FGF23 and primary hyperparathyroidism: First, in our study no serum parathyroid hormone, vitamin D and fibroblast growth factor 23 levels are available for most of the patients which may help to delineate the underlying mechanisms for the association between serum calcium and HFpEF, so it is impossible to absolutely exclude potential confounding factors including primary hyperparathyroidism and secondary hyperparathyroidism due to vitamin D deficiency and/or renal insufficiency.