The hormones of the Heart, Kidney and Gastrointestinal Tract are: 

(i) Heart/Atrium : Atrial wall of human heart produces important peptide hormone called atrial natriuretic factor (ANF). ANF reduces blood pressure. When the blood pressure is enhanced, some special c ells secrete ANF, that produces vasodilatory actions on the blood pressure. The blood vessels are dilated and blood pressure declines as a result. 

(ii) Kidney : Juxtaglomerular cells of kidney secrete a peptide hormone called erythropoietin. It stimulates erythropoiesis or formation of RBCs of blood. 

(iii) GI Tract : The endocrine cells found in various parts of gastro-intestinal tract (GI tract) secrete four peptide hormones gastrin, secretin, cholecystokinin (CCK) as well as gastric inhibitory peptide or GIP. 

(a) Gastrin : It acts on gastric glands. It stimulates secretion of hydrochloric acid (HCI) and pepsinogen. 

(b) Secretin : It acts on the exocrine pancreas. It stimulates secretion of water and bicarbonate ions. 

(c) CCK : It acts on both pancreas and gall bladder. It stimulates the secretion of pancreatic enzymes and bile juice respectively. 

(d) GIP: It suppresses gastric secretion and motility.