Hepatocyte — GH receptor and IGF-1 synthesis
Target gland or tissue · GH receptor JAK2-STAT5 IGFBP-3
GH binds its hepatic receptor and signals through JAK2 and STAT5b to transcribe IGF-1, which circulates bound to IGFBP-3 and the acid-labile subunit. That binding gives IGF-1 a long half-life and makes it the stable measure of GH output.
Traced from the start
- GHRH and somatostatin (arcuate and periventricular nuclei)
- Somatotroph — growth hormone
- Hepatocyte — GH receptor and IGF-1 synthesis
Detail
- Why IGF-1 is measured
- GH is pulsatile; IGF-1 is steady across the day and reflects integrated secretion
- Requires
- Adequate nutrition and insulin — malnutrition, poorly controlled diabetes, coeliac disease and liver failure lower IGF-1 despite high GH
- Age dependence
- IGF-1 must be read against an age-matched range: it peaks in puberty and falls with age
When it goes wrong
GH receptor mutation (Laron syndrome)
Severe short stature with high GH and low IGF-1; growth hormone is useless and recombinant IGF-1 is the treatment
Chronic liver disease or anorexia nervosa
Acquired GH resistance: high GH with low IGF-1 and poor growth in children
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