/ Dictionary / Index C calcitonin: Meaning and Definition of Find definitions for: cal•ci•to•nin Pronunciation: (kal"si-tō'nin), [key] — n. Biochem. a polypeptide hormone that participates in the regulation of calcium levels in vertebrates by inhibiting loss of calcium from bone to the blood. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: calcitonin (Thesaurus) calcite calcitriol Related Content Daily Word Quiz: lunar Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language