Studies on Tryptophan Metabolism in Male Subjects Treated with Female Sex Hormones

ABSTRACT The effect of an anovulatory drug, estrogens or gestogens on tryptophan metabolism was studied in human male subjects with prostatic diseases. Estrogens were found to increase urinary excretion of tryptophan metabolites (xanthurenic acid, kynurenic acid, kynurenine, acetylkynurenine and 3-hydroxykynurenine) following a loading dose of 2 g l-tryptophan. Estrogens were also found to enhance the conversion of the loading dose of tryptophan to urinary metabolites of nicotinic acid (N-methyl-nicotinamide and N-methyl-2-pyridone-5-carboxamide). These changes occurred after one week of treatment. A gradual rise in urinary excretion of tryptophan metabolites was seen as estrogen medication was extended, after 5 months of treatment reaching a level that is seen in severe vitamin B6 deficiency. Supplementation with vitamin B6 normalized urinary excretion of tryptophan metabolites. The effect on the conversion of tryptophan to urinary metabolites of nicotinic acid was independent of the length of estrogen m...