Anita Subramanian, Alison D Gernand
Journal: BMC women's health 2019;19(1):19
PMID: 30691458
Vitamin D deficiency is highly prevalent in women compared to men particularly at reproductive age. The Institute of Medicine defines vitamin D deficiency as having concentrations of 25-hydroxyvitamin D [25(OH)D] < 30 nmol/l and vitamin D insufficiency as 25(OH)D < 50 nmol/l. Furthermore, 25(OH)D is further metabolised in the kidneys to 1,25 dihydroxyvitamin D [1,25(OH)2D], the biologically active form of vitamin D. The aim of this study was to conduct a systematic review of studies that assessed concentrations of 25(OH)D and/or 1,25(OH)2D longitudinally to assess if these vitamin D biomarkers change across the normal menstrual cycle. This study is a systematic review of ten longitudinal studies. Results show conflicting data between studies. For example, 1,25(OH)2D concentrations increased across the menstrual cycle in a few studies but did not change in others. 25(OH)D concentrations changed across the cycle in one study but not others. This was due to the fact that only a few studies have examined vitamin D metabolites across the menstrual cycle, thus, there is limited to insufficient data to be able to understand potential changes or lack thereof. Authors conclude that future studies are needed to better understand 25(OH)D and 1,25(OH)2D in menstruating women. These studies should particularly focus on examining both metabolites (at minimum) at least two points across the menstrual cycle using the robust lab methods.
BACKGROUND
Accurate estimation of vitamin D status is important for health research and can impact prevention and treatment of deficiency in women of reproductive age. We aimed to assess if blood concentrations of 25-hydroxyvitamin D [25(OH)D] or 1,25-dihydroxyvitamin D [1,25(OH)D] change across the menstrual cycle.
METHODS
We conducted a systematic search in PubMed, Web of Science, CAB and BIOSIS of literature published until December 2018 which reported concentrations of vitamin D metabolites at two or more identified points among women with regular menstrual cycles.
RESULTS
Ten longitudinal studies met the inclusion criteria; nine studies measured 1,25(OH)D and five studies measured 25(OH)D. Study size ranged from 5 to 47 subjects, with an age range of 18-47 years. One study found a decrease in concentration of 25(OH)D in the periovulatory and luteal phase. Four studies found no changes in concentrations of 25(OH)D. Two studies found a rise in 1,25(OH)D within the follicular phase, including a 128% increase from day 1 to 15 and a 56% increase from day 0 to 12. Two studies found rises in 1,25(OH)D concentrations from the follicular to luteal phase of 13 and 26%. Five studies did not find any changes in concentrations of 1,25(OH)D.
CONCLUSIONS
No conclusion can be drawn on the pattern of 1,25(OH)D concentrations across the normal menstrual cycle due to inconsistencies in study findings. Evidence is currently insufficient to assess 25(OH)D concentrations across the cycle. Future studies should aim to measure 1,25(OH)D and 25(OH)D longitudinally, to understand relationships with other hormones and the potential impact on estimates of vitamin D deficiency.
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