title: The Relationship Between Parathyroid Hormone and 25-Hydroxyvitamin D During and After Pregnancy.
abstract: 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.
  
  
  
  To systematically characterize the relationship between 25-OH-D and PTH during and after pregnancy.
  
  
  
  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.
  
  
  
  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 < .0001) assessments. In pregnancy, PTH first rises when 25-OH-D falls below 82 nmol/L (95% confidence interval, 61–103) and follows a linear relationship with declining 25-OH-D thereafter. In contrast, at both postpartum visits, there was a curvilinear relationship between 25-OH-D and PTH below the 25-OH-D threshold at which PTH is suppressed (71 nmol/L [61–81] at 3 months and 81 nmol/L [61–100] at 12 months). The 25-OH-D thresholds for PTH suppression in pregnancy and at 3 and 12 months postpartum were not significantly different from one another (all pairwise P ≥ .26).
  
  
  
  Although the shape of the relationship between 25-OH-D and PTH differs between pregnancy and the postpartum, the 25-OH-D thresholds for PTH suppression are similar, supporting comparable targets for vitamin D supplementation.
authors.affiliation: Leadership Sinai Centre for Diabetes (C.K.K., C.Y., A.J.H., B.Z., R.R.), Mount Sinai Hospital, Toronto, ON M5T 3L9, Canada; Division of Endocrinology (C.K.K., A.J.H., P.W.C., B.Z., R.R.), and Department of Nutritional Sciences (A.J.H.), University of Toronto, Toronto, ON M5S 1A1, Canada; Keenan Research Centre for Biomedical Science of St Michael's Hospital (P.W.C.), Toronto, ON M5B 1W8, Canada; Department of Laboratory Medicine and Pathobiology (P.W.C.), and Division of Obstetrics and Gynecology (M.S.), University of Toronto, Toronto, ON M5S 1A1, Canada; and Lunenfeld-Tanenbaum Research Institute (B.Z., R.R.), Mount Sinai Hospital, Toronto, ON M5T 3L9, Canada.
authors.forename: Caroline K
authors.initials: CK
authors.lastname: Kramer
authors.affiliation: Leadership Sinai Centre for Diabetes (C.K.K., C.Y., A.J.H., B.Z., R.R.), Mount Sinai Hospital, Toronto, ON M5T 3L9, Canada; Division of Endocrinology (C.K.K., A.J.H., P.W.C., B.Z., R.R.), and Department of Nutritional Sciences (A.J.H.), University of Toronto, Toronto, ON M5S 1A1, Canada; Keenan Research Centre for Biomedical Science of St Michael's Hospital (P.W.C.), Toronto, ON M5B 1W8, Canada; Department of Laboratory Medicine and Pathobiology (P.W.C.), and Division of Obstetrics and Gynecology (M.S.), University of Toronto, Toronto, ON M5S 1A1, Canada; and Lunenfeld-Tanenbaum Research Institute (B.Z., R.R.), Mount Sinai Hospital, Toronto, ON M5T 3L9, Canada.
authors.forename: Chang
authors.initials: C
authors.lastname: Ye
authors.affiliation: Leadership Sinai Centre for Diabetes (C.K.K., C.Y., A.J.H., B.Z., R.R.), Mount Sinai Hospital, Toronto, ON M5T 3L9, Canada; Division of Endocrinology (C.K.K., A.J.H., P.W.C., B.Z., R.R.), and Department of Nutritional Sciences (A.J.H.), University of Toronto, Toronto, ON M5S 1A1, Canada; Keenan Research Centre for Biomedical Science of St Michael's Hospital (P.W.C.), Toronto, ON M5B 1W8, Canada; Department of Laboratory Medicine and Pathobiology (P.W.C.), and Division of Obstetrics and Gynecology (M.S.), University of Toronto, Toronto, ON M5S 1A1, Canada; and Lunenfeld-Tanenbaum Research Institute (B.Z., R.R.), Mount Sinai Hospital, Toronto, ON M5T 3L9, Canada.
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Hanley
authors.affiliation: Leadership Sinai Centre for Diabetes (C.K.K., C.Y., A.J.H., B.Z., R.R.), Mount Sinai Hospital, Toronto, ON M5T 3L9, Canada; Division of Endocrinology (C.K.K., A.J.H., P.W.C., B.Z., R.R.), and Department of Nutritional Sciences (A.J.H.), University of Toronto, Toronto, ON M5S 1A1, Canada; Keenan Research Centre for Biomedical Science of St Michael's Hospital (P.W.C.), Toronto, ON M5B 1W8, Canada; Department of Laboratory Medicine and Pathobiology (P.W.C.), and Division of Obstetrics and Gynecology (M.S.), University of Toronto, Toronto, ON M5S 1A1, Canada; and Lunenfeld-Tanenbaum Research Institute (B.Z., R.R.), Mount Sinai Hospital, Toronto, ON M5T 3L9, Canada.
authors.forename: Philip W
authors.initials: PW
authors.lastname: Connelly
authors.affiliation: Leadership Sinai Centre for Diabetes (C.K.K., C.Y., A.J.H., B.Z., R.R.), Mount Sinai Hospital, Toronto, ON M5T 3L9, Canada; Division of Endocrinology (C.K.K., A.J.H., P.W.C., B.Z., R.R.), and Department of Nutritional Sciences (A.J.H.), University of Toronto, Toronto, ON M5S 1A1, Canada; Keenan Research Centre for Biomedical Science of St Michael's Hospital (P.W.C.), Toronto, ON M5B 1W8, Canada; Department of Laboratory Medicine and Pathobiology (P.W.C.), and Division of Obstetrics and Gynecology (M.S.), University of Toronto, Toronto, ON M5S 1A1, Canada; and Lunenfeld-Tanenbaum Research Institute (B.Z., R.R.), Mount Sinai Hospital, Toronto, ON M5T 3L9, Canada.
authors.forename: Mathew
authors.initials: M
authors.lastname: Sermer
authors.affiliation: Leadership Sinai Centre for Diabetes (C.K.K., C.Y., A.J.H., B.Z., R.R.), Mount Sinai Hospital, Toronto, ON M5T 3L9, Canada; Division of Endocrinology (C.K.K., A.J.H., P.W.C., B.Z., R.R.), and Department of Nutritional Sciences (A.J.H.), University of Toronto, Toronto, ON M5S 1A1, Canada; Keenan Research Centre for Biomedical Science of St Michael's Hospital (P.W.C.), Toronto, ON M5B 1W8, Canada; Department of Laboratory Medicine and Pathobiology (P.W.C.), and Division of Obstetrics and Gynecology (M.S.), University of Toronto, Toronto, ON M5S 1A1, Canada; and Lunenfeld-Tanenbaum Research Institute (B.Z., R.R.), Mount Sinai Hospital, Toronto, ON M5T 3L9, Canada.
authors.forename: Bernard
authors.initials: B
authors.lastname: Zinman
authors.affiliation: Leadership Sinai Centre for Diabetes (C.K.K., C.Y., A.J.H., B.Z., R.R.), Mount Sinai Hospital, Toronto, ON M5T 3L9, Canada; Division of Endocrinology (C.K.K., A.J.H., P.W.C., B.Z., R.R.), and Department of Nutritional Sciences (A.J.H.), University of Toronto, Toronto, ON M5S 1A1, Canada; Keenan Research Centre for Biomedical Science of St Michael's Hospital (P.W.C.), Toronto, ON M5B 1W8, Canada; Department of Laboratory Medicine and Pathobiology (P.W.C.), and Division of Obstetrics and Gynecology (M.S.), University of Toronto, Toronto, ON M5S 1A1, Canada; and Lunenfeld-Tanenbaum Research Institute (B.Z., R.R.), Mount Sinai Hospital, Toronto, ON M5T 3L9, Canada.
authors.forename: Ravi
authors.initials: R
authors.lastname: Retnakaran
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008962:Models, Theoretical; D010281:Parathyroid Hormone / Q000097:blood*; D049590:Postpartum Period / Q000097:blood*; D011247:Pregnancy; D011446:Prospective Studies; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D010281:Parathyroid Hormone; D014807:Vitamin D; C104450:25-hydroxyvitamin D