MedicineEndocrinologyPharmacologyHormone BiochemistryReproductive EndocrinologySteroid BiochemistryGonadal EndocrinologyGonadal HormonesMenopause Hormone TherapyCumulative Urinary ExcretionEstradiol PhysiologyEstrogen ImmunomodulationEstrogen MetabolitesEstrogen PharmacologyPyridoxine MetabolismTryptophan MetabolismUrinary Excretion Kinetics
Urinary excretion of 3-hydroxykynurenine xanthurenic acid and 3-hydroxyanthranilic acid following a trytophan load (5 gm orally) was studied in 22 normal subjects 12 women taking estrogen-progestogen preparations and 5 patients receiving estrogen alone. 3-hydroxykynurenine and 3-hydroxyanthranilic acid were measured by column chromatography and xanthurenic acid was determined by thin-layer chromatography. The excretions of 3-hydroxykynurenine and xanthurenic acid were high in both groups of hormone treated subjects. In some instances the 3-hydroxyanthranilic acid levels were also raised. Large doses of pyridoxine (20 mg orally twice daily for 6 days or 1 mg/day for 15 days then 20 mg following another tryptophan load plus another 20 mg pyridoxine) caused the high excretions to return to normal or near normal in the 3 subjects studied. It was suggested that these findings indicate an estrogen-induced increase in the capacity for conversion of tryptophan to nicotinic acid. As a result tryptophan loading produces a relative shortage of pyridoxal phosphate coenzyme with a corresponding increase in the urinary excretion of 3-hydroxykynurenine and xanthurenic acid.(AUTHORS MODIFIED)