title: Vitamin D insufficiency is prevalent and vitamin D is inversely associated with parathyroid hormone and calcitriol in pregnant adolescents.
abstract: Few large studies have assessed changes in calcitropic hormones and maternal 25-hydroxyvitamin D (25(OH)D) status across pregnancy, and how this may impact maternal bone turnover and neonatal hormone status. We aimed to identify determinants of 25(OH)D, parathyroid hormone (PTH), and calcitriol across pregnancy in a longitudinal study of 168 pregnant adolescents (≤18 years of age). Maternal 25(OH)D, PTH, and calcitriol were assessed at mid-gestation (∼26 weeks), delivery, and in cord blood. Data were related to measures of maternal anthropometrics, dietary intake, physical activity, and bone turnover markers. Approximately 50% of teens and their infants had serum 25(OH)D ≤ 20 ng/mL; 25(OH)D was lower in African Americans versus whites (p < 0.001). PTH increased across gestation (p < 0.001). Elevated PTH (≥60 pg/mL) was detected in 25% of adolescents at delivery, and was associated with increased concentrations of serum N-telopeptide (NTX) (p = 0.028). PTH and calcitriol did not significantly differ across the range of Ca intake consumed (257-3220 mg/d). In the group as a whole, PTH was inversely associated with 25(OH)D in maternal circulation at mid-gestation (p = 0.023) and at delivery (p = 0.019). However, when the cohort was partitioned by 25(OH)D status, this relationship was only present in those with 25(OH)D ≤ 20 ng/mL, suggestive of a threshold below which 25(OH)D impacts PTH during pregnancy. Mid-gestation 25(OH)D was inversely associated with calcitriol at delivery (p = 0.023), irrespective of Ca intake. Neonatal PTH and calcitriol were significantly lower than (p < 0.001), but unrelated to maternal concentrations. These findings indicate that maternal 25(OH)D status plays a role in calcitropic hormone regulation in pregnant adolescents.
authors.affiliation: Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Bridget E
authors.initials: BE
authors.lastname: Young
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: McNanley
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Cooper
authors.forename: Allison W
authors.initials: AW
authors.lastname: McIntyre
authors.forename: Frank
authors.initials: F
authors.lastname: Witter
authors.forename: Z Leah
authors.initials: ZL
authors.lastname: Harris
authors.forename: Kimberly O
authors.initials: KO
authors.lastname: O'Brien
mesh_terms: D000293:Adolescent; D015415:Biomarkers / Q000097:blood; D016723:Bone Remodeling; D002117:Calcitriol / Q000097:blood*; D004032:Diet; D019587:Dietary Supplements; D005260:Female; D006728:Hormones / Q000097:blood; D006801:Humans; D007231:Infant, Newborn; D008137:Longitudinal Studies; D010281:Parathyroid Hormone / Q000097:blood*; D011247:Pregnancy; D015995:Prevalence; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood; D014808:Vitamin D Deficiency / Q000453:epidemiology*
chemical_list: D015415:Biomarkers; D006728:Hormones; D010281:Parathyroid Hormone; D014807:Vitamin D; C097949:1,25-dihydroxyvitamin D; C104450:25-hydroxyvitamin D; D002117:Calcitriol