Cyclical fluctuations of iron biomarkers in women: Diagnostic implications for iron deficiency.
Level 4 - case-series / case-control
Cross-sectional observational analysis of survey data
PubMed 41362311 · doi:10.1016/j.plabm.2025.e00512
What was done
Analyzed cross-sectional data from 1,484 non-pregnant women aged 18–44 years from the 2003–2006 NHANES database. Participants were categorized by menstrual cycle phase based on recall: menstruation (days 1–5), follicular phase (days 6–15), early/mid-luteal phase (days 16–23), and late luteal phase (days 24–35). The authors evaluated phase-specific differences in eight iron biomarkers (serum iron [SI], transferrin saturation [%TS], soluble transferrin receptor [sTfR], ferritin, erythrocyte protoporphyrin [EPP], hemoglobin [Hb], mean corpuscular volume [MCV], and body iron index [BII]) and assessed iron deficiency (ID) and iron deficiency anemia (IDA) prevalence using survey-weighted models.
What was found
SI and %TS were lowest during menstruation and peaked in the early/mid-luteal phase (SI: p = 0.001; %TS: p = 0.003). sTfR was highest during menstruation (p < 0.05). Ferritin, EPP, Hb, and MCV showed no significant variation across phases. ID prevalence ranged from 10.5% to 22.0% across different diagnostic models without consistent phase differences. In contrast, composite IDA prevalence dropped significantly from 7.5% during menstruation to 3.7% in the late luteal phase (p = 0.033).
Why it matters
Circulating iron measures and IDA diagnosis fluctuate across the menstrual cycle, whereas ferritin remains stable. Considering menstrual phase during clinical testing could reduce misclassification of iron deficiency anemia in reproductive-aged women.
Limits
The study is cross-sectional, comparing different women across cycle phases rather than tracking longitudinal within-person changes. Cycle phases were estimated from reported days rather than confirmed by hormone profiling. The abstract provides no data on hormonal contraceptive use, cycle regularity, or menstrual blood loss volume.
Cited by
- supports Between 20% and 30% of menstruating women are iron deficient during menstruation.