Growth Hormone and IGF Overview

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Questions and Answers

What is a primary effect of growth hormone (GH) on glucose regulation?

Decreases glucose entry into cells (correct)

Stimulates pancreatic insulin production

Promotes insulin sensitivity

Increases glucose entry into cells

What role do Insulin-like Growth Factor Binding Proteins (IGFBPs) play in the body?

Promote protein breakdown

Enhance growth hormone secretion

Decrease IGF half-life in circulation

Regulate IGF availability to receptors (correct)

Which Insulin-like Growth Factor (IGF) is primarily stimulated by growth hormone and nutritional status?

IGF-2

IGFBP-3

IGF-1 (correct)

IGFBP-1

What is the most common manifestation of growth hormone deficiency in children pre-puberty?

Height below the 3rd percentile Signup and view all the answers

What effect does IGFBP-1 have on growth?

Inhibits growth Signup and view all the answers

Which of the following is NOT an effect of growth hormone?

Decreases protein synthesis Signup and view all the answers

What condition results from growth hormone deficiency typically seen in children?

Height below the 3rd percentile Signup and view all the answers

What is a common manifestation of growth hormone deficiency in prepuberty?

Delayed or absent pubertal development Signup and view all the answers

What is the primary function of IGFBP-3?

Carries IGF in circulation Signup and view all the answers

Which statement best describes the relationship between growth hormone and blood glucose levels?

GH increases blood glucose through insulin resistance Signup and view all the answers

Which method is commonly used to assess skeletal maturation in cases of growth hormone deficiency?

X-ray of the left hand Signup and view all the answers

What condition is characterized by growth hormone insensitivity?

Laron syndrome Signup and view all the answers

Which IGF is characterized by 70 amino acids and 50% homology with insulin?

IGF-1 Signup and view all the answers

Which of the following tests is considered a hormone stimulation test for assessing growth hormone deficiency?

Arginine stimulation test Signup and view all the answers

What is a major risk associated with the lack of growth hormone post-puberty?

Altered metabolism Signup and view all the answers

Which of the following symptoms is associated with acromegaly?

Thickening of skin Signup and view all the answers

What is the typical age range for the development of acromegaly?

30 to 50 years Signup and view all the answers

Which of the following is NOT a common effect of GH deficiency?

Enhanced quality of life Signup and view all the answers

What causes the symptoms associated with gigantism?

Benign tumor of the pituitary gland Signup and view all the answers

What characterizes genetic IGF deficiency?

Defect in the signaling pathway of GH and IGF1 Signup and view all the answers

Study Notes

Growth Hormone Effects

Growth hormone (GH) has direct and indirect effects on the body
Direct effects include increasing amino acid uptake, protein synthesis, and decreasing protein breakdown
GH also impacts glucose uptake, leading to increased blood glucose levels (hyperglycemia).
This is because GH reduces glucose uptake and increases glucose production, leading to insulin resistance.

IGF and Insulin Receptors

IGF-1 and insulin receptors share a structural similarity
IGF-1 receptors have an important metabolic effect and a mitogenic effect.
Insulin receptors have a major metabolic effect.
Important for growth as they are both involved in cell growth, differentiation and functions.

IGF Family

IGF binding proteins (IGFBPs) bind to insulin-like growth factor (IGF) in the blood
These proteins act as carriers, increasing IGF lifetime in the circulation
IGFBPs regulate IGF-receptor access, having independent functionality to IGF itself
Different IGFBPs have different effects (e.g., IGFBP-3 promotes growth, IGFBP-1 inhibits it), impacting overall growth and development.

IGFBP- Modifying IGF activity

IGFBP-3 is the most common form of IGFBP
IGFBP-3 is a primary carrier of IGF in the circulation and promotes somatic growth. High IGFBP-3 is associated with growth stimulation.
IGFBP-1 is typically present in smaller amounts and is associated with growth inhibition.

Binding Proteins and Receptors

Binding proteins of IGF regulate IGF availability to receptors in the body
Different levels of binding proteins lead to different states of IGF receptor activity. E.g. increased placental IGF, decreased decidual IGFBP-1 levels result in unlimited invasion.

Insulin-like Growth Factors - Somatomedins

IGF-1 (somatomedin C) is 70 amino acids and has a 50% homology with insulin
IGF-2 is 67 amino acids with 70% insulin homology
Stimuli for secretion include GH and nutritional status.

Bone Cell-Specific Effects of IGFs

IGFs promote proliferation, maturation, and differentiation of bone cells involved in bone development.
IGFs regulate stem cell pools contributing to bone lineage commitment.
IGFs influence osteoclast activity, fusion, and multinucleation.
They interact with the osteocyte network maintaining integrity.

Other Effects of Growth Hormone

Adipose tissue – increased lipogenesis.
Extra skeletal tissue – cells growth proliferation and protein synthesis
Effects on blood glucose (diabetogenic effect): Overall increase in plasma glucose, insulin resistance, reductions in glucose uptake, and pituitary diabetes.

GH Hormone Deficiency: Pre-Puberty

Most frequent pituitary hormone deficiency in childhood
Can be isolated or accompanied by deficiency in other pituitary hormones.
Panhypopituitarism (rare) is a condition involving a reduced production of all pituitary hormones.
GH deficiency leads to slow growth and short stature.

Growth Hormone Deficiency: Pre-puberty (Clinical manifestations)

Growth failure, with height below the 3rd percentile
Typically characterized by slow growth velocity (less than 6 cm/year before age 4, less than 5 cm/year from age 4 to 8, and less than 4 cm/year before puberty).
Small stature, and relatively normal body proportions.
Delayed skeletal maturation, usually 2 years or more behind the child's chronological age.
Delays in tooth development, pubertal development, relative obesity.
Possible hypoglycemia or manifestations of other endocrine issues.

GH Pre-Puberty Deficiency Assessment and Diagnosis

Comprehensive data collection: height and weight recorded on a growth chart
Medical imaging, including X-rays (bone age), and MRI (for pituitary gland & hypothalamus evaluation) along with structural anomalies
Hormone and binding protein measurements, along with GH stimulation tests (e.g., arginine).

Growth Deficiencies Unrelated to GH Deficiency

Laron syndrome (GH insensitivity or primary IGF-1 deficiency): rare genetic disease, inherited in autosomal recessive pattern. Genetic mutations of growth hormone receptor gene impacting the GH/IGF-1 signaling pathway
Nutritional Neglect
Genetic IGF Deficiency

Undersecretion Post-Puberty

Lack of GH post-puberty: altered metabolism, increased adiposity, increased tiredness.
Increased cardiovascular disease risk.
Anxiety and depression
Reduced "quality of life"

Over-Secretion of GH

Age-dependent gigantism (pre-puberty): Characterized by excessive growth during childhood.
Post-puberty: Acromegaly: A condition with an overproduction of GH in adulthood. Slow bone and soft tissue growth, leading to characteristic enlarged bones, and soft tissue structures in the face, hands, and feet. Thickened skin and a broader face and larger hands and feet.

Acromegaly Symptoms

Thickened skin, coarse facial features, enlarged hands, feet, and lips, nose and tongue
Jaw protrusion, ribs thickening leading to barrel chest, organ enlargement (CV disease risk), upper airway obstructions ("sleep apnea")
Carbohydrate intolerance, pituitary diabetes and general tiredness.

Fetal Growth

Factors that control fetal growth are complex and not fully understood

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Description

Explore the effects of growth hormone on the body, including its role in protein synthesis and glucose regulation. Learn about the similarities between IGF-1 and insulin receptors, as well as the importance of IGF binding proteins in metabolic processes. This quiz will deepen your understanding of hormonal interactions and their physiological impacts.