Use of Salivary Cortisol and Cortisone in the High- and Low-Dose Synacthen Test

Charlotte J. Elder; Robert F. Harrison; Alexandra S. Cross; Ruben Vilela; Brian G. Keevil; Neil P. Wright; Richard J. Ross

Disclosures

Clin Endocrinol. 2018;88(6):772-778. 

In This Article

Abstract and Introduction

Abstract

Context: Salivary cortisone reflects serum cortisol levels, is more sensitive than salivary cortisol at lower values of serum cortisol and is noninvasive.

Objective: To investigate the relationship between serum cortisol and salivary cortisol and cortisone following low– and high–dose synacthen.

Design and setting: Prospective pharmacodynamic studies in clinical research facilities.

Participants and intervention: Thirty–five dexamethasone–suppressed, healthy adult males underwent an intravenous synacthen test: N = 23 low–dose (1 mcg), N = 12 high–dose (250 mcg). Paired serum and salivary samples were taken at 15 sampling points over 120 minutes.

Main outcome measure: Serum cortisol and salivary cortisol and cortisone were analysed for correlations and by a mixed–effects model.

Results: At baseline, the correlation between serum cortisol and salivary cortisol was weak with many samples undetectable (r = .45, NS), but there was a strong correlation with salivary cortisone (r = .94, P < .001). Up to 50 minutes following synacthen, the correlation coefficient between serum cortisol and salivary cortisol and cortisone was <0.8, but both had a stronger correlation at 60 minutes (salivary cortisol r = .89, P < .001, salivary cortisone r = .85, P < .001). The relationship was examined excluding samples in the dynamic phase (baseline to 60 minutes). Salivary cortisol and cortisone showed a close relationship to serum cortisol. Salivary cortisone showed the stronger correlation: salivary cortisol r = .82, P < .001, salivary cortisone r = .96, P < .001.

Conclusion: Following synacthen, both salivary cortisol and cortisone reflect serum cortisol levels, but there is a lag in their rise up to 60 minutes. The results support further research for possible future use of a 60–minute salivary cortisone measurement during the synacthen test.

Introduction

Measurement of salivary cortisol is becoming routine in some clinics for the assessment of adrenal function. Late–night salivary cortisol testing is now recommended as a first–line diagnostic test in Cushing's syndrome,[1] and there are reports of its use in the diagnosis of adrenal insufficiency.[2–10] Advocates of salivary measurements favour its convenience and potential cost savings over serum sampling. It is noninvasive, painless, has no requirement for clinic attendance and reflects serum–free cortisol, and there is less risk of false–positive results, generated by the cortisol stress response to venipuncture, when testing for Cushing's disease. Recent evidence suggests that salivary cortisone is a better reflection of serum total and free cortisol than salivary cortisol.[2,11–13] Serum–free cortisol and salivary cortisol are rapidly oxidized to inactive cortisone, by 11β–hydroxysteroid dehydrogenase type 2 (11β–HSD–2), which is responsible for the large difference in the proportion of salivary cortisol:cortisone (1:6) compared with that in serum (4:1).[11] Salivary cortisone reflects serum cortisol levels both under physiological conditions[2] and after administration of hydrocortisone, with 94% of the variability in salivary cortisone attributable to changes in serum cortisol.[11,12] Salivary cortisone is more sensitive at low serum cortisol levels than salivary cortisol, making it better suited for the detection of adrenal insufficiency.[2,5,8,12]

Stimulation of the adrenal cortex with synthetic (1–24) ACTH (synacthen) is the standard diagnostic test for adrenal insufficiency.[9,14,15] The test involves administration of 250 mcg of synacthen, a supraphysiological dose. The low–dose synacthen test (most commonly 1 mcg) is used by some clinicians, as it is thought to more closely mimic a physiological stress stimulus to the adrenal cortex.[14] Results of meta–analyses do not show significant superiority of one test over another, and both doses are used in clinical practice.[16–20]

The measurement of salivary cortisol has been used after stimulation, with different doses of synacthen, in both healthy volunteers and patients.[3–6,8,10] The results support the use of salivary sampling after synacthen, particularly in groups with low serum steroid binding–protein levels and women on estrogens.[10,12,21] There are limited data on the use of salivary cortisone following synacthen stimulation.[5,8,12] We report the relationship of serum cortisol, salivary cortisol and salivary cortisone following administration of low– and high–dose synacthen and demonstrate the importance of sample timing.

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