Physiology of Growth Flashcards
Where is growth hormone released from?
Anterior pituitary
What is growth hormone’s function?
promotes growth by stimulating cell proliferation
What is GH otherwise known as ?
Somatotrophin
What type of hormone is growth hormone?
Peptide hormone
How does growth hormone circulate the blood?
Unusually, 60% circulates bound to a carrier protein
What permissive actions does growth hormone require?
The action of thyroid hormones and insulin before it can stimulate growth
What is it’s half life?
12 minutes
What is a somatopause?
GH levels drop significantly in the elderly
What is IGF-1?
Intermediate of GH that is secreted by the liver in response to GH release from the anterior pituitary, and IGF-1 controls GH release through a negative feedback loop.
What effect does GH have on bones?
Stimulates the precursor cells of chondrocytes in the epiphyseal plates which when matured produce collage which thickens and calcifies and then allows osteoblasts to lay down new bone
Which hormone does GH mimic?
Glucagon
Describe 4 effects of growth hormone
Increases gluconeogenesis in the liver
Reduces glucose uptake by suppressing insulin
Makes adipocytes more sensitive to lipolysis
Increases amino acid uptake and protein synthesis
What hormone controls the release of growth hormone?
GHRH
What is the mean average of growth hormone in the blood?
2-4ng/ml in adults
5-8ng/ml in children and through puberty
At what point through the day of a child is growth hormone most released?
During deep sleep
What stimuli increase GHRH?
Increased amino acids in the blood
Stressful stimuli - usually counteracted by cortisol
Deep sleep
Oestrogen and androgens
Name stimuli that increase GHIH
Glucose
Cortisol
FFA
REM sleep
What are the 3 factors that affect out growth?
Hormones
Nutrition
Genetic factors
What are the two rapid period of growth?
Infancy and puberty
What is the cause of giantism?
Extra growth hormone due to pituitary tumour before the epiphyseal plates have sealed
What is the cause of acromegaly?
Excess growth hormone due to a pituitary hormone after the epiphyseal plates have sealed
What is the cause of dwarfism?
Deficiency in GHRH or a defect in Gh secreting cells
