IGF Binding Protein-3 (IGFBP-3)

IGFBP-3 is a protein in your blood that carries and regulates the activity of growth factors, particularly IGF-1. It is closely linked to growth hormone and helps doctors assess whether your body is producing too much or too little growth hormone. High levels may suggest the body is making excess growth hormone, while low levels can indicate growth hormone deficiency, poor nutrition, or liver problems. Because levels change naturally with age and sex, your doctor will compare your result to ranges appropriate for your age and gender. This test is typically used alongside other tests to get a complete picture of your growth hormone system.

When elevated: Elevated IGFBP-3 levels may indicate growth hormone excess (acromegaly or gigantism), and in children may reflect accelerated growth or precocious puberty. High levels have also been associated with increased risk of certain hormone-sensitive cancers in epidemiological studies, though causality has not been established. Elevated IGFBP-3 in the context of normal or high IGF-1 supports evaluation for GH hypersecretion. When low: Low IGFBP-3 levels are associated with growth hormone deficiency, which may present as growth failure in children or metabolic abnormalities in adults. Reduced levels are also seen in states of protein malnutrition, hepatic insufficiency, and hypothyroidism, reflecting impaired hepatic synthetic capacity. Low IGFBP-3 in conjunction with low IGF-1 strengthens the clinical suspicion for GH deficiency or secondary causes of GH axis suppression.

IGFBP-3 reflects growth hormone status and IGF availability—both central to muscle protein synthesis, recovery, and adaptation to training. Athletes may find this useful as part of a broader GH/IGF axis assessment, particularly when investigating recovery quality, training tolerance, or age-related changes in anabolic capacity; however, it is a supporting marker rather than a primary performance indicator.