Effect of prolactin and estrogen on the serum level of 1,25-dihydroxy vitamin D and FGF23 in female rats.

INTRODUCTION: Estrogen and prolactin affect vitamin D metabolism. In conditions such as pregnancy and lactation, their interaction in regulating vitamin D metabolism and circulating FGF23 is not clearly defined. The aim of this study is to investigate this interaction in female rats. METHOD: This study was performed on 50 female adult rats, which were divided into five groups of Sham, ovariectomized rats (O), and three groups of ovariectomized rats were indicated with prolactin alone (OP), estradiol alone (OE), and a combination of estradiol and prolactin (OEP). Serum levels of 25(OH)D, 1,25(OH)2D3, FGF23, PTH, vitamin D-binding protein, calcium, and phosphorous were evaluated. RESULTS: Serum 1,25(OH)2D3 and PTH in OE were higher than the O group (P < 0.001 and P = 0.003, respectively). Serum FGF23 in the OE group was lower than the O group (P = 0.016). Serum 1,25(OH)2D3 increased in OP compared to the O group (P < 0.001) and OE group (P < 0.001). Serum FGF23 in OP was lower than the O group (P = 0.04). Furthermore, combining estradiol and prolactin showed no extra effect on increasing serum 1,25(OH)2D3. Serum 1,25(OH)2D3 was positively correlated with serum prolactin levels (r = 0.318, P = 0.017) in all five groups. CONCLUSION: It is suggested that estradiol could increase 1,25(OH)2D3 by elevating PTH and decreasing serum FGF23; however, prolactin was able to increase 1,25(OH)2D3 by lowering serum FGF23. Moreover, prolactin was shown to be more potent in augmenting serum 1,25(OH)2D3 than estrogen itself, which is important in maternal and fetal calcium supply during late pregnancy and lactation.