Chapter: Endocrine Control of GH Flashcards

1
Q

GH is children causes

A
  • a continuous net protein synthesis
  • increase in lenght, diameter, size, and the number of cells in the soft tissues and long bones
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2
Q

Characteristics of fetal growth

A
  • GH from the fetal pituitary plays NO role in fetal growth (growth facilitated by placenta hormones)
  • genetic and nutritional factors effect fetal growth
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3
Q

postnat growth occurs

A

during the first 2 years of life

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4
Q

pubertal growth occurs

A

during adolescent

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5
Q

Secretion of ______ during pubertal growth increases protein synthesis and bone growth

A

androgen

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6
Q

a marked acceleration in _______________ is due to lengthening of long bones

A

linear growth

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7
Q

________ promotes protein synthesis and bone growth in pubertal boys

A

testosterone

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8
Q

what 2 hormones act on the bones to achieve full adult height by the end of adolescence

A

testosterone and estrogen

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9
Q

what are the 4 factors affecting growth

A
  • genetic factors
  • an adequate diet
  • free chronic diseases and stress
  • normal level of GH hormones
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10
Q

genetic factors

A

determine an individuals maximum growth

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11
Q

adequate diet

A
  • protein and amino acid rich diet
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12
Q

an inadequate diet in infancy and childhood can causes

A

stuning in brain and growth development

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13
Q

___% of total growth occurs in the first 2 years of life

A

70

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14
Q

effect of chronic diseases and stress on growth

A
  • cortisol acts as an anti-growth hormone by protein breakdown (protein degration), inhibiting the growth of long bones and GH secretion
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15
Q

what other hormones effect GH secretion

A

thyroid, sex hormones, and insulin

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16
Q

bone thickness

A
  • achieved by adding new bone cells by osteoblast tot the periosteum (bones outer surface)
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17
Q

Bone growth (linear growth)

A
  • caused by division (proliferation) and multiplication of chondrocytes on the outer edge of the epiphyseal plate
  • enlargement of chondrocytes in the diaphysis widens the epiphyseal plate
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18
Q

4 metabolic effects of GH

A
  • increases the rate of protein synthesis
  • increased fatty acid mobilization by adipose tissue degration and increases fatty acid use by the body
  • decrease rate of glucose uptake by body tissues (increases blood glucose levels)
  • increase glucose output by the liver
19
Q

GH promotes the growth of soft tissues and the skeleton by,

A
  • hyperplasia
  • hypertrophy
20
Q

hyperplasia

A

increases the number of cells

21
Q

hypertrophy

A

increases the size of cells

22
Q

Growth promoting actions of GH on soft tissues

A
  • increases size of cells by cell division
  • prevents apoptosis (programmed cell death)
  • increases protein synthesis (uptake amino acids by cells)
  • stimulates the cellular machinery according to genetic code to accomplish protein synthesis
23
Q

feedback of GH

A

Negative feedback

hypothalamus –> hypophysiotrophic hormones (GHRH/GHIH)–> anterior pituitary –> target tissues/endocrine gland

24
Q

Somatomedin / insulin-like growth factor (IGF-1)

A
  • acts directly on bones and soft tissues to bring about most growth promoting actions
  • stimulates protein synthesis, cell division, lengthening, and thickening of bones
  • increases fatty acid levels in the blood by enhancing triglyceride / fat storage breakdown in the adipose tissue
  • increases blood glucose levels by decreasing glucose uptake by muscles
25
IGF-2 functions
- does not depend on GH level - important in fetal development - role in adults is unclear
26
what are the 3 factors that control IGF-1 production
- nutrition - age - various tissue-specific stimulating factors
27
nutrition effect on IGF-1
- inadequate food intakw decreases IGF-1 levels through sensitivity to GH in the tissue that produces IGF-1 - EXAMPLE: fasting decreases IGF-1 levels but increases GH secretion
28
Age effect on IGF-1
a dramatic increase in circulating IGF-1 levels accompanies the moderate increase in GH at puberty
29
various tissue specific stimulating facts effect on IGF-1
- increase IGF-1 production in a particular tissue
30
Example on how various tissue specific stimulating facts effects IGF-1
gonadatropin and sex hormones stimulate IGF-1 in the testes, the ovaries and the uterus (fetal development)
31
What are the 4 factors that influence GH secretion
- GHRH/GHIH - Diurnal rhythms - excercise, stress, and hypoglycemia - amino acids
32
GHRH/GHIH effect on Gh secretion
- antagonistic factors that control GH secretion - negative feedback loop - somatomedins (liver) influence the anterior pituitary to inhibit the effects of GHRH an Gh release
33
Diurnal rhythms effect on GH secretion
- GH levels tend to be low and constant for most of the day - Gh levels are 5 times higher after one hour of deep sleep and drops over several hours throughout the day
34
Amino acids effect on GH secretion
- increasing the amino acid level after a high protein meal increases GH secretion - a decrease in blood fatty acid stimulates GH release
35
cause of dwarfism
- lack of GH from the anterior pituitary in a child - lack of growth hormone-releasing hormones from the hypothalmus
36
Dwarfism symptoms
- hyposecretion of GH in childhood - poorly developed musculature - excessive subcutaneous fat (less fat mobalized)
37
Laron Dwarfism
- failure of tissue to respond to GH (receptors are unresponsive) - reduced skeletal muscle mass and decreased bone density in adults - risk of developing heart failure
38
Gigantism
- tumor of GH producing cells in the anterior pituitary - overproduction of GH in childhood before the epiphyseal plate closes - individual may reach a high of 8ft or more
39
Acromegaly casues
- hypersecretion of GH after adolescence before the epiphyseal plate close, further growth in height is prevented
40
Acromegaly symptoms
- thickening of soft tissues (skin and bones become thick in the extremities and face) - jaw and cheekbone can fuse, giving ape-like appearance - hands and feet enlarge, and fingers and toes become thick - peripheral nerve disorder may occur from overgrown connective tissues that trap nerves - may result in visual disturbances
41
thyroid hormone role in growth
- essential for normal growth but does not promote growth - plays a permissive role in skeletal growth
42
children whom experience hypothryroidism exhibit
stunted growth
43
insulin effect on growth
- serves as a growth promotor - Hyperinsulinemia increases growth and deficiency reverses it - it may excert its effects via IGF-1 receptors as both receptors appear to be similar structurally
44
Androgens (testosterone and estrogen) effect on growth
- powerfully stimulate protein synthesis - promotes linear growth, body weight and muscle mass - testicular androgen developes heavier musculature in males - androgenic growth promoting effects are exerted through GH - estrogen terminates linear growth by stimulating the conversion of the epiphyseal plate to bone