The relationship between parathyroid hormone and 25-hydroxyvitamin D during and after pregnancy

Abstract

Context: There is debate about whether women may need greater vitamin D supplementation when pregnant. However, it is unclear whether the 25-hydroxyvitamin D (25-OH-D) concentration required for suppression of PTH (ie, suggesting vitamin D sufficiency) differs between pregnancy and the nongravid state. Objective: To systematically characterize the relationship between 25-OH-D and PTH during and after pregnancy. Design/Setting/Participants: In this study, 468 women underwent serial assessment of serum 25-OH-D and PTH in late pregnancy, at 3 months postpartum, and at 12 months postpartum. At each visit, segmented regression analysis was performed to: 1) determine the best model to fit the relationship between 25-OH-D and PTH; and 2) identify the 25-OH-D threshold above which PTH is maximally suppressed. Results: Serum 25-OH-D and PTH were inversely correlated at each of the pregnancy (r = -0.33; P < .0001), 3 months postpartum (r = -0.37; P < .0001), and 12 months postpartum (r = -0.34; P