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Endocrine > Growth and Development > Flashcards

Growth and Development Flashcards

1
Q

Name the factors that regulate growth

A
  • Growth hormone release from the anterior pituitary (which is regulated by GHRH and inhibited by GHIH)
  • Thyroid hormones
  • Insulin
  • Sex steroids
  • Availability of nutrients
  • Stress
  • Genetic
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2
Q

Where is growth hormone (aka somatotropin) released from?

A

It is released from the anterior pituitary

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3
Q

How is growth hormone release controlled?

A

By the release of two hypothalamic neurohormones: GHIH and GHRH

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4
Q

Name the actions of growth hormone

A
  • Growth and development

- Regulation of metabolism

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5
Q

Why are thyroid hormones and insulin important for growth?

A

They have a permissive effect on GH which is required for growth?

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6
Q

Which intermediate mediates the action of GH?

A

Insulin-like growth factor 1 (IGF-1)

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7
Q

Describe the features of IGF-1

A
  • It negatively inhibits GH release by inhibiting GHRH and GHIH
  • It has a structure very similar to pro-insulin
  • It binds to receptors very similar to the insulin receptor
  • It has hypoglycaemic properties although this us limited to glucose uptake in muscles
  • It is secreted by the liver and many other cell types in response to GH release
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8
Q

Describe the effects of GH and IGF-1

A
  • GH stimulates chondrocyte precursor cells in the epiphyseal plates to differentiate into chondrocytes
  • During the differentiation, the cells begin to secrete IGF-1 and become responsive to IGF-1
  • IGF-1 then acts as an autocrine or paracrine agent to stimulate the differentiating chondrocytes to undergo cell division and produce cartilage, the foundation for bone growth
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9
Q

What happens to the epiphyseal plates during adolescence?

A

They close under the influence of sex steroid hormones - no further longitudinal growth is possible

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10
Q

Describe the effects that GH has on metabolism

A
  • Increases gluconeogenesis by the liver
  • Reduces the ability of insulin to stimulate glucose uptake by muscle and adipose tissue
  • Increases amino acid uptake and protein synthesis in almost all cells
  • GH is diabetogenic in excess
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11
Q

When are GH levels in the body highest?

A
  • Highest in teenagers

- Highest in the first two hours of sleep (lowest during waking hours)

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12
Q

Name the stimuli that increase GHRH secretion

A
  • Actual or potential decrease in energy supply to cells
  • Increased amounts of amino acids in the plasma
  • Stressful stimuli
  • Increase in delta sleep
  • Oestrogen and testosterone
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13
Q

Name the stimuli that increase GHIH

A
  • Glucose
  • FFA
  • REM sleep
  • Cortisol
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14
Q

Name the hormones which have an effect on growth

A
  • GH
  • IGF-1
  • Thyroid hormones
  • Sex steroids
  • Glucocorticoids
  • Insulin
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15
Q

Describe how the thyroid hormones have an effect on growth

A
  • They are essential for normal growth particularly for the development of the nervous system in utero and early childhood
  • It is permissive to GH and IGF-1
  • They have widespread effects on ossification of cartilage and teeth maturation as well as the contours of the face and the proportions of the body
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16
Q

What is cretinism?

A
  • A condition where children are hypothyroid from birth
  • They have retarded growth because of the loss of TH’s permissive action on GH
  • They retain infantile facial features
  • GH levels are normal
17
Q

Name the two periods of rapid growth that humans go through

A
  • Infancy

- Puberty (due to androgens and oestrogens)

18
Q

Name the conditions caused by hypersecretion of GH and the difference between them

A
  • Gigantism: excess GH before the epiphyseal plates of the long bones close causing excessive growth
  • Acromegaly: occurs after the epiphyseal plates have sealed so there is no longitudinal growth (they can grow in other directions e.g. enlarged hands and feet
19
Q

List the different causes of Dwarfism

A
  • A deficiency of GHRH
  • Abnormal GH secreting cells
  • End organ is unresponsive to GH (Laron dwarfism)
  • Genetic mutations (pygmies have a genetic mutation that impairs IGF-1 production)
  • Precocious puberty (excess GnRH release)
  • Hypothyroid children (retain infantile proportions

Endocrine (5 decks)

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