Evidence supporting the renal synthesis of 19-nor-deoxycorticosterone

The fraction of urine containing free steroids was analyzed in a specimen obtained from a patient with 17 alpha-hydroxylase deficiency and contained deoxycorticosterone (DOC) (approximately 0.9 micrograms/24 h), 19 nor-DOC (approximately 1.1 micrograms/24 h) and tetrahydro-DOC (approximately 15.2 micrograms/24 h). These steroids were identified by combined gas chromatography/mass spectrometry. If present, tetrahydro-19-nor-DOC was at a concentration below the limits of detection, but it was the major metabolite found in urine of a normal person after ingestion of the steroid. This strongly suggests that little 19-nor-DOC passes through the liver after synthesis and is therefore further evidence that the final stage of its synthesis occurs in the kidney in close proximity to the site of excretion.