Combining with an extracellular or intracellular messenger to initiate a change in cell activity [goid 4872] [evidence IEA]; A receptor that binds an extracellular ligand and transmits the signal to a heterotrimeric G-protein complex. These receptors are characteristically seven-transmembrane receptors and are made up of hetero- or homodimers [goid 4930] [evidence IEA]; Combining with calcitonin to initiate a change in cell activity [goid 4948] [pmid 7588285] [evidence IDA]; Combining with calcitonin to initiate a change in cell activity [goid 4948] [evidence IEA]; Interacting selectively with calcitonin, a peptide hormone responsible for reducing serum calcium levels by inhibiting osteoclastic bone reabsorption and promoting renal calcium excretion. It is synthesized and released by the C cells of the thyroid [goid 32841] [pmid 7588285] [evidence IPI]; Interacting selectively with calcitonin, a peptide hormone responsible for reducing serum calcium levels by inhibiting osteoclastic bone reabsorption and promoting renal calcium excretion. It is synthesized and released by the C cells of the thyroid [goid 32841] [pmid 8078488] [evidence IPI]; Interacting selectively with calcitonin, a peptide hormone responsible for reducing serum calcium levels by inhibiting osteoclastic bone reabsorption and promoting renal calcium excretion. It is synthesized and released by the C cells of the thyroid [goid 32841] [pmid 7769107] [evidence IDA]; Interacting selectively with calcitonin, a peptide hormone responsible for reducing serum calcium levels by inhibiting osteoclastic bone reabsorption and promoting renal calcium excretion. It is synthesized and released by the C cells of the thyroid [goid 32841] [pmid 7588285] [evidence IPI]; Interacting selectively with calcitonin, a peptide hormone responsible for reducing serum calcium levels by inhibiting osteoclastic bone reabsorption and promoting renal calcium excretion. It is synthesized and released by the C cells of the thyroid [goid 32841] [pmid 7769107] [evidence IDA]; Interacting selectively with calcitonin, a peptide hormone responsible for reducing serum calcium levels by inhibiting osteoclastic bone reabsorption and promoting renal calcium excretion. It is synthesized and released by the C cells of the thyroid [goid 32841] [pmid 8078488] [evidence IDA]; Interacting selectively with calcitonin, a peptide hormone responsible for reducing serum calcium levels by inhibiting osteoclastic bone reabsorption and promoting renal calcium excretion. It is synthesized and released by the C cells of the thyroid [goid 32841] [pmid 15563840] [evidence IPI]