[Local data] Serum 3-epi-25-hydroxyvitamin D concentration and its influencing factors


3-epi-25-hydroxyvitamin D [3-epi-25 (OH) D3], an isomeric form of 25 (OH) D3, is also a biologically inactive metabolite which may lead to underestimation of hypovitaminosis D. A local study conducted by the Chinese University of Hong Kong reported levels of 3-epi-25 (OH) D3 in maternal and fetal circulation, as well as factors influencing their concentrations.

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In this first Chinese cohort, a total of 1502 and 1321 archived maternal and umbilical cord serum samples from previous study* were tested respectively. Key findings are listed below:

Vitamin D deficiency

  • Number of deficient mothers: 590 (39.3%) [total serum 25 (OH) D level < 50 nmol/L]
  • Number of deficient newborns: 952 (72.1%) [umbilical cord serum total 25 (OH) D level < 50 nmol/L]

Severe vitamin D deficiency

  • Number of severely deficient mothers: 25 (1.7%) [total serum 25 (OH) D level < 25 nmol/L]
  • Number of severely deficient newborns: 116 (8.8%) [umbilical cord serum total 25 (OH) D level < 25 nmol/L]

Presence of 3-epi-25 (OH) D3

  • 3-epi-25 (OH) D3 was detected in 94.5% (1419 out of 1502) maternal and 92.1% (1217 out of 1321) neonatal samples
  • The median 3-epi-25 (OH) D3 concentrations in maternal and umbilical cord sera were 1.9 nmol/L and 1.7 nmol/L respectively
  • The greatest absolute concentrations of 3-epi-25-(OH) D3 were 14.2 nmol/L and 10.9 nmol/L in maternal and neonatal samples respectively

Maternal serum 3-epi-25 (OH) D3 level was associated with

  • Pregnancy with a male fetus
  • Maternal glycemic levels
  • Maternal 25 (OH) D3 levels
  • Exposure to ambient solar radiation at the time of sample collection

Umbilical cord serum 3-epi-25 (OH) D3 level was associated with

  • Advanced maternal age
  • Multiparity
  • Insufficient maternal gestational weight gain^
  • Maternal glycemic status
  • Earlier gestational age at delivery
  • Maternal and umbilical sera 3-epi-25 (OH) D3 levels
  • Exposure to ambient solar radiation at the time of sample collection

*The Hyperglycemia and Adverse Pregnancy Outcome Study cohort from Hong Kong
^According to the Institute of Medicine recommendation


Link to the full article:


Mao D et al. Maternal and neonatal 3-epi-25-hydroxyvitamin D concentration and factors influencing- their concentrations. J Endocr Soc. 2021;6(1):bvab170.

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