TY - JOUR
T1 - Serum free 1,25‐dihydroxyvitamin d and the free 1,25‐dihydroxyvitamin d index during a longitudinal study of human pregnancy and lactation
AU - WILSON, SCOTT G.
AU - RETALLACK, ROBERT W.
AU - KENT, JACQUELINE C.
AU - WORTH, GRAEME K.
AU - GUTTERIDGE, DONALD H.
PY - 1990/1/1
Y1 - 1990/1/1
N2 -
The changes in three different indices of 1,25‐dihydroxyvitamin D (1,25(OH)
2
D) biological activity were studied longitudinally in 35 women during late pregnancy and lactation and in 26 control women. Measurements were made of maternal serum total 1,25(OH)
2
D and free 1,25(OH)
2
D concentration (by centrifugal ultrafiltration) and the free 1,25(OH)
2
D index (the molar ratio of total 1,25(OH)
2
D and vitamin D binding protein (DBP)). During late pregnancy total 1,25(OH)
2
D concentrations were significantly elevated when compared to controls, as were free 1,25(OH)
2
D and DBP concentrations and the free 1,25(OH)
2
D index. Serum total 1,25(OH)
2
D, free 1,25(OH)
2
D and DBP concentrations all fell dramatically during the first 2 weeks of lactation with total 1,25(OH)
2
D and free 1,25(OH)
2
D concentrations falling to levels below those of controls. During the course of lactation both total I,25(OH)
2
D and free 1,25(OH)
2
D levels rose significantly although they were not different from controls at 18 weeks of lactation. In contrast, the free 1,25(OH)
2
D index fell during the first 2 weeks of lactation, but remained at this level, significantly lower than controls. Neither urinary calcium excretion nor dietary calcium intake correlated with total or free 1,25(OH)
2
D, DBP, or the free 1,25(OH)
2
D index. The disagreement in the results of free 1,25(OH)
2
D concentration and free 1,25(OH)
2
D index demonstrates that these two approaches to measuring biologically active 1,25(OH)
2
D are not equivalent. In attempting to account for the increased calcium requirements of human reproduction we conclude that in pregnancy any of the 1,25(OH)
2
D measurements may be appropriate. In lactation, however, either 1,25(OH)
2
D is not a major factor or 1,25(OH)
2
D biological activity is inadequately represented by any of the currently available methods.
AB -
The changes in three different indices of 1,25‐dihydroxyvitamin D (1,25(OH)
2
D) biological activity were studied longitudinally in 35 women during late pregnancy and lactation and in 26 control women. Measurements were made of maternal serum total 1,25(OH)
2
D and free 1,25(OH)
2
D concentration (by centrifugal ultrafiltration) and the free 1,25(OH)
2
D index (the molar ratio of total 1,25(OH)
2
D and vitamin D binding protein (DBP)). During late pregnancy total 1,25(OH)
2
D concentrations were significantly elevated when compared to controls, as were free 1,25(OH)
2
D and DBP concentrations and the free 1,25(OH)
2
D index. Serum total 1,25(OH)
2
D, free 1,25(OH)
2
D and DBP concentrations all fell dramatically during the first 2 weeks of lactation with total 1,25(OH)
2
D and free 1,25(OH)
2
D concentrations falling to levels below those of controls. During the course of lactation both total I,25(OH)
2
D and free 1,25(OH)
2
D levels rose significantly although they were not different from controls at 18 weeks of lactation. In contrast, the free 1,25(OH)
2
D index fell during the first 2 weeks of lactation, but remained at this level, significantly lower than controls. Neither urinary calcium excretion nor dietary calcium intake correlated with total or free 1,25(OH)
2
D, DBP, or the free 1,25(OH)
2
D index. The disagreement in the results of free 1,25(OH)
2
D concentration and free 1,25(OH)
2
D index demonstrates that these two approaches to measuring biologically active 1,25(OH)
2
D are not equivalent. In attempting to account for the increased calcium requirements of human reproduction we conclude that in pregnancy any of the 1,25(OH)
2
D measurements may be appropriate. In lactation, however, either 1,25(OH)
2
D is not a major factor or 1,25(OH)
2
D biological activity is inadequately represented by any of the currently available methods.
UR - http://www.scopus.com/inward/record.url?scp=0025346964&partnerID=8YFLogxK
U2 - 10.1111/j.1365-2265.1990.tb00905.x
DO - 10.1111/j.1365-2265.1990.tb00905.x
M3 - Article
C2 - 2364565
AN - SCOPUS:0025346964
SN - 0300-0664
VL - 32
SP - 613
EP - 622
JO - Clinical Endocrinology
JF - Clinical Endocrinology
IS - 5
ER -