Influence of sex, body mass index and age on the results of the 2-mg overnight dexamethasone suppression test

AbstractBackground:The overnight dexamethasone suppression test (DST) is routinely used in establishing the diagnosis of Cushing’s syndrome. However, factors such as variable resorption and increased metabolism of dexamethasone (DXMS) could lead to false positive results. The aim of our study was to evaluate the influence of sex, body mass index (BMI) and age on the DXMS metabolism.Methods:In total, 183 subjects were enrolled in a regular 2 mg DST. Patients with Cushing’s syndrome, depression, renal or hepatic insufficiency and patients treated with liver enzyme modulating pharmaceuticals were excluded from this study, so that 72 patients and 66 healthy subjects were analyzed. Nocturnal blood withdrawals were performed in 11 adult subjects at 1:00 AM, 3:00 AM, 5:00 AM, 7:00 AM, 8:00 AM to evaluate the kinetic of DXMS and cortisol.Results:In the DST DXMS levels demonstrated a high variation at 8:00 AM, that was inversely correlated with BMI (r=−0.24, p=0.045). Furthermore, DXMS levels determined in patients with a BMI<30 kg/m2(n=29) were significantly higher than values of obese patients with a BMI>30 kg/m2(n=43) (1.66±0.71 ng/mL vs. 1.31±0.57 ng/mL, p=0.026). Cortisol levels, measured at the same time, were neither correlated with DXMS nor with BMI values. In the kinetic study, maximal DXMS concentration was measured at approximately 3:00 AM. At 8:00 AM, median of DXMS was reduced to 59.1% and was correlated directly with the DXMS AUC (r=0.75, p=0.013). However, there was no correlation between the cortisol levels at 8:00 AM and the nocturnal DXMS concentrations.Conclusions:In the DST BMI of individual patients could modulate the resorption rate and metabolism of DXMS but appears to have no impact on cortisol levels. Therefore, obesity should not be a cause of falsely positive results in the DST.

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Association between posttest dexamethasone and cortisol concentrations in the 1 mg overnight dexamethasone suppression test

Endocrine Connections ◽

10.1530/ec-12-0047 ◽

2012 ◽

Vol 1 (2) ◽

pp. 62-67 ◽

Cited By ~ 3

Author(s):

Bjørn O Åsvold ◽

Valdemar Grill ◽

Ketil Thorstensen ◽

Marit R Bjørgaas

Keyword(s):

Cushing’S Syndrome ◽

Plasma Cortisol ◽

Polynomial Regression ◽

Regression Line ◽

Cushing's Syndrome ◽

Dexamethasone Suppression Test ◽

Strong Negative Association ◽

Suppression Test ◽

Cortisol Levels ◽

Dexamethasone Suppression

It has been suggested that comparison of posttest dexamethasone and cortisol concentrations may improve the evaluation of the dexamethasone suppression test (DST) for Cushing's syndrome. In particular, this would be reasonable if posttest cortisol differs by dexamethasone levels within the range that is usually attained in the DST. Using fractional polynomial regression, we therefore studied the association between posttest 0800 h dexamethasone and cortisol levels in 53 subjects without Cushing's syndrome who were tested with the 1 mg overnight DST. Plasma dexamethasone was associated with plasma cortisol (P<0.001), and the regression line suggested a strong negative association related to dexamethasone levels <5 nmol/l. However, among the 94% of subjects with plasma dexamethasone >5.0 nmol/l, there was no association between dexamethasone and cortisol levels (P=0.55). In conclusion, subjects tested with the 1 mg overnight DST usually attain an 0800 h plasma dexamethasone >5 nmol/l, and plasma cortisol does not differ by plasma dexamethasone in these subjects. This suggests that routine comparison of dexamethasone and cortisol levels may not be a useful approach to improve the performance of the 1 mg DST. However, dexamethasone measurements may identify subjects with inadequately low plasma dexamethasone and may therefore be of value when retesting subjects with possibly false-positive DST results.

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SIMPLIFIED DEXAMETHASONE SUPPRESSION TEST

Acta Endocrinologica ◽

10.1530/acta.0.0610219 ◽

1969 ◽

Vol 61 (2) ◽

pp. 219-231 ◽

Cited By ~ 14

Author(s):

V. H. Asfeldt

Keyword(s):

Cushing’S Syndrome ◽

Normal Subjects ◽

Cushing's Syndrome ◽

Dexamethasone Suppression Test ◽

Clinical Value ◽

Suppression Test ◽

The One ◽

Steroid Excretion ◽

Dexamethasone Suppression

ABSTRACT This is an investigation of the practical clinical value of the one mg dexamethasone suppression test of Nugent et al. (1963). The results, evaluated from the decrease in fluorimetrically determined plasma corticosteroids in normal subjects, as well as in cases of exogenous obesity, hirsutism and in Cushing's syndrome, confirm the findings reported in previous studies. Plasma corticosteroid reduction after one mg of dexamethasone in cases of stable diabetes was not significantly different from that observed in control subjects, but in one third of the insulin-treated diabetics only a partial response was observed, indicating a slight hypercorticism in these patients. An insufficient decrease in plasma corticosteroids was observed in certain other conditions (anorexia nervosa, pituitary adenoma, patients receiving contraceptive or anticonvulsive treatment) with no hypercorticism. The physiological significance of these findings is discussed. It is concluded that the test, together with a determination of the basal urinary 17-ketogenic steroid excretion, is suitable as the first diagnostic test in patients in whom Cushing's syndrome is suspected. In cases of insufficient suppression of plasma corticosteroids, further studies, including the suppression test of Liddle (1960), must be carried out.

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