Endothelial function across the menstrual cycle as assessed in naturally cycling women by three relevant techniques
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This project is the first attempt to determine whether the menstrual cycle hormones have an effect on female blood vessel function as measured by two recently proposed tests of vessel reactivity. The larger implications of this study will impact future clinical research, in terms of subject preparation. Specifically, if it is found that young, healthy, naturally menstruating female subjects' blood vessel reactivity is affected by the cyclical fluctuation of the hormones estrogen and progesterone, then future research using these two new techniques should study female subjects according to the findings of this project. Namely, subjects should be studied during the menstrual cycle phase that elicits the lowest overall response when compared to the two other menstrual cycle phases observed, as this is indicative of the lowest augmentation of the results by the effect of the hormones. This is important because it is necessary to control for as many variables as possible in order to ensure confidence in the results of a study. Blood vessel function in this study will be assessed using three techniques that monitor changes in blood flow and diameter by way of ultrasound imaging. Using ultrasound, a blood vessel’s resting diameter can be quantified, and then a test can be performed in order to quantify the effect of that test of the size of the blood vessel. The amount a blood vessel “dilates,” or increases in size, is a measure of the health of the blood vessel; in general, the larger the percent change in size, the healthier the blood vessel is. The female hormones have been shown to improve blood vessel dilation when assessed by a long-used technique known as “flow-mediated dilation,” but it has not yet been determined whether other tests of vessel function, such as a hand grip model or a passive limb movement model, are similarly affected. Thus, this study seeks to determine the relationship between these hormones and these three tests of vessel function, using flow mediated dilation as a barometer for the results observed.