Human Growth Flashcards

(58 cards)

1
Q

What are the four stages of growth?

A
  1. ) Intrauterine
  2. ) Postnatal
  3. ) Pubertal
  4. ) Adult growth/senescence
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2
Q

What occurs in hypothyroid dwarfs (cretins)?

A

They retain their infantile proportions

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3
Q

What occurs in hypopituitary dwarfs?

A

They have proportions similar to their chronological age until puberty; do not mature sexually so they have juvenile features as adults

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4
Q

What are the two periods of rapid growth?

A

Infant growth

Pubertal growth spurt

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5
Q

What is infant growth?

A

A continuation of the rapid fetal growth period

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6
Q

What is pubertal growth spurt due to?

A

GH
Androgens
Estrogens

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7
Q

What sex does puberty occur first?

A

Females

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8
Q

When does the pubertal growth spurt cease?

A

Closure of the epiphyseal plates in long bones by estrogen

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9
Q

What are the two types of growth involved in human growth?

A

Linear and mass growth

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10
Q

What percentage does genetics play into growth with good nutrition and poor nutrition respectively?

A

Good nutrition: 80% genetics

Poor nutrition: 60% genetics

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11
Q

What occurs in long bone growth?

A

Chondrocytes in the epiphyseal growth plates begin to proliferate and create more cartilage that then is calcified to bone

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12
Q

What does estrogen cause in chondrocytes?

A

Increase apoptosis of chondrocytes thus closing of epiphyseal plates

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13
Q

What do glucocorticoids cause?

A

Slows chondrocytes proliferation process inhibiting growth

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14
Q

What is the “catch up” affect?

A

High glucocorticoids such as chronic stress, illness, or therapy can cause slowing of growth but once the glucocorticoids are removed the chondrocytes proliferate rapidly to catch up to what their normal rate would be

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15
Q

What nuclei produce SST?

A

Ventromedial

Paraventricular

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16
Q

What nuclei produce GHRH?

A

Paraventricular

Arcuate

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17
Q

What does GHRH cause?

A

Acts on somatotrophs via G alpha s increasing GH synthesis and release

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18
Q

What does SST cause?

A

Acts on somatotrophs via G alpha i inhibiting GH release

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19
Q

What is the dominant form of GH released?

A

22 kDa

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20
Q

What is GH synthesized as?

A

Preprohormone

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21
Q

How is the secretion of GHRH and GH described?

A

Pulsatile

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22
Q

When is the largest pulse of GHRH and GH secreted?

A

During sleep

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23
Q

What does GH release from effector cells via a JAK STAT receptor?

A

IGF-1

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24
Q

What catabolic affects does GH have?

A

Decrease cell uptake of glucose and fat (hyperglycemic)

Mobilize fats by increasing hormone sensitive lipase

25
What are the direct anabolic effects of GH?
Increased uptake of AA by cells
26
How are indirect anabolic effects of GH mediated?
IGF-1
27
GH stimulates the liver and other tissues to secrete IGF-1, how does IGF-1 mediate its effects on growth?
IGF-1 stimulates proliferation of chondrocytes
28
IGF-I effect on protein metabolism?
Protein anabolism Increased amino acid uptake Increased protein synthesis and decreased oxidation of proteins
29
GH effect on fat metabolism?
Enhances utilization of fat by stimulating lipolysis
30
GH effect on carbohydrate metabolism?
Maintain blood glucose within normal range
31
How does GH maintain blood glucose within normal range?
It has anti-insulin activity as it suppresses the abilities of insulin to stimulate uptake of glucose in peripheral tissues
32
Main effect of GH on muscle?
Decrease glucose uptake
33
Main effect of GH on fat?
Increased lipolysis
34
Main effect of GH on liver?
Increased gluconeogenesis
35
Four negative feedback regulations of GH/IGF-1?
1. ) Directly inhibits somatotrophs 2. ) Suppress GHRH in Arcuate nucleus 3. ) Increases SS secretion in PEV nucleus 4. ) GH inhibits itself
36
What has a positive feedback on GH?
Ghrelin
37
How does 40% of GH circulate in the blood?
Bound to GH binding protein (GHBP)
38
What occurs in congenital GH deficiency?
Growth rate decreases after birth | High plasma lipid profile (lack of lipolytic activity to break down lipids)
39
What occurs in acquired GH deficiency?
Onset late childhood or adolescence | Pituitary hormone deficiencies
40
What occurs in Laron syndrome?
GH receptor disorder or post-receptor defect | Short stature
41
What do Pigmies have?
Normal GH and IGF-II Low IGF-I Cannot produce IGF-I
42
When does IGF-II play a big role in development?
Early in pregnancy
43
Three ways IGF-1 inhibits GH?
1. ) Direct inhibition of somatotrophs 2. ) Suppress GHRH in Arcuate nucleus 3. ) Increase SS secretion in the PVN/PEV
44
What hormones are central to in utero/early childhood, postnatal/pubertal, and terminating linear growth?
In utero/early childhood: Thyroid hormones Postnatal/pubertal: GH and IGF-I Terminating linear: Androgens and estrogen
45
What is the major role of IGF-II?
Growth promoting during gestation
46
What creates IGF-II?
Thecal cells
47
During gestation what are two ways IGF-II works as a hormone?
Autocrine: on Thecal cells Paracrine: on Granulosa cells
48
What does IGF-II do during follicular phase?
Works alongside FSH to promote follicle stimulation
49
What does IGF-II do during luteal phase?
Promotes progesterone secretion working with LH
50
What affect does insulin have on growth?
Same as IGF-I | Mothers with hyperinsulinemia have higher child birth weights
51
What are the effects of T3 in developing children and adulthood?
Developing childhood: Required for skeletal development during childhood Adults: regulates bone turnover and mineralization
52
What is the effect of thyrotoxicosis in adult bone growth?
Increased risk for osteoporosis
53
What effect does pregnancy have on thyroid hormone?
estrogen stimulate an increased T4 binding globulin leading to a lower level of free T4 resulting in elevated TSH and thyroid hormones being produced; ultimately. you need a large amount of iodine intake during pregnancy
54
What are the effects of excess sex steroids before puberty?
Increase in linear growth rate but the epiphyseal plate closes faster leading to an overall decrease in final linear growth
55
What causes acromegaly?
Excess anterior pituitary production of GH after epiphyseal plate closure
56
What is fetal macrosomy?
A newborn significantly larger than average
57
What is the average calorie expenditure for a normal 70 kg person?
2800 Kcal/day
58
How many calories are in one pound of fat?
4200 Kcal