PTH and chronic kidney disease: A 2016 meta-analysis of non-dialysis CKD patients treated with nutritional vitamin D (cholecalciferol or ergocalciferol) versus placebo across four randomised controlled trials demonstrated that although nutritional vitamin D increased 25(OH)D levels and lowered PTH when compared to placebo, data were based on a small population of 122 patients and there was substantial heterogeneity in effect sizes between studies; it therefore concluded that additional data were needed [45, 46].