The Variations in Urinary Aldosterone Levels of Normal Females During Their Menstrual Cycle

Summary In a series of six subjects studied, a day‐to‐day fluctuation in urinary aldosterone excretion with a definite and characteristic pattern throughout the menstrual cycle was noted in all. The excretory level was lowest (mean value 8·5 μg. per 24 hours) 25 to 17 days before menstruation, with an increase (mean value 11 μg. per 24 hours) 17 to 14 days prior to menstruation. An increase in excretion was again noticed in the second half of the cycle, with a peak excretion (mean value 23 μg. per 24 hours) one to five days before menstruation. This was followed in most subjects by a sharp decrease in excretion one to two days before menstruation. During the first day of menstruation a relatively low level was found, followed in some subjects by an increase on certain days of menstruation. The urinary sodium‐potassium concentration ratio fluctuated during the menstrual cycle with no direct relationship to aldosterone levels. The lowest urinary sodium‐potassium ratios were found in specimens one to five days before menstruation. A premenstrual increase in body weight ranging from 0·5 to 2·3 kg., with the maximum three to one days prior to menstruation, was noted in five subjects. This weight increase either followed or preceded the maximum observed aldosterone excretion. In one post‐menopausal subject observed over a period of 26 days, the urinary aldosterone excretion ranged from 8·5 to 14 μg. per 24 hours. A detailed description of a chemical method for estimation of aldosterone in urine is given.