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endocrine > normal growth and clinical aspects > Flashcards

normal growth and clinical aspects Flashcards

1
Q

growth is regulated by a number of factors

A
  1. growth hormone release from anterior pituitary (regulated by balance of GHRH and GHIH)
  2. thyroid hormones
  3. insulin
  4. sex steroids (esp puberty)
  5. availability of nutrients
  6. stress
  7. genetics
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2
Q

growth hormone

A

peptide hormone released from anterior pituitary

aka somatotropin

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3
Q

what controls GH release

A

GHIH (somatostatin)

GHRH

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4
Q

balance of GHRH and GHIH

A

determined by the myriad of factors that impinge on the hypothalamus

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5
Q

actions of growth hormones

A

growth and development (indirect action)

regulation of metabolism (direct action)

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6
Q

what does GH require to stimulate growth

A

permissive action of thyroid hormones and insulin

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7
Q

growth-prompting effect of GH

A

mediated through stimulation of both cell size (hypertrophy) and cell division (hyperplasia) in its many target tissues

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8
Q

how is the effect of GH on growth indirect

A

it is achieved through the action of an intermediate known as insulin-like growth factor-1 (IGF-1) aka somatomedin C as it mediates the action fo GH

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9
Q

IGF-1 structure

A

very similar to pro-insulin

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10
Q

IGF-1 receptor

A

IGF-1 binds to receptors very similar to the insulin receptor and has hypoglycaemic qualities

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11
Q

when is IGF-1 secreted

A

by the liver (and many other cell types) in response to GH release

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12
Q

how does IGF-1 control GH release

A

through a negative feedback loop

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13
Q

how are GH and IGF-1 transported in the blood

A

bound to carrier proteins

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14
Q

IGF-1 negative feedback loop on GH release

A

IGF exhibits negative feedback in GH release both via inhibiting GHRH and stimulating GHIH

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15
Q

GH/IGF-1 effects on bone growth

A
  1. GH stimulates chondrocyte precursor cells in epiphyseal plates to differentiate into chondrocytes
  2. during differentiation, the cells begin to secrete IGF-1 and become responsive to IGF-1
  3. the IGF-1 then acts as an autocrine/paracrine agent to stimulate the differentiating chondrocytes to undergo cell division and produce cartilage (the foundation for bone growth)
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16
Q

GH and regulation of metabolism (direct effects of GH)

A
  1. increase gluconeogenesis by liver
  2. reduce ability of insulin to stimulate glucose uptake by muscle and adipose tissue
  3. makes adipocytes more sensitive to lipolytic stimuli
  4. inc amino acid uptake and protein synthesis in almost all cells
17
Q

how is GH diabetogenic

A

GH releases energy stores to support growth

it is having an anti-insulin effect and increases blood glucose

18
Q

summart direct effects of GH

A
  • mobilise Glc stores to inc blood glc
  • inhibit action insulin
  • promotes lipolysis - providing source of energy for most cells and so sparing Gcl
  • promotes amino acid uptake into cells, supporting protien synthesis
19
Q

stimuli that increase GHRH secretion

A
  • actual or potential drop in energy supply to cells
  • inc amounts of amino acids in plasma
  • physical stress and illness
  • delta sleep
  • oestrogen and testosterone
20
Q

stimuli that increase GHIH (somatosatin release)

A
  • glucose
  • FFA
  • REM sleep
  • cortisol
21
Q

physiology of growth - complex phenomenon affected by 3 factors…

A

hormones
nutrition
genetics

22
Q

physiology of growth - hormones

A 
GH 
IGF-1
thyroid hormones
sex steroids
glucocorticoids
insulin
23
Q

thyroid hormones and growth

A

essential for growth, esp developent nervous system in utero and early childhood

effects are permissive to GH/IGF-1

24
Q

physiology of growth - nutrition

A

adequate diet - protein content, essential vitamins + minerals very important

injury and disease stunt growth because increase protien catabolism

25
Q

physiology of growth - genetic factors

A

helps determine maximum growth

interaction between genetic factors and nutrition

26
Q

2 periods of rapid growth

A

infancy

puberty

27
Q

puberty growth

A

due to androgens and oestrogens, produce spikes in GH secretion

promote bone elongation - inc height, weight and body mass

sex hormones at later stage of puberty act o close epiphses and so stop bone elongation

28
Q

gigantism

A

excess GH due to pituitary tumour before epiphyseal plates close

excessive growth 1

29
Q

acromegaly

A

excess GH due to pituitary tumour after ephyseal plates have sealed

no longutidinal growth but can grow in oher directins
characteristically enlarged hands and feet

endocrine (19 decks)

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