Insulin-like Growth Factor II, IGF-II, is a major growth hormone made by Theca cells during gestation. While IGF-II is known to engage the IGF-I receptor (IGF1R) to mediate embryonic growth, IGF-II is also known to bind the IGF-II receptor (IGF2R). IGF2R is thought to be signaling dead receptor that acts as a sink by binding up free IGF-II. Recombinant IGF-II is non-glycosylated Protein, containing 67 amino acids, with a molecular weight of 7.5 kDa.