Tryptophan Metabolism in Women Using Steroid Hormones for Ovulation Control

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Abstract
Ten women using steroid hormones for ovulation control were studied for urinary excretion levels of tryptophan metabolites before and after the ingestion of a 2-g loading dose of tryptophan. The subjects took 2.5 mg of norethynodrel and 0.1 mg of mestranol (Enovid-E) daily from the 5th through the 24th day of the menstrual cycle. After the initial study, the subjects were given 25 mg of pyridoxine hydrochloride four times daily during the 48 hr required to repeat the tryptophan loading test. Basal excretion levels (before tryptophan loading) of urinary tryptophan metabolites were normal, but after the loading dose of the amino acid the pattern of tryptophan metabolites was very abnormal as compared with that of the 18 female controls. The mean excretion level for xanthurenic acid after tryptophan loading was 697 µmoles for the subjects ingesting Enovid-E compared with about 30 µmoles for the controls. The other metabolites that were excreted in increased amounts were, in order of decreasing quantities, 3-hydroxykynurenine, kynurenine, kynurenic acid, and acetylkynurenine. Pyridoxine supplementation almost completely corrected the metabolic disorder. These results appear to demonstrate another metabolic interrelationship between steroid hormones and pyridoxine. The widespread use of steroid hormones for ovulation regulation should be considered in human metabolic studies with females, especially if pyridoxine-requiring enzyme systems are involved.