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Additional Endocrine Flashcards > Endocrine Control Of Growth And Disorders Of Growth > Flashcards

Endocrine Control Of Growth And Disorders Of Growth Flashcards

1
Q

What are 3 factors affecting growth>

A

Genetics
Nutrition
Hormones

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2
Q

What hormones affect growth?

A

GH (GHRH and GHIH_)
IGF-1
Thyroid hormone
Insulin
Sex steroids
Cortisol (antagonist)

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3
Q

When are the periods of rapid growth?

A

Infancy
Puberty

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4
Q

What happens in infancy growth?

A

Growth in foetal period and the first 8-10 months of life.
Largely controlled by nutritional intake, thyroid hormones and insulin.
GH become significant from around 10 months

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5
Q

What happen in rapid growth at puberty?

A

Due to androgens and oestrogen.
Produces spikes in GH secretion that increase IGF-I -> increase growth.
The same sex steroids also terminate growth by causeing the epiphysis of long bones to fuse.
Before the epiphyseal plates fuse, GH/ IGF-I promote bone elongation and increase height, weight and body mass
Sex hormones in the later stages of puberty act to close epiphyses and hence stop elongation

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6
Q

What hormones contribute to growth?

A

GH, IGF-I, thyroid hormones, sex steroids, glucocorticoids and insulin

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7
Q

What are sex hormones influence?

A

Minor until puberty when they dominate the growth spurt

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8
Q

What is GH influence?

A

Minor during foetal life. Babies born deficit of GH and IGF-1 are of normal size

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9
Q

What hormones dominate intra-uterine growth?

A

Thyroid hormones, insulin and IGF-II

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10
Q

What are thyroid hormones important for?

A

Development of the nervous system in uteri and early childhood

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11
Q

What is congenital hypothyroidism?

A

Condition where babies are born of normal size but cannot produce own TH

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12
Q

what happens if congenital hypothyroidism is left untreated?

A

Retarded growth and development. They retain infantile facial features

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13
Q

What is something that may result in severely retarded intra-uterine growth?

A

Maternal iodine deficiency

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14
Q

What effect does TH have on GH?

A

Permissive

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15
Q

How does loss of TH affect GH?

A

Severely impact on GH action

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16
Q

How do hypothyroid children appear?

A

Retain infantile properties

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17
Q

How do children deficient in GH appear?

A

Proportionally normal, just small

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18
Q

What kind of hormone is GH?

A

Peptide

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19
Q

What is GH also known as?

A

Somatotropin

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20
Q

What cells is GH release from?

A

Somatotroph cells

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21
Q

What control the release of GH?

A

GHIH and GHRH

22
Q

What determines the balance of GHRH and GHIH?

A

Composition of factors that impinge on the hypothalamus

23
Q

What age does GH become the dominant influence?

A

10 months of age

24
Q

What does GH need to stimulate growth?

A

Permissive effects of TH and insulin

25
Q

What can poorly controlled diabetes in children cause?

A

Stunted growth

26
Q

Does GH secretion continue throughout life?

A

Yes, as it is essential to maintain and repair tissue

27
Q

What does GH promote in many target tissues?

A

Increase in both cell size and cell digision

28
Q

What does GH act on?

A

Tyrosine kinase receptor

29
Q

What happens after GH acts on tyrosine kinase receoptor?

A

Resulting phosphorylation of intracellular tergets brings about a myriad of effects that can be generalised into two broad actions

30
Q

What actions can the effect of GH be generalised into?

A

Growth of long bone
Regulation of metabolism

31
Q

What effect does GH have on skeletal growth?

A

Indirect effect
Achieved through the action of insulin like growth factor - 1, aka somatomedin C, as it mediates the action of GH

32
Q

What qualities does IGF-1 have?

A

Insulin like qualities, it stimulates glucose uptake in muscle and bone

33
Q

What is IGF secreted by?

A

Liver

34
Q

What triggers the release of IGF?

A

GH release
IGF controls the release of GH through negative feedback loop

35
Q

What type of hormone is GH and IGF?

A

Peptide hormone

36
Q

What influences the closure of epiphyseal growth plates?

A

Sex steroids

37
Q

What happens after epiphyseal growth plate close?

A

Longitudinal growth is no longer possible

38
Q

How does GH influence metabolism>

A

1 increase gluconeogenesis by the liver
2 reduce the ability of insulin to stimulate glucose uptake by muscle and adipose tissue
3 makes adipocytes more sensitive to lipolytic stimuli
4 increases amino acid uptake and protein synthesis in almost all cells= anabolic effect

39
Q

When is the highest rate of secretion of GH?

A

Teenage years

40
Q

When is the majority of growth hormone released?

A

In the first 2 hours of sleep

41
Q

During GH spikes what happens to IGF levels and why?

A

Remain relatively constant.
This is because it binds more tightly to carrier proteins than GH, so is less vulnerable to degradation

42
Q

what are stimuli that increase GHRH?

A

Actual or potential decrease in energy supply to cells. GH needed for maintenance of tissues and their energy supply. I fasting and hypoglycaemia decrease in substrate supply. In exercise and in the cold increase demand for energy. All stimulate increase in GH.
Increased amounts of amino acids in the plasma. GH promotes AA transport and protein synthesis by muscle and liver.
Physical stress and illness although growth may actually be stunted due to catabolic action of cortisol
Delta sleep increase in GH may be related to growth spurts in children and adolescents and tissue repair in adults.
Oestrogen and testosterone stimulate GH release from pituyatary directly and decrease IGF mediated negative feedback. Responsible for growth spurt

43
Q

What are stimuli that increase GHIH?

A

Glucose
FFA
Ageing
Cortisol

44
Q

What causes hypersecretion?

A

Endocrine tumour

45
Q

What are two pathologies of GH hypersecretion?

A

Gigantism and acromegaly

46
Q

What is gigantism?

A

XS GH due to pituatary tumour before epiphyseal plate of long bones close -> excessive growth

47
Q

What is acromegaly?

A

XS gh due to pituatary tumour after epiphyseal plates have sealed. Long bones cannot increase so there is not longitudinal growth and no increase in height. Can still grow in other directions and characteristic features are enlarged hands and feet

48
Q

What is a classic sign of acromegaly?

A

Feet getting bigger

49
Q

How do you treat hypersecretion?

A

Surgery to remove tumour or somatostatin analogues

50
Q

What is a small stature due to?

A

A deficiency of GHRH.
Deficiency of GH
Genetic mutation or under expression of GH receptor. Depress downstream release of IGF-1 and peripheral tissues cannot respond to growth signal. Loss of IGF inhibition leds to increase gh
Precocious puberty. XS GnRH release stimulates puberty via promoting sex hormone release. These children have stunted because long bones fuse early under influence of sex hormones.
Hypothyroidism dwarfism- children retain infantile features wuth stunted growth due to loss of permissive effect of TH on GH. Impact may be moderated by early detection and supplementation with TH

Additional Endocrine Flashcards (2 decks)

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