Iain Macintyre FRS was a British endocrinologist who made important contributions to the understanding of calcium regulation and bone metabolism. Shortly after the hormone calcitonin had been described by Harold Copp, Macintyre's team was the first to isolate and sequence the hormone and to demonstrate its origin in the parafollicular cells of the thyroid gland. He subsequently analysed its physiological actions. Along with H. R. Morris he isolated and sequenced calcitonin gene-related peptide. Later research centred on the role played by nitric oxide on bone metabolism.