Fig. 2.

FGF23’s suppressive effect on PTH secretion is abolished at low plasma Ca²⁺ levels. a Plasma Ca²⁺ was rapidly decreased by an EGTA infusion (p < 0.001). After 30 min, rFGF23 was administered intravenously. b The acute lowering of plasma Ca²⁺ resulted in a dramatic increase in PTH and a higher plateau of maximal secretion (p < 0.05). In hypocalcemia, the rFGF23 had no suppressive effect on the high PTH levels. Data are expressed as mean ± SEM, n = 6 in each group