IGFBP-3 (IGF-binding protein)

Assessment of IGFBP-3 levels is a laboratory test used in the diagnosis of growth hormone-related disorders.

Insulin-like Growth Factor Binding Protein-3 (IGFBP-3) is the main carrier protein for insulin-like growth factors 1 and 2 (IGF-1 and IGF-2) in human serum.

IGFBP-3 is a peptide involved in the regulation of cell growth. More than 95% of IGF-1 in the blood circulates in a bound form with carrier proteins, which are classified into six groups. The most important of these is IGFBP-3. This protein has an equal binding affinity for both IGF-1 and IGF-2.

The synthesis of IGFBP-3 is primarily regulated by growth hormone. In cases of growth hormone deficiency, IGFBP-3 levels are low. IGFBP-3 levels are also reduced in conditions such as growth hormone receptor deficiency (Laron syndrome), liver diseases, the presence of anti-growth hormone antibodies, and starvation-even when growth hormone levels are elevated.

Biological variability of IGFBP-3

Unlike growth hormone, IGFBP-3 remains stable in the blood because growth hormone is secreted in an episodic manner throughout the day, resulting in highly variable levels. Therefore, pharmacological stimulation tests are not required for measuring IGFBP-3 levels.

The concentration of IGFBP-3 is less dependent on age compared to IGF-1. Levels of this protein increase in children and adolescents, reaching their peak typically between the ages of 14 and 16. After reaching adulthood, its levels gradually decline. In addition to age, IGFBP-3 levels are also influenced by pubertal development, nutrition, as well as liver and kidney function.