Growth

Question 1

Structure of Growth hormone

Answer 1

191 Amino acids in length, a very large protein hormone

Question 2

Somatomammatropin family

Answer 2

3 hormones with sequence homology
Human placental lactogen (hPL) is produced by the placenta and may have some growth hormone like effect in pregnant women

Prolactin and growth hormone have sequence homology, but they usually dont bind to each others receptors

Question 3

Direct effects of Human growth hormone

Answer 3

Adipose tissue: decrease glucose uptake, increase lipolysis, decrease adiposity

Liver: increase gluconeogenisis, increase (IGF1)

Muscle: decrease glucose uptake, increase AA uptake, increase protein synthesis, increase lean body mass

Question 4

Indirect effects of human growth hormone

Answer 4

All caused by IGF-1

BONE/HEART/LUNGS: increase protein synthesis, increase DNA and RNA expression, increase in cell size and number, increase in organ size and function

Chondrocytes: increase amino acid uptake, increase protein synthesis, increase DNA and RNA expression, increase collagen, increase linear growth

Question 5

Hormonal control of growth from conception to adulthood

Answer 5

Fetal: fetal insulin, a little growth hormone, MATERNAL THYROID HORMONE is important for first trimester of pregnancy

Childhood: thyroid hormone

Pubertal growth: sex steroids from testes or ovaries have 2 major effects: activation of pubertal growth spurt via stimulation of growth hormone release, terminates pubertal growth via closure of epiphyseal plates in long bones

normal growth from 2-puberty (GH)
growth spurt (Sex steroids)

Question 6

Regulation of Growth hormone

Answer 6

Stimulation: Amino Acids, Hypoglycia, exercise, stage 3 and 4 sleep, gonadal steroids, thyroid hormone

Inhibition: Glucose (negative feedback), Growth hormone (short loop), IGF-1 (negative feedback), Cortisol

Question 7

Control loops of GH

Answer 7

Higher brain centers tell hypothalamus to secrete GHRH (activation) or SST (somatostatin, inhibitory)

These either stimulate or inhibit the pituitary to release growth hormone

Growth hormone stimulates target tissue (liver) an makes IGF-1

GH will inhibit GHRH, and IGF will inhibit GH release and stimulate SST

Question 8

Disorders of Growth hormone

Answer 8

Too much- due to pituitary secreting GH
Before puberty- gigantism
After puberty-acromegaly

Too little- GH deficiency
Children- short
Adults- controversial

Question 9

Glucocorticoids and Growth hormone

Answer 9

Hypothalamus: GC stimulate SST and inhibit GHRH
Pituitary: GC inhibit pulsatile GH release
Bone: GC inhibits response to IGF1 and collagen syn
Men: GC inhibits GnRH/ LH/FSH in men