<qa>  What is the endocrine system ubiquitous in human tissues?iv Vitamin D improves cardiac function and morphology: The Vitamin D endocrine system is ubiquitous in human tissues, including the myocardium and the vascular endothelium. There is now mounting evidence from animal studies that Vitamin D directly affects cardiac function and structure through a genomic action on cardiac myocytes. Vitamin D knockout mice show an increase in cardiomyocyte hypertrophy, cardiac fibrosis and heart weight 8. More importantly, treatment with vitamin D in spontaneously hypertensive heart failure rats and wild type mice has been shown to attenuate cardiac hypertrophy and fibrosis, and modulates cardiac myocyte contractility, respectively 9;10. 