regulation of heart rate by chemical signal regulation of heart rate by hormone regulation of the rate of heart contraction by hormone The process in which the hormones modulates the rate of heart muscle contraction. A hormone is one of a group of substances formed in very small amounts in one specialized organ or group of cells and carried (sometimes in the bloodstream) to another organ or group of cells, in the same organism, upon which they have a specific regulatory action. biological_process GO:0003064 hormonal cardiac chronotropy