Normal Growth Flashcards
(21 cards)
Where is GH released?
Anterior pituitary gland
What is another name for GH?
Somatotrophin
What is unusual about GH as a peptide hormone?
Around 50% bound to carrier proteins
What does GH require to stimulate growth?
Insulin and thyroid hormones
When does GH become important for growth?
After the first 8-10 months of life
How is the growth effect achieved by GH?
Hyperplasia and hypertrophy
How is the growth effect of GH achieved?
Through the intermediate IGF-1
On what tissue will IGF have a hypoglycaemic effect?
Muscle (liver and adipose have few IGF receptors)
Where is IGF-1 secreted from?
Liver and other cells in response to GH
How does IGF-1 exert a negative feedback effect on GH?
Stimulate somatostatin
Inhibit GHRH
What are the direct effects of GH?
Increase gluconeogenesis by the liver
Reduces the ability of insulin to stimulate glucose uptake by muscle and adipose tissue
Makes adipocytes more sensitive to lipolytic stimuli
How is release of GH controlled?
The hypothalamus through GHRH and GHIH
When is GH at its highest concentration during children’s sleep?
Deep delta sleep
What can stimulate release of GHRH? (5)
Actual or potential decrease in energy supply to cells
Increased amounts of amino acids in the plasma
Stressful stimuli
Delta sleep
Oestrogen and androgens
What stimuli can increase GHIH release? (4)
Glucose
FFA
REM sleep
Cortisol
What three factors influence growth?
Genes
Nutrition
Hormones
What hormones influence intrauterine growth?
Insulin and IGF-II
How do thyroid hormones influence growth?
Help ossification of cartilage, teeth maturation, contours of body and proportions and NS development.
Have a permissive effect on GH.
What is the usual cause of hypersecretion of GH?
Endocrine tumours
What can hypersecretion of GH lead to?
Gigantism (before epiphyseal plates close)
Acromegaly
What are some of the causes of reduced height? (6)
Deficiency in GHRH Abnormal GH secreting cells End organ unresponsive to GH Genetic mutations Precocious puberty Hypothyroidism in children
