In this trial the investigators will determine the influence of calcimimetic therapy on left ventricular hypertrophy (LVH) in hemodialysis patients with sHPT: They will perform a head-2-head trial testing etelcalcetide vs. alfacalcidol treatment on top of conventional HPT therapy (phosphate binders, calcium supplementation and if necessary vitamin D substitution or cinacalcet) for 12 months. Etelcalcetide or alfacalcidol will be administered intravenously three times per week following chronic hemodialysis treatment. The primary end point will be a change in left ventricular mass index (LVMI) that will be assessed using cardiac magnetic resonance imaging (cMRI) at baseline and after 12 months of treatment. As secondary end points we will measure changes in left atrial diameter (LAD), cardiac fibrosis (using T1 mapping and cardiac strain), wall motion abnormalities and left ventricular function (measured in cMRI and echocardiography), changes in serum FGF 23 and soluble Klotho levels as well as changes in proBNP as well as pre- and postdialysis troponin T (TnT) levels.