Optimizing Iron-Deficiency Screening for Female Athletes: Do We Need to Consider the Menstrual Cycle?

We examined factors that inform iron-deficiency screening practices in female athletes, with a focus on the menstrual cycle. Twenty-four National Rugby League athletes attended a 5-week training camp (age 21.6 ± 3.4 years old, body mass: 76.3 ± 12.1 kg, height: 164.9 ± 4.6 cm). Athletes were either naturally cycling (athleteNC; n = 11) or using hormonal contraception (athleteHC; n = 13). Venous blood samples were collected during Phases 1, 2, and 4 of the menstrual cycle in athleteNC for determination of iron status. Three equally spaced, corresponding time points were sampled in athleteHC. Every 48 hr, a capillary blood sample was collected and analyzed for ferritin, hepcidin, creatine kinase, and C-reactive protein. No differences across menstrual phases or groups were evident for ferritin, hepcidin, transferrin or hemoglobin (p > .05). Serum iron (12.9 ± 4.6 μmol/L to 16.9 ± 8.5 μmol/L; p = .045) and transferrin saturation (17.3% ± 7.8% to 22.1% ± 14.5%; p = .041) increased from Phase 1 to Phase 2 in athleteNC only, with no change seen in athleteHC. Ferritin (-16%; p < .001) and hepcidin (-23%; p < .001) declined across the training camp in all athletes. Concentrations of C-reactive protein (p = .039) were consistently higher in athleteHC compared with athleteNC, whereas creatine kinase activity were similar between groups (p = .140). Our findings did not identify clear menstrual cycle phase-related differences in markers of iron status or regulation, suggesting that the influence of cycle phase may be relatively small compared with other sources of variation. Practitioners should be mindful that athletes using hormonal contraceptives may report with greater C-reactive protein concentrations than naturally cycling athletes.