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PHYL2064 > Endocrine L2: Endocrinology Growth > Flashcards

Endocrine L2: Endocrinology Growth Flashcards

1
Q

What are 3 structural processes growth of tissues?

A
  1. Synthesis of proteins
  2. Lengthening of long bones
  3. Soft tissue cell size & number increase
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2
Q

Growth is ____ (linear/angular).

A

linear

  • Highest in utero, then two major growth spurts during life
    • During early years (toddler) and during puberty
  • Occurs primarily through the actions Occurs primarily through the actions of Growth Hormone
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3
Q

What are 4 extent of growth influenced by (growth hormone)?

A
  1. Genetic determination of height & shape
  2. Dietary impact – especially amino acids
    • Proteins (eg. child with protein = won’t grow as tall or if they have ever been starved = won’t reach full growing capacity)
  3. Chronic disease or stressful environment (Stress (cortisol impairs growth) or Type I Diabetes)
  4. Other hormones influencing growth – thyroid hormone, insulin, sex steroids
    • During puberty
      • Also decrease growth as it closes the epiphyses
      • Males are taller than females. Why?
        • Testosterone closes bone epiphyses slower than estrogen does )
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4
Q

What are 4 characteristics of the growth hormone (GH, somatotrophin)

A
  1. 191 amino acid single chain polypeptide
  2. Binds to specific GH -receptors on tissue
  3. Some GH is bound to carrier protein in plasma so amount of GH-BP influences circulating levels
  4. Half binding proteins 50% Free proteins 50% GH = hydrophilic (dissolves in the blood)
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5
Q

What does the control of synthesis and release for growth hormone?

A
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6
Q

GH secretion is _____. What does it mean?

A

pulsatile

Plasma levels high in neonate, decrease in childhood, rise again at puberty, then fall during adulthood

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7
Q

What are the 2 overall actions of GH?

A
  1. Anabolic (true) growth
  2. Metabolic (distinct from growth)
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8
Q

What are the 2 changes in anabolic (true) growth as a result of GH?

A
  1. ncreases thickness & length of long bones
  2. Increases size & number of cells in soft tissue
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9
Q

What are the 2 changes in metabolic (distinct from growth) as a result of GH?

A
  1. Increases fat breakdown/increases circulating fatty acids circulating fatty acids
  2. Decreases glucose uptake by muscles
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10
Q

What is the classic view of GH?

A
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11
Q

What are now 5 known things about GH?

A
  1. GH-receptor found in most tissues so -
  2. some effects are IGFs from liver some are direct effects
  3. some are direct effects of GH in target tissue
  4. some are due to local Promotion some are due to local release of IGFs
  5. some are due to local production of GH in target tissues
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12
Q

What are 3 direct GH actions via a GH-receptor in regards to muscles? What is the effect?

A
  1. stimulates amino acid uptake (More protein)
  2. decreases glucose uptake
  3. inhibits protein breakdown = increase muscle mass
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13
Q

What are 2 direct GH actions via a GH-receptor in regards to adipose (fat) tissue? What is the effect?

A
  1. decreases glucose uptake
  2. increases fat breakdown (lipolysis) = decrease in fat deposits decrease in fat deposits
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14
Q

What are 2 direct GH actions via a GH-receptor in regards to liver? What is the effect?

A
  1. increases protein synthesis increases protein synthesis
  2. increases gluconeogenesis = increase metabolism increase metabolism
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15
Q

What are 3 indirect mediated GH action by somatomedins (IGFs) for IGF-I?

A
  1. causes proliferation of chondrocytes (cartilage cells) at epiphyseal plates increasing g bone length
  2. stimulates osteoblast activity to produce organic matrix increasing bone thickness (Helps to lay down the calcium carbonate crystals –> mineralisation of bones)
  3. promotes soft tissue growth through hyperplasia (increased number of cells) and hypertrophy (increased size of cells) (increased size of cells)
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16
Q

What is an indirect mediated GH action by somatomedins (IGFs) for IGF-II?

A

promotes soft tissue & organ growth by increasing protein, RNA & DNA synthesis

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17
Q

In general GH acts to redistribute _____ towards ______ such as growth

A

nutrients; production processes

18
Q

A growing person/child has _____ (open/closed) epiphyses.

A

open

19
Q

An adult has _____ (open/closed) epiphyses.

A

closed

20
Q

GH causes ____ growth and _____ effects

A

true; metabolic

21
Q

What are 3 changes in GH for true growth and metabolic effect?

A
  1. increases blood glucose
  2. stimulates lipolysis stimulates protein synthesis
  3. decreases protein catabolism
22
Q

What are 4 influences of synthesis and release of GH by other hormones?

A
  1. Thyroid hormones – permissive
    • As long as enough = will growth BUT if have more = won’t grow more
    • low TH = low growth
  2. Glucocorticoids (Stress hormone) – excess inhibits growth
  3. Sex steroids – synergistic, androgens important for pubertal growth spurt, but ultimately promote closure of epiphyses of epiphyses
  4. Insulin – deficiency = low growth, excess = higher growth
23
Q

What is gigantism caused by?

A

GH hypersecretion in children

Abnormally tall 2.4 m

Normal body proportions (soft tissues also affected)

24
Q

What is the abnormality for GH hypersecretion in adult?

A

acromegaly

Different effect than when there is excess as a child

25
Q

What are 3 characteristics of GH excess (acromegaly)?

A
  1. Enlarged extremities: bones in hands, feet and face
  2. Thickening soft tissues leads to coarse or malformed facial features enlarged tongue thickened lips deep facial features, enlarged tongue, thickened lips, deep voice, sleep apnoea (Can’t sleep properly), cardiomegaly (No increase in functionality only mass), degenerative arthropathy, muscle hypertrophy but weakness, Poor exercise capacity
  3. Usually due to pituitary tumour, Compression OR can be due to GH abuse
26
Q

What happens in acromegaly?

A

Don’t get taller (epiphyses closed) but influence bone density

27
Q

How do people with acromegaly usually die?

A

Defect in heart function (as there is increase) mass= kills people with acromegaly

28
Q

What is the abnormality for GH hyposecretion in adult?

A

No major symptoms

Lowering of muscle mass, increase in fat and faster loss of bone density –> not very noticeable

29
Q

What is the abnormality for GH hyposecretion in children?

A

“pituitary dwarfism”

30
Q

What are 4 characteristics of “pituitary dwarfism”?

A
  1. Usually lack GH or GHRH, but other types possible (From failure of pituitary gland to produce GH)
  2. Short stature = max 1.2m
  3. Normal body proportions body proportions
  4. Poor muscle development, excess subcutaneous fat
31
Q

If Pituitary dwarfism is diagnosed before puberty, _______ gives near normal growth. Why is this important for babies to get checked up?

A

replacement therapy (recombinant hGH)

That’s why babies are constantly checked to observe normal growth (normal growth patterns)

32
Q

Why is replacement therapy (recombinant hGH) only effective in children before puberty?

A

Before epiphyses close

33
Q

How does testosterone affect GH?

A
34
Q

What are 5 characteristics of the elixir of youth- recombinant hGH?

A
  1. Aging: loss of lean muscle mass, increased fat deposits, loss of bone density, declining GH levels
  2. As GH has effects on muscle mass, fat deposits & bone density can it reverse effects of aging? bone density, can it reverse effects of aging?
  3. Early studies with injected hGH (In elderly) showed increased muscle decreased fat BUT no effect on bone muscle, decreased fat… BUT no effect on bone density, muscle strength or exercise capacity… AND had potential for serious side-effects
  4. Improved exercise regimen also showed increased muscle, decreased fat… AND better exercise capacity
  5. Addition of hGH to exercise had no added benefit over placebo
35
Q

Why must GH be injected not ingested?

A

If ingested will be broken down as it is protein

36
Q

What was the conclusion for the exlixir of youth- recombinant hGH?

A

GH has not benefits (doesn’t work) = it was the exercise that was effective

Might be because if injected with artificial hormone, body stops producing normal hormone level

37
Q

What occurs during ageing in terms of GH?

A

Aging: loss of lean muscle mass, increased fat deposits, loss of bone density, declining GH levels

38
Q

As GH has effects on muscle mass, fat deposits & bone density can it reverse effects of aging?

A

GH has not benefits (doesn’t work) = it was the exercise that was effective

Might be because if injected with artificial hormone, body stops producing normal hormone level

39
Q

Early studies with injected hGH showed increased muscle decreased fat BUT no effect on ____, ____ or _____ capacity… AND had potential for serious side-effects

A

bone density, muscle strength or exercise

40
Q

Since hGH is so expensive what do athletes sometimes do?

A

sometimes use equine growth hormone (horse) = similar

PHYL2064 (29 decks)

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