|
| Origin | Gene regulation | Serum levels | Affinity for insulin/IGF family members | Function |
|
| Insulin | Beta cells of the pancreas | Glucose uptake, protein synthesis | 11–14 U/mL | IR >IGF-IR> IGF-IIR | –Regulates carbohydrate, fat, and protein metabolism. |
| –Mitogenic effect. |
|
| IGF-I | Liver, bone, and several other tissues. | Hormones, growth factors, cytokines, nutrition, smoking, exercise. | 100–200 ng/mL | IGF-IR> IGF-IIR > IR | –Regulates embryonic growth and specific differentiation in adult tissues. |
| –Involved in cell proliferation, transformation, and antiapoptotic activity. |
|
| IGF-II | Liver, kidney, bone, and several other tissues. | Tumor suppressor proteins WT1 and p53, HIF-1, genomic imprinting. | 400–700 ng/mL | IGF-IIR> IGF-IR>IR | –Functional during embryonic and fetal growth. |
|
| IGFBPs | IGFBP-1: liver, decidua. | BP-1: insulin, steroids. | BP-1, BP-2: vary during the day and meals. | BP-1, BP-3, BP-5: IGF-I> IGF-II | –Regulate transport and half-life of IGFs between different body compartments. |
| IGFBP-2: CNS. | BP-2: insulin, metabolic process. |
| IGFBP-3: several tissues. | BP-3: GH, PTH, cytokines, p53, estradiol, steroids. |
| IGFBP-4: bone, CNS, prostate. | BP-4: vitamin D, parathyroid hormone. | BP-3: vary in relation to age and sex 1500–5580 ng/mL. | BP-2, BP-6: IGF-II>IGF-I | –Regulate IGF independent effect on cell proliferation and apoptosis. |
| IGFBP-5: kidney, bone, mammary gland. | BP-5: GH, prolactin, vitamin D. |
| IGFBP-6: ovary, prostate. | BP-6: GH, FSH. |
|
