'Male and female humans are born with the same number of cardiomyocytes — the predominant cardiac cell type by mass; however, in adulthood, males have a significantly smaller proportion of cardiomyocytes. This is thought to be due to testosterone-induced apoptosis in the male heart, although differences in cardiomyocyte-regenerative capacity may also contribute.'
https://www.jci.org/articles/view/180074