18-Hydroxycortisol and 18-oxocortisol in Cushing's syndrome

In patients with primary aldosteronism due to an aldosterone-producing adenoma and glucocorticoid-suppressible aldosteronism, 18-hydroxycortisol and 18-oxocortisol excretions are elevated. Both steroids are synthesized in the transitional zone between the zona glomerulosa and zona fasciculata. There are no reports concerning production of these steroids in Cushing's syndrome due to adrenal adenoma or hyperplasia, as far as we know. We determined the urinary excretion and serum concentration of 18-hydroxycortisol and 18-oxocortisol in eight patients with Cushing's syndrome (four due to adrenal adenoma, and four due to adrenal hyperplasia). Two of the four patients with adrenal adenoma had high levels of urinary and serum 18-hydroxycortisol and 18-oxocortisol; on the other hand all the patients with adrenal hyperplasia had normal urinary and serum levels of both steroids. Patients with high concentrations of 18-hydroxycortisol and 18-oxocortisol, however, showed no differences in clinical features, routine laboratory findings and hormonal data compared to patients with normal concentrations of 18-hydroxycortisol and 18-oxocortisol. Our data suggest that some adrenal adenomas causing Cushing's syndrome originate from transitional cells.