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Endocrine physiology > Growth and development > Flashcards

Growth and development Flashcards

1
Q

What type of hormone is GH and how is it released?

A
  • GH is a peptide hormone released by the anterior pituitary gland
  • It is also known as somatropin
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2
Q

What is GH controlled by?

A

GH is controlled by the release of GHRH and GHIH (Somatostatin)

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3
Q

Which hormones are permissive to the effect of GH?

A

Thyroid hormones and insulin

  • Poorly controlled diabetes results in stunted growth
  • Hypothyroidism can also result in stunted growth
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4
Q

Describe growth in the foetal period and first 8-10 months of birth

A
  • Largely influenced by nutritional factors

- GH takes over after the 8-10 month growth period

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5
Q

Describe GH in adult life

A
  • Continuous to be secreted throughout adult life as it is essential to tissue repair
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6
Q

Describe the indirect action of GH

A

Mainly achieved through the actions of IGF-1 aka somatomedin C

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7
Q

Describe the secretion of IGF-1 and the type of hormone

A

IGF-1 is a peptide hormone secreted by the Liver in response to GH release

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8
Q

How are GH and IGF-1 transported in the blood

A

Despite being peptide hormones, they are transported in the blood like steriod and thyroid hormones

  • Bound to plasma proteins, this helps create a resivoir of GH and also extends half life
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9
Q

Describe GH/IGF-1 on growth

A
  1. GH stimulates chondrocytes precursor (prechondryctyes) cells in the epiphyseal plate to differentiate into chondrocytes
  2. During this differentation they begin to secrete IGF-1
  3. IGF-1 then acts in an autocrine and paracrine fashion to stimulate cartilage and cell division
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10
Q

What are the direct effects of GH which are diabetogenic

A
  1. Increases gluconeogensis in the liver
  2. Reduces the ability of insulin to stimulate glucose uptake by muscle and adipose tissue
  3. Makes adipocytes less sensitive to lipolytic stimuli

All of these actions from GH release energy stores

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11
Q

What are the direct effects of GH that aren’t diabetogenic

A

Increases amino acid uptake and protein synthesis in almost all cells

Much like insulin it has an anabolic protein action

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12
Q

Summarise the direct effects of GH

A
  1. Increases gluconeogensis
  2. Inhibits the actions of insulin on receptors
  3. Promotes lipolysis providing source of energy for the new cells
  4. Promotes amino acid uptake in cells, supporting protein synthesis
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13
Q

When in life is GH secretion at its highest and when throughout sleep is it highest?

A
  • Highest rates of secretion occur during the teenage years
  • ## Majority of GH secretion occurs during delta sleep (Tue first 2 hours of sleep)
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14
Q

What stimuli increase GHRH production

A
  • Exercise
  • Cold
  • Increased amino acids in the system
  • Stressful stimuli
  • Delta sleep
  • Oestrogen and testosterone
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15
Q

What stimuli increase GHIH production

A
  • Glucose (Why secrete more when already adundance)
  • FFA (Why secrete more when already abundance)
  • REM sleep
  • Cortisol (Protein catabolism)
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16
Q

Babies born deficent of GH and IGF-1 are effected how?

A

They arent effective, GH only effects

17
Q

What are thyroid hormones function in growth?

A

Thyroid hormones are essential for growth in utero and early childhood

Thyroid hormone has a permissive action on GH

Thyroid hormone is essential to bone ossification and face contour

18
Q

What is cretinism?

A

Cretinism is a condition where children are hypothyroid from birth, this means the permissve actions of thyroid hormones on GH is lost

Infantile facial features are retained

19
Q

What is the importance of nutrion?

A

Essential in growth and development

- Important in utero and during development

20
Q

What is the effect of infection on growth

A
  • Infection can stunt growth due to increase protein cataobolism
21
Q

Describe the 2 periods of rapid growth

A
  1. Infancy, period where 2.5cm of height each day, then nothing
  2. Puberty, sex hormones androgens and oestrogen produce spikes in GH secretion that increase IGF-1 and growth

Also responsible for fusel of epiphyseal plates

22
Q

Describe the consequences of hyper secretion of GH before the closing of the epiphyseal plates?

A
  • Results in massive elongation of bones are gigantism

- Excessive growth may be more than 7ft tall

23
Q

Describe the consequence of hyper secretion of GH after the closing of epiphyseal plates?

A
  • Results in acromegaly

- Enlarged hands and feet results in growth in other directions

Endocrine physiology (11 decks)

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