This study describes the relationship between MHT use and prognostically important cardiac phenotypes and indicates lower LV end-diastolic and LA maximal volumes in women who used MHT ≥ 3 years compared to those who never received treatment. Increases in LV volumes–LV dilatation–is associated with cardiac decompensation and poor prognosis in a range of cardiovascular diseases. Increases in end-diastolic volume and end-systolic volume have been demonstrated to be associated with an increased risk of heart failure in asymptomatic individuals  whilst reduction in LV volumes–indicative of reverse cardiac remodelling–is associated with favourable outcomes . Equivalently, LA enlargement, as determined by LA maximal volume, is a robust and independent predictor of incident cardiovascular events  whilst reduction in LA volumes (reverse remodelling) is associated with lower mortality and risk of heart failure . There was no significant difference in LV mass between MHT users ≥ 3 years and those who had never used MHT. LV mass is one of the most important cardiovascular imaging-derived phenotypes with increases in LV mass predicting a higher incidence of cardiovascular events and mortality .