This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Hepcidin is a recently discovered iron regulatory hormone produced by hepatocytes. It controls the level of extracellular iron and is essential for normal iron homeostasis. Hepcidin production is stimulated by inflammation (especially interleukin-6 [IL-6]. Recent investigations have suggested that the luteal phase of the menstrual cycle is characterized by upregulation of inflammatory cytokines in the vascular compartment. We are aware of no work to date that addresses whether hepcidin levels are affected by menstrual cycle phase. If so, a new imperative would be established to control for menstrual cycle phase in research involving measurements of hepcidin levels in pre-menopausal females. We propose that urinary hepcidin levels fluctuate according to menstrual cycle phase. Healthy females ages 18-30 with regular menstrual cycles of 28-30 days and who are not utilizing hormonally based birth control methods will be studied at three time points during one month: days 2-4 (early follicular phase), days 11-13 (late follicular phase), and days 21-23 (mid-luteal phase). Urinary hepcidin levels will be measured, and phase of menstrual cycle will be confirmed with measurement of 17-beta estradiol and progesterone.