Growth Hormone Production and Regulation
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Questions and Answers

What hormone stimulates the release of growth hormone (GH)?

  • Ghrelin (correct)
  • Insulin
  • Leptin
  • Somatostatin

At what stage of life is the secretion of growth hormone typically at its peak?

  • Infancy
  • Adulthood
  • Puberty (correct)
  • Elderly

Which of the following hormones negatively regulates the production of growth hormone?

  • Growth hormone releasing hormone
  • Ghrelin
  • Insulin-like growth factor 1 (IGF1) (correct)
  • Adrenocorticotropic hormone

What condition results from abnormal hyper-secretion of growth hormone in childhood?

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

What role does Insulin Growth Factor 1 (IGF-1) play in the action of growth hormone (GH)?

<p>It acts as a second messenger for GH effects. (A)</p> Signup and view all the answers

What is the role of Janus Kinase 2 (JAK2) in the GH signaling pathway?

<p>Phosphorylates downstream targets (D)</p> Signup and view all the answers

In which condition is mecasermin particularly beneficial?

<p>When there is high GH but dysfunctional receptors. (B)</p> Signup and view all the answers

What major action does growth hormone (GH) have related to body composition?

<p>Promotes muscle mass maintenance (C)</p> Signup and view all the answers

Which process occurs when GH interacts with its receptors?

<p>Phosphorylation of STAT5 (C)</p> Signup and view all the answers

What is the primary clinical effect of Tesamorelin?

<p>Reduction of visceral fat accumulation. (A)</p> Signup and view all the answers

What is a potential side effect of using mecasermin?

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

What physiological role does growth hormone (GH) play during childhood?

<p>Promotes postnatal longitudinal growth of the bones (B)</p> Signup and view all the answers

What role does octreotide play in the treatment of GH-related conditions?

<p>Acts as a somatostatin analogue to inhibit GH secretion. (C)</p> Signup and view all the answers

What is pegvisomant used for?

<p>To inhibit growth hormone receptor activity. (D)</p> Signup and view all the answers

What is the primary reason for administering GH releasing hormones?

<p>To induce the natural release of GH. (B)</p> Signup and view all the answers

Which scenario illustrates a condition of GH deficiency?

<p>Short stature in children due to receptor mutations. (D)</p> Signup and view all the answers

Flashcards

Growth Hormone (GH) interaction with Insulin Growth Factor 1 (IGF-1)

GH stimulates the production of IGF-1, which then has effects similar to GH, influencing various tissues, including liver, bone, fat (adipocytes), and muscle.

Mecasermin

Recombinant human IGF-1, used to treat GH deficiency where receptors don't work properly, even with high GH levels.

GH Deficiency

Lower-than-normal level of growth hormone.Can result in short stature in children.

Somatotropin

A growth hormone analogue, used for replacement therapy in GH deficiency cases.

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Octreotide

A somatostatin analogue used to reduce excessive growth hormone secretion.

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Pegvisomant

Growth hormone receptor antagonist, used to block the effects of excess GH.

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Tesamorelin

A GH-releasing hormone, enhancing GH and IGF-1 levels, primarily to reduce visceral fat.

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Hypoglycemia (side effect of Mecasermin)

Low blood sugar, a potential adverse effect of Mecasermin administration.

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GH production regulation

GH release is controlled by the hypothalamus through GH releasing hormone (GHRH) and somatostatin (SST). Ghrelin, from the stomach, also increases GH production.

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GH secretion patterns

GH levels are highest in infancy and puberty, decreasing in adulthood. Secretion is pulsatile (in bursts), peaking during sleep, and influenced by GHRH, Ghrelin, somatostatin, GH itself and IGF-1.

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GH action

GH stimulates growth, particularly bone growth, and also affects metabolism, influencing muscle mass, fat, and the immune system; also influencing the nervous system and heart.

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GH receptor mechanism

GH binds to a cell-surface receptor (GHR), activating a signaling pathway involving JAK2, STAT5, and gene transcription

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Gigantism

Excessive GH secretion in childhood, leading to abnormally high longitudinal bone growth.

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Acromegaly

Excessive GH secretion in adulthood causing enlargement of bones and soft tissues, especially in hands, feet, and face.

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IGF-1

Insulin-like growth factor 1, a hormone produced in response to GH that is pivotal in mediating GH actions on tissues.

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Study Notes

Growth Hormone (GH) Production and Regulation

  • GH and prolactin (PRL) are produced by specific cells in the anterior pituitary, regulated by the hypothalamus.
  • GH release is stimulated by growth hormone-releasing hormone (GHRH) and Ghrelin, but inhibited by somatostatin (SST), GH itself, and insulin-like growth factor 1 (IGF-1).
  • GH production is pulsatile, highest during sleep, stimulated by GHRH and Ghrelin, inhibited by SST, GH, and IGF-1.
  • GH production is high in infancy, peaks during puberty, and decreases in adulthood.
  • GH binds to cell-surface GH receptors (GHR) and activates them, stimulating the production of IGF-1, mainly by the liver.
  • Elevated GH and IGF-1 levels induce negative feedback loops, inhibiting further GH secretion.

GH Actions and Effects

  • GH promotes longitudinal bone growth, and increases glycolysis and body fat storage, supporting muscle mass, immune function, cardiovascular health, and nervous system well-being.
  • GH Hypersecretion: Leads to gigantism in childhood and acromegaly in adulthood, characterized by abnormal longitudinal bone growth.
  • GH Deficiency/Signal Disruption: Causes short stature, or rare syndromes.

GH Receptors

  • Similar to cytokine receptors, lacking intrinsic kinase activity.
  • Rely on the recruitment of non-receptor tyrosine kinase JAK2 for activation.

GH Receptor Activation Pathway

  • GH binding activates JAK2 within the receptor.
  • JAK2 phosphorylates downstream targets, including STAT5.
  • STAT5 dimerizes and enters the nucleus, modulating gene transcription.
  • Genes involved in growth, metabolism, and sex dimorphism are affected.
  • Replacement Therapy (Somatotropin): Uses GH analogues to treat GH deficiency.
  • GH Receptor Bypass: In cases of receptor dysfunction, IGF-1 replacement (mecasermin) is used, aiming to mimic the effects of GH.
  • GH Release Stimulation (Tesamorelin): Synthetic GHRH analogue mimicking hypothalamic function, reduces visceral fat accumulation.

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Description

This quiz covers the production and regulation of growth hormone (GH), including its stimulation and inhibition mechanisms, actions, and related pathologies. Explore how GH functions in promoting growth and maintaining health across different life stages.

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