Childhood Growth Flashcards

1
Q

List 6 conditions of body proportions.

A

1 - Short trunk dysplasia.

2 - Short limb dysplasia.

3 - Rhizomelia (short arms and thighs but not forearm and leg).

4 - Mesomelia (short forearms and legs but not arms and thighs).

5 - Acromelia (short hands and feet).

6 - Asymmetry.

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2
Q

List 2 changes in growth between infancy and childhood.

A

1 - Growth rate decreases from infancy to childhood.

2 - In infancy, growth is dependent on nutrition, whereas in childhood, growth is dependent on hormones (growth hormone and thyroid hormone).

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3
Q

What causes the growth spurt in teenagers?

A

The growth spurt is caused by sex hormones (oestrogen in females and testosterone in males).

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4
Q

What causes growth to end?

A
  • Growth ends with the fusion of epiphyses of long bones.
  • Fusion of epiphyses is due to the influence of oestrogen in both boys and girls.
  • In boys, the oestrogen is derived from aromatase converting testosterone to oestrogen.
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5
Q

Why is the average height for men greater than for women?

A

The average height for men is greater than for women because the growth spurt in the teenage years is greater for males than for females.

*Growth preceding the growth spurt is similar for males and females.

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6
Q

List 6 determinants of growth.

A

1 - Growth-promoting hormones.

2 - Genetics.

3 - Quality and duration of pregnancy.

4 - Nutrition.

5 - Health of organ systems.

6 - Psychosocial environment.

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7
Q

Where in the body does growth occur?

A

Growth occurs at growth plates (at the epiphyses of long bones).

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8
Q

List the processes that occur during growth.

A

1 - Chondrogenesis.

2 - Hypertrophy of chondrocytes.

3 - Osteogenesis.

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9
Q

Define chondrogenesis.

A

Chondrogenesis is the process by which cartilage is formed from condensed mesenchyme tissue, which differentiates into chondrocytes and begins secreting the molecules that form the extracellular matrix of the cartilage.

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10
Q

Define osteogenesis.

A

Osteogenesis is the replacement of a cartilaginous template with bone.

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11
Q

Why do chronic inflammatory diseases impair growth?

A

Chronic inflammatory disease impair growth because inflammatory mediators inhibit the growth of chondrocytes.

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12
Q

What is osteochondrodysplasia?

A
  • Osteochondrodysplasia is a primary growth plate abnormality resulting from a genetic defect of cartilage and bone growth.
  • It causes abnormal shapes and sizes of the skeleton, as well as disproportion of the long bones, spine and head.
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13
Q

List 5 causes of secondary growth disorders that cause reduced growth.

A

1 - Malnutrition.

2 - Chronic disease.

3 - Intrauterine growth restriction.

4 - Endocrine disorders (more in the next card).

5 - Psychosocial factors.

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14
Q

List 5 endocrine disorders that cause reduced growth.

A

1 - Growth hormone deficiency.

2 - IGF-1 deficiency.

3 - Hypothyroidism.

4 - Cushing’s syndrome.

5 - Pseudohypoparathyroidism (a genetic condition in which the body fails to respond to parathyroid hormone, which is produced in normal quantities).

6 - Rickets (vitamin D deficiency).

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15
Q

Describe the regulation of growth hormone secretion.

A

1 - The hypothalamus releases somatostatin and growth-hormone releasing hormone (GHRH).

  • Somatostatin, growth hormone and IGF-1 have a negative feedback effect on GHRH release at the hypothalamus.
  • The target of GHRH and somatostatin is the pituitary, where the effect of GHRH is positive and the effect of somatostatin is negative.

2 - The pituitary releases growth hormone.

  • Both growth hormone and somatostatin have a negative feedback effect on the release of growth hormone at the pituitary.
  • Its target is the liver (promoting IGF-1 secretion) and the bone (promoting growth).

3 - The liver secretes IGF-1.

  • IGF-1 has a negative feedback effect on its release at the liver.
  • Its target is the bone, where it causes growth.
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16
Q

In which nucleus do GHRH neurones have their cell bodies?

A

GNRH neurone have their cell bodies in the arcuate nucleus.

17
Q

Which hormone is measured to assess growth?

A

IGF-1 is measured to assess growth (not growth hormone because that has a pulsatile secretion whereas IGF-1 has a stable secretion).

18
Q

List 3 effects of growth hormone outside of the growth plates of the bone.

A

Growth hormone also causes:

1 - A decrease in glycolysis.

2 - An increase in lipolysis.

3 - An increase in muscle mass.

19
Q

List 3 factors that stimulate growth hormone secretion and 3 factors that suppress growth hormone secretion.

A

Factors that stimulate growth hormone secretion:

1 - Exercise.

2 - Stress.

3 - Hypoglycaemia.

Factors that suppress growth hormone secretion:

1 - Hypothyroidism.

2 - Ageing.

3 - Hyperglycaemia.

20
Q

List the types of IGF-1 deficiency.

A

Types of IGF-1 deficiency include:

1 - Primary IGF-1 deficiency (growth hormone insensitivity).

2 - Secondary IGF-1 deficiency (growth hormone deficiency).

3 - IGF-1 resistance.

*These are termed in relation to IGF-1 because IGF-1 is thought of as the main hormone controlling growth.

21
Q

Describe the signalling pathways triggered by growth hormone and IGF-1.

A
  • When growth hormone binds to the growth hormone receptor, 3 pathways are triggered:

1 - PI3K.

2 - Ras/raf/mek/erk.

3 - JAK/STAT.

  • This leads to the production of IGF-1.
  • When IGF-1 binds to the IGF-1 receptor, 2 pathways are triggered:

1 - PI3K.

2 - Ras/raf/mek/erk.

  • This leads to transcriptional regulation, causing growth.
22
Q

Why does IGF cause mild glucose-lowering effects?

A

IGF causes mild glucose-lowering effects because the IGF receptor and insulin receptor are structurally similar.

23
Q

To which proteins does IGF-1 bind to in the blood?

What are the functions of these proteins?

Where is this molecule produced?

A

1 - IGF-1 binds to IGF binding protein 3 (GFBPR3).

  • IGFBP3 is produced by Kupffer cells in the liver.
  • IGFBP3 is a carrier protein.

2 - IGF-1 binds to IGF acid labile subunit (IGFALS).

  • IGFALS is produced by hepatocytes (like IGF-1).
  • IGFALS doubles the half life of both IGFBP3 and IGF-1.
24
Q

What is idiopathic short stature (ISS)?

A
  • Idiopathic short stature is a familial growth deficiency that is classified into 3 types:

1 - Familial short stature.

2 - Delay of growth and puberty but with normal height prediction.

3 - A mixture of groups 1 and 2.

25
Q

What causes less severe short stature?

A

Less severe short stature can be caused by mild pleomorphism of only a small number of genes involved in determination of stature.

*The basic principle is that there are multiple genes involved in the determination of stature.

26
Q

List 4 conditions causing reduced stature.

A

1 - Precocious puberty.

2 - Congenital adrenal hyperplasia.

3 - McCune Albright syndrome.

4 - Hyperthyroidism (closes the growth plates prematurely).

27
Q

List 2 conditions causing increased stature during development but normal stature by adulthood.

A

1 - Beckwith-Wiedemann syndrome.

2 - Sotos syndrome.

28
Q

List 7 conditions causing increased adult stature.

A

1 - Androgen / oestrogen deficiency.

2 - Oestrogen resistance.

3 - Pituitary gigantism (growth hormone excess).

4 - Acromegaly (the same disorder of IGF-I excess as pituitary gigantism but occurs after the growth plate cartilage fuses in adulthood).

5 - Klinefelter’s syndrome.

6 - Marfan syndrome.

7 - Homocystinuria.