Effect of single doses of dexamethasone and adrenocorticotrop hormone on serum bone markers in healthy subjects and in patients with adrenal incidentalomas and Cushing's syndrome.

The aim of the present study was to explore whether short-term changes in glucocorticoid activity which occur during dynamic testing of the pituitary adrenal axis with dexamethasone, ACTH, or metyrapone could have an effect on serum osteocalcin (OC) and beta-crosslaps (beta-CTx) concentrations in healthy subjects, in patients with adrenal incidentalomas and in those with Cushing's syndrome. The study included 40 healthy subjects (35 women and 5 men, age range 18-69 yr), 49 patients with adrenal incidentalomas (34 women and 15 men, age range 19-77 yr) and 8 patients with Cushing's syndrome (5 cortisol-producing adenomas and 3 pituitary-dependent Cushing's syndrome, 3 women and 5 men, age range 19-70 yr). Serum OC and beta-CTx concentrations were determined with electrochemoluminescent immunoassays at midnight, after an overnight fast between 08:00 and 09:00 h, after an overnight dexamethasone test (1 mg, orally) and after a single dose of metyrapone (30 mg/kg, orally). In healthy subjects and in patients with adrenal incidentalomas, serum bone marker concentrations were also measured after a single dose of ACTH injection (Cortrosyn depot, 1 mg im). Patients with Cushing's syndrome, but not those with adrenal incidentalomas, showed significantly lower serum OC at midnight (18.5+/-12 ng/ml, mean+/-SD) and between 08:00 and 09:00 h (17.7+/-9.6 ng/ml) compared to corresponding values obtained in healthy subjects (24.5+/-7.0 and 28.3+/-12.2 ng/ml, respectively). Serum OC concentrations were significantly decreased after a single dose of 1-mg dexamethasone in healthy subjects (from 28.3+/-12.2 to 21.8+/-9.5 ng/ml) and in patients with adrenal incidentalomas (from 29.8+/-15.9 to 24.1+/-14.1 ng/ml), whereas serum OC concentrations remained unchanged in patients with Cushing's syndrome. In addition, serum OC concentrations were even more markedly decreased after a single dose of ACTH injection in both healthy subjects (12.5+/-4.6 ng/ml) and in patients with adrenal incidentalomas (12.2+/-6.5 ng/ml). By contrast, metyrapone administration failed to induce significant changes in OC levels. There were no significant differences in beta-CTx concentrations between the three groups or after drug treatments. Thus, serum OC levels should be interpreted with caution when obtained during testing of the pituitary-adrenal axis with dexamethasone or ACTH.