Hypothalamus and Pituitary Hormones Overview
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Questions and Answers

What stimulates the synthesis of growth hormone (GH)?

  • Cortisol
  • Insulin
  • Thyroid hormone
  • Growth hormone-releasing hormone (GHRH) (correct)

The absence of thyroid hormone can lead to increased growth in children.

False (B)

What is the role of IGF-1 in GH secretion?

Primary negative feedback regulator

Incretin, specifically ______, is a known stimulator of GH secretion.

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

Which factor is NOT a stimulatory factor for GH secretion?

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

How do GH levels differ between children and adults?

<p>GH levels are higher in children than in adults.</p> Signup and view all the answers

Match the hormone to its function:

<p>GHRH = Stimulates GH synthesis Ghrelin = Stimulates GH secretion IGF-1 = Negative feedback regulator of GH Thyroid hormone = Required for normal GH formation</p> Signup and view all the answers

Adults stop producing GH as they age.

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

What is one of the primary actions of growth hormone (GH) regarding bones?

<p>Stimulates osteoblast activity (A)</p> Signup and view all the answers

Growth hormone directly promotes fat storage in adipose tissue.

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

Name the factors released by the liver in response to growth hormone that aid in growth.

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

Growth hormone enhances ___ synthesis, leading to increased muscle mass.

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

Match the following effects with their corresponding target tissues:

<p>Adipose Tissue = Promotes lipolysis Bone = Stimulates osteoblast activity Muscle = Enhances protein synthesis Liver = Releases somatomedin in response to GH</p> Signup and view all the answers

Which of the following statements about the linear growth effects of growth hormone is correct?

<p>It promotes chondrocyte proliferation at the growth plate. (D)</p> Signup and view all the answers

Growth hormone decreases glucose utilization in most tissues.

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

What role does the liver play in growth hormone-mediated growth?

<p>Releases somatomedin</p> Signup and view all the answers

Which condition is characterized by a lack of growth hormone during childhood?

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

Laron dwarfism results from a lack of growth hormone receptors.

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

What is the primary effect of growth hormone during fasting?

<p>Mobilizes fat while sparing glucose and protein</p> Signup and view all the answers

Gigantism is characterized by overproduction of GH during __________.

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

Which of the following statements best describes acromegaly?

<p>It occurs due to overproduction of GH in adulthood. (C)</p> Signup and view all the answers

Match the conditions with their causes:

<p>Pituitary dwarfism = GH deficiency during childhood Laron dwarfism = GH receptor issue Gigantism = Overproduction of GH during childhood Acromegaly = Overproduction of GH in adulthood</p> Signup and view all the answers

What percentage of genetic growth potential is influenced by growth hormone?

<p>30% (D)</p> Signup and view all the answers

What role do somatomedin play in response to GH?

<p>They are released from various cells, including those in bone.</p> Signup and view all the answers

In the fed state, GH and IGF-1 promote anabolic growth.

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

What hormone is secreted by lactotropes in the anterior pituitary?

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

Lactotropes are part of an endocrine axis.

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

What happens to prolactin secretion if the pituitary stalk is compromised?

<p>Prolactin secretion increases.</p> Signup and view all the answers

Prolactin secretion is regulated by a __________ feedback loop.

<p>neuro-endocrine</p> Signup and view all the answers

What is the role of oxytocin in lactation?

<p>Ejecting milk from the mammary gland (A)</p> Signup and view all the answers

Nursing should be initiated immediately to maintain exposure to low levels of prolactin.

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

What is required for the production of milk in the mature mammary gland?

<p>Continued stimulation by prolactin.</p> Signup and view all the answers

Match the following terms with their relevant functions in lactation:

<p>Prolactin = Synthesis and secretion of milk Oxytocin = Ejection of milk Nursing = Maintaining exposure to prolactin Pituitary stalk compromise = Increased prolactin secretion</p> Signup and view all the answers

Flashcards

What stimulates the synthesis of growth hormone (GH)?

Growth hormone-releasing hormone (GHRH) from the hypothalamus stimulates the synthesis of growth hormone.

What is required for the formation of normal amounts of growth hormone?

Thyroid hormone is essential for normal growth hormone production.

What condition results from absent thyroid hormone, and how does it affect growth?

Cretinism is a condition resulting from absent thyroid hormone. It causes short stature, among other symptoms.

What is the role of incretin (Ghrelin) in GH secretion?

Ghrelin, an incretin released from the gut, stimulates growth hormone secretion, even though its exact function is not fully understood.

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What role does IGF-1 play in the regulation of GH secretion?

Insulin-like growth factor 1 (IGF-1) acts as the primary negative feedback regulator of GH secretion due to its longer half-life and its association with binding proteins.

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What are some stimulatory factors for GH secretion?

Stress (physical or psychological), hypoglycemia (low blood sugar), amino acids like arginine, and traumatic events all stimulate growth hormone release.

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How do GH levels differ between children and adults?

Children have higher GH levels than adults. Levels peak during puberty.

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What happens to GH secretion with aging?

Growth hormone secretion decreases with age. Adults continue to produce it because of its role in metabolism.

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GH and Adult Stature

Adult stature is greatly impacted by growth hormone (GH) during childhood.

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Pituitary Dwarfism

Pituitary dwarfism is a condition caused by a lack of growth hormone (GH) during childhood.

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Laron Dwarfism

Laron dwarfism occurs due to a lack of response to GH because of a deficiency in GH receptors.

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Gigantism

Gigantism is caused by excessive GH production during childhood, resulting in significant height.

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Acromegaly

Acromegaly results from excessive GH production in adulthood, causing changes in bone size and thickening of features.

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GH and Genetic Growth Potential

GH facilitates the expression of genetic growth potential.

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GH's Impact on Growth

The influence of GH on genetic growth potential is estimated to be approximately 30%.

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GH's Anabolic Role in the Fed State

GH promotes protein synthesis, cell growth, and tissue repair, playing an anabolic role in the fed state.

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How does Growth Hormone (GH) affect linear growth?

Growth hormone (GH) directly stimulates the production of Insulin-like Growth Factors (IGFs) in the liver, which then act on the growth plate to promote cartilage growth.

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What is the effect of GH on adipose tissue?

GH promotes lipolysis, increasing the availability of free fatty acids for energy.

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What is the effect of GH on muscle tissue?

GH stimulates protein synthesis, leading to increased muscle mass and strength.

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How does IGF-1 contribute to linear growth?

IGF-1 stimulates chondrocyte proliferation and differentiation at the growth plate, ultimately leading to bone elongation.

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What is the impact of GH on overall body composition?

GH enhances protein synthesis, leading to increased lean body mass.

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How does GH contribute to bone metabolism?

GH stimulates osteoblast activity, leading to increased bone formation and remodeling.

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What effect does GH have on glucose utilization?

GH reduces glucose utilization, enhancing energy efficiency.

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How does GH contribute to energy generation?

GH promotes the release of free fatty acids by stimulating lipolysis in adipose tissue.

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What is prolactin?

Prolactin (PRL) is a hormone produced by lactotropes in the anterior pituitary. It plays a crucial role in lactation, pregnancy, and post-partum development.

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Are lactotropes part of an endocrine axis?

Lactotrope cells, unlike most other endocrine cells, are not part of a typical endocrine axis. Their secretion is primarily controlled by a neuro-endocrine feedback loop.

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How does the hypothalamus influence prolactin secretion?

The hypothalamus normally inhibits prolactin secretion. The pituitary stalk connects the hypothalamus to the pituitary gland, passing signals affecting prolactin release.

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What happens to prolactin secretion if the pituitary stalk is compromised?

If the pituitary stalk is compromised, prolactin secretion increases. This is because the inhibitory signals from the hypothalamus are disrupted.

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What controls prolactin secretion?

Prolactin secretion is regulated by a neuro-endocrine feedback loop, involving signals from the hypothalamus and feedback from the mammary glands.

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What is the role of oxytocin in lactation?

Oxytocin is released during breastfeeding, triggering milk ejection from the mammary glands. It's like a 'let-down' mechanism.

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What is the role of prolactin in lactation?

Prolactin is the primary hormone responsible for milk production and secretion. It stimulates the growth and development of the mammary glands.

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When does the final stage of mammary gland development occur?

The final stage of epithelial cell arrangement in the mammary gland, involving the basement membrane and tight junctions, is triggered after delivery when pregnancy hormones decline.

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Study Notes

Hypothalamus and Pituitary Hormones

  • Hypothalamus releases GnRH, TRH, CRH, GHRH, SRIF, and Dopamine, which stimulate the pituitary.
  • Pituitary releases LH, FSH, TSH, ACTH, GH, and PRL.
  • These hormones regulate various end organs like testis, ovaries, thyroid, adrenal, and breast tissues influencing gametogenesis, hormone production, and metabolism.

Growth Hormone (GH)

  • Stimulation: Growth hormone-releasing hormone (GHRH) from the hypothalamus stimulates GH synthesis.
  • Requirement for formation: Thyroid hormone is essential for normal GH amounts.
  • Absence of thyroid hormone: Causes cretinism marked by short stature.
  • GH half-life: The duration of GH in the bloodstream.

IGF-1 and Ghrelin

  • Ghrelin: A gut hormone, is a stimulator of GH secretion, though its precise role isn't fully understood.
  • IGF-1: A primary negative feedback regulator of GH, with a longer half-life.

GH Secretion Factors

  • Stimulatory factors: Stress, hypoglycemia, amino acids (e.g., arginine), and traumatic/psychogenic stress.

GH Secretion Activity

  • Multiple episodes: GH is secreted in multiple bursts, most notably during the early hours of sleep.
  • Diurnal rhythm: GH secretion follows an approximate daily pattern.
  • Persistent secretion: Secretion continues throughout life, even after growth ceases.
  • Differences in children and adults: GH levels are higher in children compared to adults, peaking during puberty.
  • Aging effect: GH secretion declines with age.

GH Secretion and Aging

  • Adults producing GH: Yes, because of the role of GH in metabolism.
  • Effect of senescence: GH levels fall during senescence.

Growth Hormone Actions

  • Growth: Promotes long bone growth (stature).
  • Metabolic effects:
    • Stimulates insulin-like growth factors (IGFs).
    • Enhances lean body mass by promoting protein synthesis and fat utilization.

Target Tissue Response to GH

  • Bone metabolism: Stimulates osteoblast activity, promoting bone formation and remodeling; encourages linear growth by stimulating chondrocyte proliferation at the epiphyseal plate.
  • Adipose tissue: Promotes lipolysis (fat breakdown), reducing fat stores, and increasing free fatty acid availability for energy.
  • Muscle: Enhances protein synthesis, increasing muscle mass and strength.

Extending Bone Growth

  • GH stimulates IGF production, which directly stimulates chondrocyte (cartilage cells) proliferation and activity within the growth plate of long bones.

Role of Liver in GH-Mediated Growth

  • The liver is a target organ for GH and releases somatomedin in response to GH.

Other Cell Types in GH-Mediated Growth

  • Besides the liver, other cell types, such as bone cells, also release somatomedins in response to GH.

Pituitary Dwarfism

  • Results from a deficiency in GH production during childhood.

Laron Dwarfism

  • A lack of response to GH due to a receptor issue; different from pituitary dwarfism because of the lack of response to GH.

Gigantism

  • Results from the overproduction of GH during childhood leading to a very tall stature

Acromegaly

  • Overproduction of GH in adulthood, leading to enlarged bones and soft tissues. It's different from gigantism, which arises during childhood.

Metabolic Actions of GH- Fed vs Fasting

  • Fed state: GH is anabolic, promoting protein synthesis, cell growth, and tissue repair.
  • Fasting state: GH is catabolic, mobilizing energy through lipolysis and decreasing glucose uptake.

Metabolic Effects of GH (fasting/fed)

  • During fed states, GH and IGF-1 promote anabolic growth.
  • During fasting states, GH mobilizes fats and conserves protein.

Prolactin

  • Secretion: Produced by lactotropes in the anterior pituitary.
  • Role in lactation: Stimulates milk synthesis and secretion.
  • Regulation: A neuroendocrine feedback loop; hypothalamus inhibits prolactin secretion, but the pituitary stalk's compromise leads to prolactin increase.
  • Oxytocin's role: Ejection of milk from the mammary gland.
  • Estrogen impact: Estrogen enhances prolactin secretion.
  • Mammary gland function and pregnancy: Plays a role in the arrangement of the epithelial cells from the basement membrane and cell types.
  • Nursing initiation: Stimulating nursing after the loss of pregnancy hormones promotes lactation.

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Description

This quiz explores the roles of hypothalamus and pituitary hormones in regulating various body functions. It covers hormones such as GnRH, GHRH, and GH, along with their impacts on growth and metabolism. Test your understanding of these key endocrine processes!

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