PERIPHERAL HEMODYNAMICS AND RENAL-FUNCTION IN RELATION TO THE MENSTRUAL-CYCLE

1. The objective of this study was to investigate whether the luteal p hase of the menstrual cycle differs from the follicular phase by the d evelopment of a state of general vascular relaxation. 2. Once in the f ollicular and once in the luteal phase of the menstrual cycle, we meas ured by non-invasive techniques: arterial blood pressure (by finger bl ood pressure measurements), vascular tone (by pulse-wave velocity and plethysmography), blood flow to skin (by laser-Doppler), blood flow to forearm (by plethysmography) and blood flow to kidneys (by para-amino hippurate clearance), and the glomerular filtration rate (by inulin cl earance). The data points obtained in the luteal phase were compared w ith those in the follicular phase by non-parametric tests. 3. Arterial blood pressure, vascular tone and the blood flows to the forearm and kidneys were comparable in the two phases of the menstrual cycle, In c ontrast, the blood flow to the skin was consistently lower, and the gl omerular filtration rate higher in the luteal phase of the menstrual c ycle. 4. The results of the present study do not support our hypothesi s of a general vascular relaxation in the luteal phase of the menstrua l cycle. The lower skin flow in the luteal phase may be an adaptation needed to ensure the higher core temperature of 0.3-0.5 degrees C in t he luteal phase. The higher glomerular filtration rate was in most cas es paralleled by a higher renal blood flow in the luteal phase. This s uggests that the higher glomerular filtration rate is secondary to a s elective vasorelaxation of the afferent renal arterioles.