Growth Hormone Physiology
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Questions and Answers

What is the molecular weight of growth hormone?

  • 25,000
  • 18,000
  • 20,000
  • 21,500 (correct)

    • Which of the following is NOT a physiological effect of growth hormone?

  • Decreasing glucose utilization
  • Promoting mitosis
  • Increasing cell size
  • Reducing muscle mass (correct)

    • How does growth hormone primarily affect protein metabolism?

  • By promoting amino acid transport (correct)
  • By increasing fatty acid transport
  • By accelerating protein catabolism
  • By inhibiting RNA translation

    • What role does GH play in relation to chondrocytes during bone development?

    <p>It stimulates the differentiation of chondrocytes into osteogenic cells.</p> Signup and view all the answers

    What is the half-life of circulating growth hormone?

    <p>20 minutes</p> Signup and view all the answers

    Which mechanism allows growth hormone to promote an anabolic effect on proteins?

    <p>Increase in insulin release</p> Signup and view all the answers

    Which factor is primarily responsible for the bone length increase until epiphyseal fusion?

    <p>Growth hormone</p> Signup and view all the answers

    What effect does growth hormone have on fat metabolism?

    <p>Mobilizes fats from adipose tissue</p> Signup and view all the answers

    How does somatomedin C exert its effects on bone and protein metabolism?

    <p>Through the second messenger cyclic AMP.</p> Signup and view all the answers

    What is a major effect of growth hormone on carbohydrate metabolism?

    <p>Increases glycogen deposition in cells</p> Signup and view all the answers

    Which of the following effects does GH have on electrolyte balance in the body?

    <p>It decreases the elimination of electrolytes from the body.</p> Signup and view all the answers

    Which organ is primarily responsible for the degradation of growth hormone?

    <p>Liver</p> Signup and view all the answers

    What is the primary molecular weight classification of somatomedin C?

    <p>Approximately 7,500</p> Signup and view all the answers

    Which type of growth does GH primarily support throughout life after the epiphyseal fusion?

    <p>Thickening of membranous bones</p> Signup and view all the answers

    What triggers the secretion of somatomedin in the liver?

    <p>Growth hormone</p> Signup and view all the answers

    How does GH influence muscle mass development?

    <p>Through sarcomere hypertrophy.</p> Signup and view all the answers

    What condition results in atrophy of the adrenal cortex and sensitivity to stress?

    <p>Pituitary insufficiency</p> Signup and view all the answers

    Which hormone is primarily responsible for stimulating growth and influencing metabolism during stress?

    <p>Growth hormone</p> Signup and view all the answers

    What is a key diagnostic test used to determine growth hormone deficiency?

    <p>GH stimulation tests</p> Signup and view all the answers

    Which of the following hormones does the anterior lobe of the pituitary primarily secrete?

    <p>Prolactin</p> Signup and view all the answers

    What effect does growth hormone have on IGF-I production?

    <p>Stimulates IGF-I production</p> Signup and view all the answers

    Which factor is NOT directly regulated by growth hormone?

    <p>Thyroid function</p> Signup and view all the answers

    Which condition can cause pituitary insufficiency in women?

    <p>Postpartum hemorrhage</p> Signup and view all the answers

    How is the secretion of growth hormone primarily regulated?

    <p>Feedback inhibition</p> Signup and view all the answers

    Which hormone primarily inhibits growth hormone secretion?

    <p>Growth hormone-inhibitory hormone (GHIH)</p> Signup and view all the answers

    What factor does NOT stimulate the secretion of growth hormone?

    <p>Hyperglycemia</p> Signup and view all the answers

    In which stages of sleep does the majority of growth hormone secretion occur?

    <p>Stage 3 and 4</p> Signup and view all the answers

    What condition results from hypersecretion of growth hormone during childhood?

    <p>Gigantism</p> Signup and view all the answers

    Which of the following accurately describes the role of somatomedins?

    <p>They execute the actions of growth hormone.</p> Signup and view all the answers

    Which hormone increases the release of GHRH from the hypothalamus?

    <p>Growth hormone-releasing polypeptide (GHRP)</p> Signup and view all the answers

    What condition can result from prolonged hypersecretion of growth hormone, characterized by disproportionately long limbs?

    <p>Gigantism</p> Signup and view all the answers

    Which factor does NOT play a role in the regulation of GH secretion?

    <p>Blood pressure levels</p> Signup and view all the answers

    What is the underlying cause of acromegaly in adults?

    <p>Tumor of acidophil cells in the anterior pituitary</p> Signup and view all the answers

    Which of the following is NOT a common sign or symptom of acromegaly?

    <p>Short stature</p> Signup and view all the answers

    What treatment options can be used to block GH secretion in acromegaly?

    <p>Somatostatin agonists and bromocriptine</p> Signup and view all the answers

    What characterizes dwarfism compared to acromegaly?

    <p>It results from reduced GH secretion during childhood</p> Signup and view all the answers

    Which condition is associated with dwarfism due to a compression of GH-secreting cells?

    <p>Tumor of chromophobes</p> Signup and view all the answers

    What is a potential complication of acromegaly related to nerve compression?

    <p>Carpal tunnel syndrome</p> Signup and view all the answers

    Which of the following is true about the growth patterns in individuals with dwarfism?

    <p>Growth is stunted but proportions are nearly normal</p> Signup and view all the answers

    Which of these is NOT typically affected by acromegaly?

    <p>Stunted growth</p> Signup and view all the answers

    Study Notes

    Growth Hormone (GH)

    • Secreted by somatotropes (acidophilic cells) in the anterior pituitary
    • Polypeptide with 191 amino acids, molecular weight of 21,500
    • Basal levels in adults are typically less than 3 ng/mL, and in children/adolescents, about 6 ng/mL
    • Transported in blood by GH-binding proteins (GHBPs)
    • Half-life of circulating GH is ~20 minutes
    • Degraded in the liver and kidneys

    Action of Growth Hormone

    • Promotes general body growth by increasing cell size (hypertrophy) and cell number (mitosis)
    • Plays a role in the differentiation of specific cell types, including bone and muscle cells

    Physiological Effects of GH

    Effect on Metabolism

    • Increases protein synthesis
    • Mobilizes lipids
    • Conserves carbohydrates
    On Protein Metabolism
    • Increases amino acid transport across cell membranes
    • Enhances RNA translation
    • Increases DNA to RNA transcription
    • Decreases protein catabolism
    • Promotes protein anabolism indirectly (insulin release)
    On Fat Metabolism
    • Mobilizes fats from adipose tissue
    • Provides energy, thus sparing proteins
    • High levels can lead to ketone production
    On Carbohydrate Metabolism
    • Conserves glucose (decreases peripheral utilization)
    • Increases glycogen deposition in cells
    • Decreases glucose uptake by cells (diabetogenic effect - high levels will increase blood glucose significantly)
    • Will cause continuous stimulation of the islets of Langerhans, increasing insulin production

    Effects on Bone

    • Promotes differentiation and development in the embryonic stage
    • Increases bone growth in length and thickness
    • Stimulates protein synthesis and deposition by chondrocytes and osteogenic cells
    • Enhances chondrocyte and osteogenic cell multiplication
    • Converts chondrocytes to osteogenic cells

    Effects on Electrolytes

    • Decreases electrolyte elimination from the body
    • Directs electrolytes to tissues for growth
    • Increases muscle mass (hypertrophy of sarcomeres)
    • Stimulates growth of internal organs (excluding brain)
    • Plays a role in homeostasis
    • Stimulates the immune system
    • Increases deiodination of T4 to T3 (thyroxin)

    Regulation of GH Secretion

    • Hypothalamus plays a key role via GHRH (growth hormone releasing hormone), GHRP (growth hormone releasing polypeptide), and GHIH/somatostatin
    • These hormones travel through hypothalamo-hypophyseal portal blood vessels to the anterior pituitary
    • Hypoglycemia, fasting, starvation, exercise, sleep (initial stages), and stress can stimulate GH secretion
    • Hyperglycemia, increased free fatty acids, and later stages of sleep inhibit GH secretion

    Somatomedins (Insulin-like Growth Factors: IGFs)

    • Polypeptides secreted by the liver in response to GH
    • Act through the second messenger cyclic AMP
    • Two types: IGF-I (somatomedin C) and IGF-II; IGF-I plays a major role in bone and protein metabolism and lasts longer (20 hours), IGF-II is important for fetal growth

    Gigantism and Acromegaly

    • Gigantism: Hypersecretion of GH in childhood (before epiphyseal fusion)
    • Acromegaly: Hypersecretion of GH in adulthood (after epiphyseal fusion)
    • Symptoms include abnormal bone growth, increased organ size, etc

    Dwarfism

    • Hypoactivity of anterior pituitary, characterized by stunted growth
    • Potential causes include tumors (chromophobe), panhypopituitarism (reduced secretion of multiple pituitary hormones).

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    Growth Hormone (GH) PDF

    Description

    Explore the role and physiological effects of Growth Hormone (GH) in the human body. This quiz covers its secretion, metabolic impacts, and actions on protein and cell growth. Test your knowledge on the intricacies of GH and its significance in overall growth and development.

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