Insulin-like Growth Factor 1
Insulin-like growth factor 1 (IGF-1) is a hormone made mainly by the liver in response to growth hormone. It carries out many of growth hormone's effects on the body.
Strongly age-dependent; peaks in adolescence. Preferred over GH for GH deficiency/excess screening due to stable levels. Nutrition state affects values.
Because IGF-1 levels stay relatively steady through the day, it gives a more stable picture of growth hormone activity than growth hormone itself, which fluctuates in bursts. It supports growth in childhood and helps maintain muscle, bone, and tissue repair in adults. Levels naturally change with age, being highest in adolescence and declining over adulthood.
A high IGF-1 may reflect excess growth hormone activity, which in adults can be associated with a condition called acromegaly. It can also be influenced by age and other factors, so a single elevated result usually prompts further testing rather than a diagnosis.
A low IGF-1 can suggest reduced growth hormone activity, but it may also reflect poor nutrition, liver conditions, or other illness, so context matters.
IGF-1 is interpreted against age- and sometimes sex-specific reference ranges rather than one universal number. Compare your value to the age-adjusted range on your report and review it with your clinician.
Sources
Educational context only, not medical advice or a diagnosis. Reference ranges vary by lab, age and sex; always discuss your results with a clinician.