In contrast, in a study conducted by Hostutler et al. [111] with healthy and CKD cats, no difference in serum PTH concentrations was observed after a 14-day oral treatment with calcitriol (2.5 ng/kg every 24 h or 8.75 ng/kg every 84 h), and no difference in serum ionized calcium concentrations was noticed. Here, PTH is linked to chronic kidney disease.