Yamakita N, Gomez-Sanchez CE, Mune T, Morita H, Yoshida H, Miyazaki S, Yasuda K. Simultaneous measurement of plasma 18-oxocortisol and 18-hydroxycortisol levels in normal man. Eur J Endocrinol 1994;131:74–9. ISSN 0804–4643
Plasma 18-oxocortisol (18-oxoF) and 18-hydroxycortisol (18-OH-F) were measured in 47 healthy subjects. Plasma 18-oxoF and 18-OH-F in the early morning were 0.827 ± 0.04 nmol/l and 3.29 ± 0.175 nmol/l, respectively. The plasma levels of both steroids correlated with each other and with cortisol, but not with aldosterone. Postural stimulation with or without furosemide administration increased 18-oxoF, 18-OH-F, aldosterone and plasma renin activity (PRA). Two hours after 2 mg of oral dexamethasone administration or after an overnight 2 mg of dexamethasone suppression cortisol, 18-oxoF and 18-OH-F decreased. Cortisol, aldosterone, 18-oxo-F and 18-OH-F increased after the intravenous administration of 250 μg of 1–24 ACTH. Changes in plasma 18-oxo-F and 18-OH-F levels correlated with PRA change during the posture studies and correlated with the change of ACTH during the dexamethasone studies. The ratios of post-/pre-test values of the postural stimulation and dexamethasone suppression in 18-oxoF and 18-OH-F were lower than that of aldosterone. Plasma 18-oxoF and 18-OH-F are more dependent on ACTH than on the reninangiotensin system. The ratio of 18-OH-F/18-oxoF, which is between 4 and 5, remains constant during the various stimulation or suppression maneuvers.
Noriyoshi Yamakita, Department of Internal Medicine, Matsunami General Hospital, Kasamatsu, GifuPrefecture, 501-61 Japan