PURPOSE: Iron deficiency is known to affect between 15-35% of female athletes. The high prevalence has been associated with iron loss during menstruation and the influence of ovarian hormones on iron absorption. The aim of this study was to examine changes to markers of iron status and regulation across the menstrual cycle and over an intensified training period.
METHODS: Twenty-four highly trained First Nation’s athletes from the National Rugby League’s Indigenous Women’s Academy attended a 5-week training camp at the Australian Institute of Sport. Athletes were either naturally cycling (NC; n=11) or using hormonal contraception (HC; n=4 combined oral contraceptive pill (OCP), n=8 implant, n=1 injection). Fasted venous blood samples were collected during Phase 1 (menstruation), Phase 2 (late follicular) and Phase 4 (mid-luteal) of the menstrual cycle in NC athletes for determination of markers of iron status. In athletes using HC, three equally spaced, corresponding time points were selected for sampling, which avoided the withdrawal bleed in athletes using OCP. Every 48 h during the training camp (14 measures over 27 days), a fasting capillary blood sample was collected and analysed for serum ferritin (sFer) and hepcidin. Where venous and capillary measurement dates aligned, samples were simultaneously collected and analysed to confirm the agreement between collection methods.
RESULTS: No differences across phases or between menstrual status groups were evident for sFer, transferrin or haemoglobin (p>0.05). Serum iron showed a significant interaction effect (p=0.043), where a small increase in serum iron was seen from Phase 1 to Phase 2 in NC athletes (3.9 µg/L; 30%), which corresponded with a decrease in HC users (4.0 µg/L; -21%). Capillary sampling for the measurement of sFer (r=0.91 [0.80-0.96]; p<0.001) and hepcidin (r=0.99 [0.97-0.99]; p<0.001) was similar to venous blood sampling. When sampled every 48 h, sFer (p<0.001) and hepcidin (p<0.001) concentrations declined significantly across the training camp. No differences were observed between NC athletes and those using HC for either sFer (p=0.465) or hepcidin (p=0.656).
CONCLUSION: While mechanistic evidence suggests that ovarian hormones and menstruation can affect iron metabolism, our study showed limited impact of the menstrual cycle on markers of iron regulation, with the impact of training being far more pronounced, likely overshadowing any impact of the menstrual cycle. Implications of this work suggest that athletes do not need to implement additional control for menstrual cycle phase when screening and monitoring iron status. Our data highlight the need for practitioners to interpret changes in iron status relative to current training volumes and erythropoietic requirements. Finally, this work describes a novel, accurate, minimally invasive methodology for testing iron parameters in the field, which may improve future iron deficiency prevention strategies in team sport settings.
Disclosures: This study was embedded within the Female Athlete Research Camp, and was co-funded by Australian Catholic University, Wu Tsai Human Performance Alliance and the Australian Institute of Sport Female Athlete Performance and Health Initiative.
