesis.
      • Stimulates lipolysis.
      • Generates ketones.
      • Mobilizes energy stores.
    • Glucagon increases glucose output through various mechanisms including the activation of protein kinase A, glycogen breakdown, and inhibition of glucose metabolism.
    • Glucagon increases lipolysis via hormone-sensitive lipase activation, enhancing triglyceride breakdown to glycerol and free fatty acids.
    • Factors stimulating glucagon secretion include amino acids, GI hormones (CCK, gastrin), cortisol, exercise, infection, and fasting.
    • Factors inhibiting glucagon secretion include glucose, free fatty acids, ketones, secretin, insulin, somatostatin, and alpha/beta-adrenergic stimulation

    Epinephrine

    • Produced by the adrenal medulla.
    • Actions:
      • Glycogenolysis: breaks down glycogen in liver and muscle.
      • Stimulates gluconeogenesis.
      • Decreases glucose uptake.
      • Stimulates lipolysis (via hormone-sensitive lipase).
      • Stimulates ketogenesis.
      • Mobilizes energy stores.
    • Factors stimulating epinephrine release include anxiety, fear, pain, hypoglycemia, hypotension, hypovolemia, hypothermia, hypoxia, and exercise.
    • Epinephrine's effects vary by receptor type. This means a single receptor can have a different impact on different tissues.

    Cortisol

    • Factors Stimulating Cortisol Secretion: Pain, low glucose, low blood pressure, low volume, low temperature, low oxygen, exercise
    • Actions:
      • Liver: Enhances norepinephrine and glucagon actions on gluconeogenesis for more glucose production.
      • Adipose Tissue: Promotes lipolysis.
      • Skeletal Muscle: Facilitates protein breakdown and glycogenolysis.
    • Cortisol, a glucocorticoid, inhibits calcium uptake in the GI tract, bone formation, collagen synthesis, and IGF-1's actions on bone and muscle.
    • It aids in fetal organ maturation (liver, lungs, GI tract).
    • Glucocorticoid net effects: inhibit growth, decrease stature in children, increase osteoporosis and muscle atrophy in adults.

    Combined Catabolic Effects (Glucagon, Epinephrine, Cortisol) During Fasting

    • Hypoglycemia triggers glucagon and epinephrine release.
    • Glucagon and epinephrine stimulate gluconeogenesis and glycogenolysis to increase glucose production.
    • Cortisol enhances glucagon and epinephrine's effects by producing enzymes. Cortisol's effects are slower due to its steroid nature. Cortisol also increases liver glycogen storage, breaks down skeletal muscle protein, and has a longer-term effect.

    Disease States (Cortisol Imbalance)

    • Cortisol Excess (Cushing's Syndrome): Hyperglycemia, insulin resistance, protein wasting, poor wound healing, truncal obesity, hypertension, hypernatremia, hypokalemia, infections, decreased inflammatory responses, euphoria.
    • Cortisol Deficiency (Addison's Disease): Hypoglycemia, low blood pressure, poor response to angiotensin II, low volume, low sodium, high potassium, depression, skin hyperpigmentation.

    Hormonal Changes in Different Metabolic States

    • Summarizes hormonal changes like glucose, insulin, glucagon, epinephrine, GH, and cortisol during fed, fasting, extended fasting, and starvation states. Highlights the net effects of each state (e.g., fed = absorption/storage, fasting = fuel mobilization).

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    Description

    Explore the diverse effects of Growth Hormone (GH) on metabolism, protein synthesis, and bone growth. This quiz covers the mechanisms of GH and its interaction with insulin and IGF-1, along with factors that stimulate GH secretion. Test your understanding of how GH influences various physiological processes.

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