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February 21, 1966

Cyclic Fluctuation of Sweat Electrolytes in WomenEffect of Polythiazide Upon Sweat Electrolytes

JAMA. 1966;195(8):629-635. doi:10.1001/jama.1966.03100080069018

Spontaneous fluctuations in sweat electrolyte levels were studied in 57 women, including 21 mothers of children with cystic fibrosis (C/F mothers), and in nine men, to determine the effect of the menstrual cycle upon sweat salinity and to see if differences were apparent between C/F heterozygotes and controls. Sweat sodium and chloride concentrations, but not potassium, followed a cyclic pattern in 50% of the premenopausal women. The cyclic fluctuations appeared to follow the known hormonal pattern of the menstrual cycle with both "ovulatory" and "premenstrual" peaks of sweat salinity. Oral administration of a thiazide diuretic prevented or reversed the cyclic rise in sweat salinity, suggesting that the cyclic phenomenon is related to salt and water retention during the menstrual cycle. A single "sweat test" is inadequate for the detection of genetic heterozygotes for cystic fibrosis, because of the variability of sweat salinity. A greater percentage of C/F mothers had occasional sweat chloride determinations above 40 mEq/L than did the controls. Persistently high sweat salinity in an adult may be an indication of the genetic abnormality.