Plasma and urinary catecholamines during the human ovulatory cycle

We measured plasma catecholamine concentrations and urinary catecholamine excretion during the ovulatory cycle in six healthy women. Plasma norepinephrine was consistently at its lowest during the follicular phase of the cycle. Plasma norepinephrine began to increase about 2 days before ovulation and continued to increase after ovulation, so that the average luteal phase NE concentration was significantly higher than the average follicular phase concentration (217 versus 143 pg/ml, p less than 0.001). Urinary norepinephrine excretion showed a similar but attenuated pattern. The results suggest that sympathetic neural activity changes with the phase of the ovulatory cycle. Cyclic patterning of plasma norepinephrine is one of many factors which should be considered in the design and analysis of studies which use plasma norepinephrine as an indicator of sympathetic neural activity in human disease states.