Growth Hormone and Its Effects

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Questions and Answers

Which cell types, besides the liver, release somatomedin in response to growth hormone (GH)?

Adipocytes

Chondrocytes

Osteoblasts (correct)

Myocytes

What primarily differentiates Laron dwarfism from pituitary dwarfism?

Insufficient GH levels

Excess GH production

Nutritional deficiencies

GH receptor insensitivity (correct)

What is the primary characteristic of gigantism?

GH receptor malfunction

Excess GH production in adulthood

Excess GH production during childhood (correct)

Insufficient GH production in childhood

How much of the genetic growth potential is influenced by growth hormone (GH)?

Approximately 30% Signup and view all the answers

What role does GH play during the fed state in terms of metabolic actions?

It promotes protein synthesis. Signup and view all the answers

Which of the following describes acromegaly?

GH overproduction in adulthood Signup and view all the answers

What metabolic action occurs during fasting due to GH?

Mobilization of fat stores Signup and view all the answers

What is the effect of GH and IGF-1 during periods of favorable nutritional status?

They promote anabolic growth. Signup and view all the answers

What is a primary physiological function of somatomedin?

Mediating GH effects on growth Signup and view all the answers

Which condition arises from an excess of growth hormone after puberty?

Acromegaly Signup and view all the answers

What primarily mediates the effects of growth hormone on stature?

Release of somatomedin Signup and view all the answers

In what way does growth hormone influence adipose tissue?

Promotes lipolysis to reduce fat stores Signup and view all the answers

Which tissue's response is enhanced by growth hormone through increased protein synthesis?

Muscle tissue Signup and view all the answers

How does growth hormone contribute to linear growth of long bones?

By enhancing chondrocyte proliferation at the growth plate Signup and view all the answers

What role does the liver play in the action of growth hormone?

It releases somatomedin in response to growth hormone Signup and view all the answers

Which statement about the direct effects of growth hormone is true?

It decreases glucose utilization in most tissues Signup and view all the answers

What is the result of growth hormone stimulating insulin-like growth factors (IGFs)?

Enhanced differentiation and activity of chondrocytes Signup and view all the answers

Which of the following statements best describes the effects of growth hormone on bone metabolism?

Stimulates osteoblast activity to promote bone formation Signup and view all the answers

Which of the following is NOT a function associated with growth hormone?

Increasing insulin sensitivity Signup and view all the answers

What process in cartilage and bone is directly stimulated by growth hormone through IGFs?

Proliferation of chondrocytes Signup and view all the answers

What hormone is primarily responsible for the synthesis and secretion of milk during lactation?

Prolactin Signup and view all the answers

What effect does compromising the pituitary stalk have on prolactin secretion?

Increases prolactin secretion Signup and view all the answers

What hormone from the hypothalamus stimulates the synthesis of growth hormone?

Growth hormone-releasing hormone (GHRH) Signup and view all the answers

Which factor is crucial for establishing lactation post-delivery?

Immediate initiation of nursing Signup and view all the answers

What type of feedback mechanism regulates prolactin secretion?

Neuro-endocrine feedback loop Signup and view all the answers

What condition is associated with the absence of thyroid hormone in childhood?

Cretinism Signup and view all the answers

What physiological action is primarily induced by oxytocin during lactation?

Ejection of milk Signup and view all the answers

Which factor serves as the primary negative feedback regulator of growth hormone secretion?

IGF-1 Signup and view all the answers

Which of the following is NOT a stimulatory factor for growth hormone secretion?

Elevated blood pressure Signup and view all the answers

What is the impact of the hypothalamus on prolactin secretion under normal circumstances?

It exerts an inhibitory influence on prolactin secretion Signup and view all the answers

How do growth hormone levels in children compare to those in adults?

They are higher in children. Signup and view all the answers

When does the final arrangement of epithelial cells in the mammary gland occur?

After the loss of pregnancy hormones with the delivery of the placenta Signup and view all the answers

What happens to growth hormone secretion as individuals age?

It declines. Signup and view all the answers

What is critical for the maintenance of lactation?

Consistent suckling Signup and view all the answers

What physiological response is activated by ghrelin regarding growth hormone?

Stimulates secretion of growth hormone Signup and view all the answers

Which hormone with lactogenic properties is secreted by lactotropes?

Prolactin Signup and view all the answers

Which phase is essential for continued milk production in a mature mammary gland?

Stimulation by prolactin Signup and view all the answers

During which time period is the largest release of growth hormone typically observed?

Early hours of sleep Signup and view all the answers

What role does thyroid hormone play in growth hormone synthesis?

It is required for the formation of normal amounts of growth hormone. Signup and view all the answers

Why do adults continue to produce growth hormone throughout life?

Due to its important role in metabolism. Signup and view all the answers

Study Notes

Physiology Lecture 22: Hypothalamus and Pituitary Hormones

Growth Hormone (GH) Synthesis Stimulation: Growth hormone (GH) synthesis is stimulated by growth hormone-releasing hormone (GHRH) from the hypothalamus.
Thyroid Hormone Requirement: Thyroid hormone is needed for normal amounts of GH formation.
Cretinism: Absent thyroid hormone results in cretinism, a condition characterized by short stature.
GH Half-life: GH has a specific half-life.

GH Secretion Regulation

IGF-1 and Ghrelin:
- IGF-1 is a primary negative feedback regulator of GH secretion due to its longer half-life, aided by binding proteins.
- Ghrelin, released from the gut, stimulates GH secretion, though its precise function isn't fully understood.
Stimulatory Factors: Stress, hypoglycemia, amino acids (like arginine), and traumatic or psychogenic stress stimulate GH secretion.

GH Secretion Patterns

Diurnal Rhythm: GH secretion follows a daily rhythm, with the largest release occurring during the early hours of sleep.
Childhood vs. Adulthood: GH levels are higher in children than in adults, peaking during puberty.
Aging and GH: GH secretion declines with aging.

Growth Hormone Actions

Promoting Bone Growth: GH promotes the growth of long bones, aiding in stature development.
Metabolic Actions: GH stimulates insulin-like growth factors (IGFs), enhances lean body mass by promoting protein synthesis and fat utilization.
Bone Metabolism: GH stimulates osteoblast activity, promoting bone formation and remodeling; encouraging long bone growth by stimulating chondrocyte proliferation at the epiphyseal plate

GH and Bone Growth

Liver's Role: The liver is a target organ for GH, releasing somatomedin in response to GH.
Somatomedin Effects: Somatomedin, released by the liver and other cells, mediates the effects of GH on stature.

Pituitary Dwarfism and Gigantism

Pituitary Dwarfism: Caused by a lack of GH during childhood.
Laron Dwarfism: Caused by a lack of response to GH due to GH receptor issues.
Gigantism: Caused by overproduction of GH during childhood, leading to a very tall stature approximately 8 feet.

Factors Affecting GH and Growth

Genetic Potential: GH influences about 20-30% of genetic growth potential, acting as a growth facilitator.
Metabolic States: In the fed state, GH promotes anabolic growth; in the fasting state, GH is catabolic, mobilizing energy.

Prolactin

Secretion and regulation: Secreted by lactotrophs in the anterior pituitary; controlled by a neuroendocrine feedback loop; Hypothalamus normally exerts an inhibitory influence on prolactin secretion.
Mammary Development and Lactation: Prolactin plays a role in the growth, stimulation, and milk synthesis and secretion of the mammary gland during pregnancy and lactation;
Compromised Pituitary Stalk: Prolactin secretion rises if the pituitary stalk is damaged.
Oxytocin Role: Oxytocin is responsible for the ejection of milk from the mammary gland.
Mammary Gland Effects of Prolactin: Elevated levels of prolactin (e.g., prolactinomas) can cause reproductive problems.

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Description

This quiz explores the various effects of growth hormone (GH) on the body, including its role in growth, metabolism, and related conditions. Test your knowledge on somatomedin, dwarfism, gigantism, and acromegaly, along with influencing factors of GH on growth potential and adipose tissue. Understand the complexity of GH's actions during different physiological states.