Insulin-like Growth Factor-Binding Protein-3 (IGFBP-3)(h) RIA

Radioimmunoassay (RIA) for the determination of human IGFBP-3 in serum, plasma, or other human biological fluids (e.g. follicular fluid, seminal plasma).<br><br>

Insulin-like growth factors (IGF)-I and -II are bound to specific binding proteins (IGFBPs) in the circulation. Until now at least seven binding proteins have been identified and classified as IGFBP-1 to -7 (1, 2).<br><br>

Insulin-like growth factors (IGF)-I and -II are bound to specific binding proteins (IGFBPs) in the circulation. Until now at least seven binding proteins have been identified and classified as IGFBP-1 to -7 (1, 2). These binding proteins are expressed by different kinds of tissues and show specific posttranslational modifications like glycosylation or phosphorylation. Their main function is – together with specific proteases - the regulation of the IGF bioavailability. The most frequent IGFBP in blood is IGFBP-3. Most IGFBP-3 in the circulation is bound in a ternary complex formed by IGF-I or -II, IGFBP-3 and the so called acid-labile subunit (ALS, 3-5). Most of the IGFBP-3 in blood is present as the high molecular weight ternary complex, however, small amounts of free IGFBP-3 are also found (6, 7).<br><br>

The development of specific radioimmunoassays for IGFBP-3, able to detect IGFBP-3 within the ternary complex, provided new in-sights into its regulation (6-9). Several factors besides GH influence IGFBP-3 levels: age including sexual development, nutrition, hypothyroidism, diabetes mellitus, liver function and kidney function. Measurement over 24 hours revealed constant circadian levels (12,13). For research use only, not for use in diagnostic procedures.