In pregnancy and with aging, STAT3 in cardiac myocytes has been shown to be a critical determinant of endothelial function and health, although by different mechanisms: induction of protective anti-oxidant genes is important in pregnancy, whereas loss of STAT3-mediated repression of miR-199a expression may contribute to endothelial dysfunction in the heart with aging. Here, STAT3 is linked to endothelial dysfunction.