Insulin-Like Growth Factor-1 (IGF-1) with Z-Score

IGF-1 is a hormone made mainly in the liver that helps control growth and body composition throughout your life. It is largely regulated by growth hormone from the pituitary gland in the brain. Because normal IGF-1 levels change significantly with age and differ between males and females, your result is reported as a Z-score, which shows how your level compares to other healthy people of the same age and sex. A Z-score that is too high may suggest the body is producing too much growth hormone, while a Z-score that is too low may suggest a deficiency or that another condition such as poor nutrition or liver problems is affecting the result. Your doctor will consider this result alongside your symptoms, other tests, and your overall health before drawing any conclusions.

When elevated: Elevated IGF-1 Z-scores raise concern for GH excess states, most notably acromegaly in adults or gigantism in children, and warrant further evaluation with GH suppression testing. Persistently high levels are associated with increased risks of certain malignancies, cardiovascular complications, and metabolic disturbances. High IGF-1 may also reflect exogenous GH administration or, rarely, ectopic GH or IGF-1 secretion. When low: Low IGF-1 Z-scores may indicate GH deficiency (congenital or acquired), hypopituitarism, or GH insensitivity (Laron syndrome). Secondary causes such as malnutrition, liver disease, hypothyroidism, poorly controlled diabetes mellitus, and chronic illness can suppress IGF-1 independent of GH status. In adults, low IGF-1 is associated with reduced bone mineral density, adverse body composition, impaired quality of life, and potentially increased cardiovascular risk.

IGF-1 is a key anabolic hormone that supports muscle protein synthesis, recovery, and adaptation to training stress. Athletes often monitor IGF-1 to assess training responsiveness and recovery status, as chronic overtraining or inadequate nutrition can suppress levels; the Z-score helps you compare your result to age and sex-matched peers rather than generic ranges.