This receptor binds insulin-like growth factor 1 (IGF1) with a high affinity and IGF2 with a lower affinity. It has a tyrosine-protein kinase activity, which is necessary for the activation of the IGF1-stimulated downstream signaling cascade. When present in a hybrid receptor with INSR, binds IGF1. PubMed:12138094 shows that hybrid receptors composed of IGF1R and INSR isoform Long are activated with a high affinity by IGF1, with low affinity by IGF2 and not significantly activated by insulin, and that hybrid receptors composed of IGF1R and INSR isoform Short are activated by IGF1, IGF2 and insulin. In contrast, PubMed:16831875 shows that hybrid receptors composed of IGF1R and INSR isoform Long and hybrid receptors composed of IGF1R and INSR isoform Short have similar binding characteristics, both bind IGF1 and have a low affinity for insulin.

Found as a hybrid receptor with INSR in muscle, heart, kidney, adipose tissue, skeletal muscle, hepatoma, fibroblasts, spleen and placenta (at protein level). Expressed in a variety of tissues.

Defects in IGF1R are a cause of insulin-like growth factor 1 resistance (IGF1RES) [MIM:270450]. It is a disorder characterized by intrauterine growth retardation and poor postnatal growth accompanied with increased plasma IGF1.

Belongs to the protein kinase superfamily. Tyr protein kinase family. Insulin receptor subfamily.
Contains 3 fibronectin type-III domains.
Contains 1 protein kinase domain.

The cytoplasmic domain of the beta subunit is autophosphorylated on tyrosine residues in response to insulin-like growth factor I (IGF I).
Phosphorylation of Tyr-980 is required for IRS1- and SHC1-binding.

Membrane.