In 2006, 3-aminoethyl estradiol (EDL) was conjugated to glutamate peptide (GAP) to yield GAP-EDL (a functional estrogen ligand) and then labeled with 99mTc to develop a radioactive imaging probe 99mTc-GAP-EDL, which was first reported to target endometriotic lesions in a rabbit model of endometriosis [38]. This evidence concerns the gene LIPG and endometriosis.