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Flashcards in Human Growth Deck (58):
1

What are the four stages of growth?

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

2

What occurs in hypothyroid dwarfs (cretins)?

They retain their infantile proportions

3

What occurs in hypopituitary dwarfs?

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

4

What are the two periods of rapid growth?

Infant growth
Pubertal growth spurt

5

What is infant growth?

A continuation of the rapid fetal growth period

6

What is pubertal growth spurt due to?

GH
Androgens
Estrogens

7

What sex does puberty occur first?

Females

8

When does the pubertal growth spurt cease?

Closure of the epiphyseal plates in long bones by estrogen

9

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

Linear and mass growth

10

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

Good nutrition: 80% genetics
Poor nutrition: 60% genetics

11

What occurs in long bone growth?

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

12

What does estrogen cause in chondrocytes?

Increase apoptosis of chondrocytes thus closing of epiphyseal plates

13

What do glucocorticoids cause?

Slows chondrocytes proliferation process inhibiting growth

14

What is the "catch up" affect?

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

15

What nuclei produce SST?

Ventromedial
Paraventricular

16

What nuclei produce GHRH?

Paraventricular
Arcuate

17

What does GHRH cause?

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

18

What does SST cause?

Acts on somatotrophs via G alpha i inhibiting GH release

19

What is the dominant form of GH released?

22 kDa

20

What is GH synthesized as?

Preprohormone

21

How is the secretion of GHRH and GH described?

Pulsatile

22

When is the largest pulse of GHRH and GH secreted?

During sleep

23

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

IGF-1

24

What catabolic affects does GH have?

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