Evidence for Abnormal Vitamin B6Metabolism in Pregnancy and Various Disease States

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Abstract
Evidence for a biochemically demonstrable disturbance in the metabolism of vitamin B6 during pregnancy is based on the following observations: (1) A marked increase of xanthurenic acid excretion following a tryptophan load test. (2) An abnormal excretion pattern of tryptophan metabolites on chromatographic analysis which is strikingly similar to that described in vitamin B6-deficient rats. (3) Immediate normalization of tryptophan metabolism following the administration of relatively small amounts of pyridoxine. (4) An abnormal vitamin B6, load test indicating a significantly larger retention of the administered vitamin in comparison to non-pregnant control subjects. Some patients with hyperthyroidism, febrile diseases, and carcinoma exhibit a similar disturbance of tryptophan metabolism which responds to the administration of pyridoxine. The possible mechanism of this disturbance is discussed and certain therapeutic implications are pointed out.