Effect of o, p'-DDD on Cortisol Metabolism in Cushing's Syndrome of Various Etiology

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Effects of o, p'-DDD on parameters of cortisol metabolism were studied in 3 patients with Cushing's syndrome (ectopic ACTH-syndrome, Cushing's disease, and adrenal cancer). Before o, p'-DDD treatment, plasma cortisol, urinary 17OHCS, and urinary free cortisol were elevated in all patients. These parameters correlated well with each other in ectopic ACTH-syndrome and Cushing's disease. However, in adrenal cancer, urinary 17OHCS did not correlate with either plasma cortisol or urinary free cortisol, while the latter two parameters did. During o, p'-DDD, urinary 17OHCS rapidly declined in a patient with ectopic ACTH syndrome and a patient with Cushing's disease before plasma cortisol or urinary free cortisol decreases. Consequently the positive correlations of urinary 17OHCS with the other parameters were lost. In a case of adrenal cancer, urinary 17OHCS again did not correlate with plasma cortisol or urinary free cortisol. In these conditions, plasma cortisol and urinary free cortisol still significantly correlated.
The present results demonstrated the limit of urinary 17OHCS as the index of the cortisol secretion rate both in some cases of adrenal cancer and in patients taking o, p'-DDD. It is suggested that urinary free cortisol should be utilized as a more accurate index for the cortisol secretion rate in such circumstances.