Therefore, in order to assess the undisturbed impact of GLP-1 analogues on patients’ blood glucose levels, it was decided to make measurements in the group of patients with medullary thyroid carcinoma (MTC), also diagnosed by [Lys40(Ahx-HYNIC-99mTc/EDDA)NH2]-exendin-4. This evidence concerns the gene GCG and medullary thyroid gland carcinoma.