6 integrated endocrine physiology

Question 1

define synergistic

Answer 1

produce greater enhanced response than sum of either hormones alone

Question 2

define permissive

Answer 2

presence of one hormone allows second hormone to act

Question 3

define antagonistic

Answer 3

effects of hormones oppose each other

Question 4

what are four factors that affect growth?

Answer 4

1. genetics
2. socioeconomic and nutritional
3. chronic disease and stress
4. endocrine hormones (mainly GH)

Question 5

describe direct action of GH

Answer 5

1. direct: metabolism
   - GH and cortisol antagonistic to insulin
   - increases blood glucose
   - anti insulin and diabetogenic

Question 6

indirect action of GH

Answer 6

• Stimulate release of growth factors such as IGF I & IGF II (somatomedins) from liver and other cells
• growth via IGF I on cells
  
  • protein synthesis, hypertrophy (cell size)-> increase lean body mass
  • cell division, hyperplasia (cell number)-> increase in organ size
  • skeletal growth-> linear growth (height)
    
    • enhances chrondocyte proliferation and differentiation

Question 7

what other hormone is required for GH action on growth?

Answer 7

thyroid hormones- permissive role, key in CNS development

Question 8

what are other important hormones for growth except GH and thyroid?

Answer 8

insulin: anabolic, intra uterine-growth factor, stimulates protein synth

sex hormones: muscle building, stops bone elongation by promoting epiphyseal plate closure

Question 9

Answer 9

Question 10

what is the effect of anterior pituitary hormones on tissue growth?

prolactin

gonadatrophins

TSH

ACTH

Answer 10

influences selective tissue growth- trophic effect

breast

testes, ovaries

thyroid

adrenal cortex

Question 11

what are non- specific potent stimuli for GH secretion?

Answer 11

sleep, stress, exercise

Question 12

Answer 12

Question 13

when is the peak secretion of GH?

Answer 13

an hour after sleep

(70% total daily GH released in sleep)

Question 14

what is the relationship between glucocorticoids and GH?

Answer 14

synergistic, Mobilise reserves, increase availability of glucose

but chronic high [glucocorticoids] inhibit GH release

eg. Cushing’s disease, long term use steroids

Question 15

what are the effects on metabolism of cortisol and GH?

Answer 15

both: increase lipolysis and gluconeogenesis

cortisol increases protein breakdown

GH increases AA uptake and protein synthesis

Question 16

what is the lifetime pattern of GH secretion?

Answer 16

high in childhood, peak in puberty

lower concentrations in adult

Question 17

symptoms of GH deficiency in adults

Answer 17

• Psychological changes
• Malaise, excessive tiredness, anxiety and depression
• Osteoporosis
• Poor muscular tone, decrease in lean body mass
• Impaired hair growth
• Increase in adipose tissue (especially around the waist)

Question 18

what is sexual precocity?

Answer 18

Initial accelerated bone growth

(early growth spurt)

Question 19

what is Eunuchoidism

Answer 19

(lack of GnRH and hypogonadism-> low sex hormone levels result in extension of long bone growth)