endocrinology lecture 5

Question 1

what are the non-endocrine factors that regulate growth

Answer 1

1. genetics

2. nutrition

Question 2

what does disease do to tissues

Answer 2

damages tissues and activated HPA axis (hypothlamus, pituitary, adrenal)

Question 3

what are the 3 hormones of the growth axis

Answer 3

GHRH (hypothalamus), GH (ant. pituitary), IGF-1 (liver)

Question 4

IGF-1 is most necessary for what kind of growth

Answer 4

fetal growth (GH becomes important later in development)

Question 5

how does thyroid hormone affect GH

Answer 5

TH is required for:

1. GH synthesis (bc decreased TH causes stunted growth)
2. GH effects (bc TH regulates metabolism, or ATP production, that GH uses to build tissue)

Question 6

effect of glucocorticoids on growth

Answer 6

glucocorticoids inhibit GHRH secretion from the hypothalamus

Question 7

what is the effect of insulin on growth

Answer 7

insulin opposes GH and IGF-1 (insulin stores glc and GH/IGF-1 liberates glc for use)

Question 8

effect of GH on bone growth

Answer 8

since bone growth consists of cartilage placed first (and then replaced by bone to grow), GH:

1. causes chondroblasts to be converted to condrocytes (chondroblast maturation)
2. increases IGF-1 receptors in chondrocytes so IGF can stimulate cell replication and therefore growth

Question 9

effect of E2 on bone growth

Answer 9

E2 causes the epiphyseal plates to ossify at puberty

bc E2 stimulates osteoblast activity (causing an increase in the rate at which cartilage–> bone)

Question 10

why are men taller?

Answer 10

although males and females have the same change in height, females start puberty earlier and therefore start out smaller.

Question 11

what are the 2 hypothalamic hormones that regulate growth

Answer 11

1. GHRH

2. Somatostatin

Question 12

GH is a ______

Answer 12

mitogen (stimulates cell division)

Question 13

what does GH do in somatic tissue (muscle/bone) that is independent of IGF-1

Answer 13

increase protein synthesis

Question 14

princible effect of GH

Answer 14

stimulate the secretion of IGF-1 from liver and other tissues

Question 15

IGF-1 and GH inhibit

Answer 15

GH (short loop) and GHRH (long loop)

Question 16

IGF-1 and GH stimulate

Answer 16

SS (from ant pituitary)

Question 17

GHRH is elevated during

Answer 17

sleep…grow when you sleep! (diurnal/cicadian pattern)

Question 18

SS is elevated during

Answer 18

day (diurnal/cicadian pattern)

Question 19

in summary, what are the 3 major effects of GH

Answer 19

1. promotes growth (via IGF-1)
2. protein synthesis (in bone and muscle)
3. anti-insulin (create higher blood glc levels)

Question 20

deficits of IGF-1 and GH lead to

Answer 20

reduced growth as a result of genetic mutations or malnutrition

Question 21

are there known defects of IGF-1 synthesis and IGF-receptors?

Answer 21

no

Question 22

what is the effect of malnutrition on growth

Answer 22

malnutrition impairs IGF-1 synthesis INDEPENDENT of GH

Question 23

how is GH production affected

Answer 23

age. GH is highest during adolescence and lowest during adulthood (don’t grow much as an adult)

Question 24

sex steroid (E2 and P) regulate growth by….

Answer 24

1. stimulating GH and IGF-1 synthesis
2. cause pre-pubertal bone growth spurt
3. ultimately cause fusion of epiphyseal plates which then inhibits growth (contrasting effect)

Question 25

excess GH production causes

Answer 25

1. acromegaly | 2. gigantism

Question 26

acromegaly and gigantism (due to excess GH) are typically caused by what

Answer 26

a pituitary tumor (where GH is secreted from)

Question 27

Gigantism is a result of what

Answer 27

pre-pubertal excess GH

Question 28

acromegaly is a result of what

Answer 28

post-pubertal excess GH

Question 29

effects of excess GH

Answer 29

- diabetic like (bc increase circulating blood glc) | - macroglossia, increased teeth spacing, big salivary glands, excess cementum

Question 30

GH insufficiency causes what

Answer 30

reduced growth...treated with exogenous GH

Question 31

dwarfism is a result of what

Answer 31

GH insensitivity due to absence of GH receptor

Question 32

dwarfism is treated with

Answer 32

exogenous IGF-1

Question 33

symptoms of dwarfism

Answer 33

...i mean you would probably know if you had it but you may also be obese. you wouldn't have diabetes or cancer though!

Question 34

what is achondroplasia

Answer 34

reduced growth dues to constant activation of the fibroblast growth factor receptor. bc FGF normally inhibits bone growth. so constant activation results in impaired development of cartilage

Question 35

effects of too little GH/GH insufficiency

Answer 35

- delayed tooth shedding/replacement - decreased saliva - increase P.D and caries

Question 36

diabetes is fatal when

Answer 36

leads to ketoacidosis

Question 37

symptoms of diabetes

Answer 37

1. dehydration (and therefore reduced saliva) 2. increased urine 3. acidosis 4. decreased immune (bc increased cortisol) 5. stress (increased cortisol)