Tryptophan pyrrolase induced in human liver by hydrocortisone: effect on excretion of kynurenine.

Administration of hydrocortisone causes two- to fourfold increase in the level of activity of tryptophan pyrrolase in human liver, as measured in needle-biopsy specimens. Correlation of the higher levels of the enzyme with the amounts of urinary kynurenine suggests that the tryptophan pyrrolase level, which is regulated by adrenocortical hormones, may be the important variable in the increased excretion of tryptophan metabolites that accompanies various diseases.