The dexamethasone suppression test and long-term contraceptive treatment: measurement of ACTH or salivary cortisol does not improve the reliability of the test
Nickelsen, T.; Lissner, W.; Schöffling, K.
Experimental and Clinical Endocrinology 94(3): 275-280
1989
ISSN/ISBN: 0232-7384 PMID: 2560985 DOI: 10.1055/s-0029-1210910Document Number: 379685
Endocrinologists from University Hospital in Frankfurt, West Germany, compared data on 19 women 20-36 years old who had taken oral contraceptives (OCs) for at least 4 months before the study (cases) with those of 12 age matched women who took no OCs for at least 6 months before the study (controls). The goal of the study was determine the reliability of total cortisol, unbound salivary and serum cortisol, and adrenocorticotropic hormone (ACTH) parameters in the dexamethasone (2mg) suppression test under conditions of chronically high estrogen levels due to OC use. Radioimmunoassay techniques were used to measure baseline and post-dexamethasone levels of all parameters. Equilibrium dialysis was used to measure unbound serum cortisol. The mean baseline levels for all parameters were considerably greater in the cases than in the controls: total serum cortisol (32.7 mcg/dl vs. 15.6mcg/dl; p .001), free salivary cortisol (9.6ng/ml vs. 5.6ng/ml; p .01), ACTH (50.8pg/ml s. 34.2pg/ml; p .05), and free serum cortisol (6.3 mg/ml vs. 4.2 ng/ml; p .01). This suggested that estrogens exert a direct stimulatory effect on the corticotroph axis separate from a corticosteroid-binding globulin mediated increase of total cortisol. TOtal and free salivary cortisol levels after the dexamethasone suppression test for the 1 groups were not statistically significant (2.3 mcg/dl vs. 1.7 mcg/ml vs. 1.1ng/ml, respectively). On the other hand, ACTH suppression was significantly better for cases than it was for controls (2.2pg/ml vs. 5.3 pg/ml; p .001). These data indicate that post-dexamethasone measurements of ACTH or free cortisol in women taking OCs are not needed since total cortisol measurements provide the information needed. Therefore physicians should not use the dexamethasone suppression test to diagnose Cushing's disease in women using OCs.