The calcitonin receptor (CT) is a G protein-coupled receptor that binds the peptide hormone calcitonin and is involved in maintenance of calcium homeostasis, particularly with respect to bone formation and metabolism. The function of the CT receptor protein is modified through its interaction with Receptor activity-modifying proteins (RAMPs), forming the multimeric amylin receptors AMY1 (CT + RAMP1), AMY2 (CT + RAMP2), and AMY3 (CT+ RAMP3).