FGF23 has also been reported to decrease PTH production, thereby further ensuring that Ca homeostasis is restored [43, 44].
When the ECF Ca is raised into the hypercalcemic range, the opposite sequence of events occurs, that is, PTH secretion is reduced due to the stimulation of the parathyroid CaSR, and renal 1,25(OH)2D production is decreased. In addition, the elevated Ca per se may stimulate the renal CaSR in the CTAL, thus inducing calciuria. Therefore, the effect of suppressing PTH release and 1,25(OH)2D synthesis and of stimulating renal CaSR results in reduced renal tubular Ca reabsorption, decreased skeletal Ca release, and decreased intestinal Ca absorption, resulting in the normalization of the elevated ECF Ca.
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