NPPA and hypothyroidism: Furthermore, the study of Hajje et al. showed that hypothyroidism induced by propylthiouracil induced the expression of the fetal genes for atrial natriuretic peptide (ANP; hormone secreted in response to myocyte stretch in the cardiac atria, similar to BNP in its hemodynamic effects, with vasodilating properties) and BNP; this response was abolished by LT4 treatment (66).