Growth hormone Flashcards
Factors that control the growth of the brain, Gonads, and the body?
Brain: neurotrophic factors
Gonads: gonadotropins -> LH and FSH
Body: somatotropin
Where are growth hormones produced?
The pituitary gland, the brain determines the amount of produced hormones -> distributed through blood
Explain the structure of a growth hormone
4 alpha helices and 2 disulfide bonds (from Cysteine!!)
When during the day is GH secreted?
It follows a daily circadian rhythm, peeking early at night time during !deep sleep! in children and young adults
Explain sexual dimorphism related to GH?
males: pulse often more frequent with higher amplitude
female: higher through the level (baseline) with similar amplitude, but greater total GH area under the curve
How important is the pulsatile secretion of GH and how is it controlled?
pulsatile secretion leads to more growth shown in mouse experiment,
stimulated by GH-releasing hormone
inhibited by SRIH somatotropin releasing inhibiting hormone
Name the only hormone that is regulated positively and negatively
GH, (+) by GHRH (-) by Somatostatin
Explain neuroendocrine regulation
arcuate nucleus (ARC) contains GHRH neurons
anterior periventricular nucleus (PeN) contains SS
-> transported through Hypothalamo-pituitary portal vessel
Explain the pulsatility of GH secretion
It is based on switching ON and OFF GHRH and Somatostatin
Where and what are the effects of GH in the body?
- Liver: secretion of IGF-1
- organs and tissues: protein synthesis, carbohydrate and lipid metabolism
Explain the direct and indirect effects of GH
direct: GH binds to GH receptor on liver, muscles, adipose tissue,..
and stimulate metabolic activity
indirect effects through secreted IGF´s
How do long bones grow?
GH stimulates cell division of osteoblasts and chondrocytes in the Epihysial growth plate
When and how is bone growth regulated?
The increase of hormones of maturing gonads leads to epiphysial closure
–> closed plates cant respond to GH
Anabolic and catabolic effects of GH
Liver: catabolic production of energy to fuel -> anabolic production of proteins, etc + make IGF´s work on other tissues
Bone: cell division to increase the size and anabolic biosynthesis (DNA, proteins, cell membrane) to make growth possible
Adipose tissue: catabolic production of energy to fuel anabolic reactions
What causes giantism?
Excess of GH, in case of Alton giant: pituitary tumor of GH producing cells (somatroph)
