Research into hormone secretion by the heart and the release of such hormones in detectable amounts in response to given clinical conditions has provided new perspectives full of hopes but also uncertainties. These hormones, called natriuretic peptides, have diuretic, natriuretic and vasodilating properties. In heart failure, a relationship between ventricular dysfunction and the levels of these peptides, with implications for morbidity and mortality, has been demonstrated. Less research has been carried out into heart transplant, and while increased levels of hormones are also observed when graft dysfunction occurs, their role in acute rejection or as an independent factor associated with prognosis has not been clarified.