Expanding the use of salivary cortisol as a non-invasive outpatient test in the dynamic evaluation of suspected adrenal insufficiency

Background

Adrenal insufficiency (AI) is potentially life-threatening, and accurate diagnosis is crucial. The first-line diagnostic test, the adrenocorticotrophic hormone (ACTH) stimulation test, measures serum total cortisol. However, this is affected in states of altered albumin or cortisol-binding globulin levels, limiting reliability. Salivary cortisol reflects free bioactive cortisol levels and is a promising alternative. However, few studies are available, and heterogenous methodologies limit applicability.

Methods

This study prospectively recruited 42 outpatients undergoing evaluation for AI, excluding participants with altered cortisol-binding states. Serum (immunoassay) and salivary (liquid chromatography tandem mass spectrometry) cortisol levels were sampled at baseline, 30 min, and 60 min following 250 µg synacthen administration. AI was defined as a peak serum cortisol level <500 nmol/L in accordance with guidelines.

Results

The study recruited 21 (50%) participants with AI and 21 without AI. There were no significant differences in baseline characteristics, blood pressure, or sodium levels between groups. Following synacthen stimulation, serum and salivary cortisol levels showed good correlation at all timepoints (R2 = 0.74, P < 0.001), at peak levels (R2 = 0.72, P < 0.001), and at 60 min (R2 = 0.72, P < 0.001). A salivary cortisol cut-off of 16.0 nmol/L had a sensitivity of 90.5% and a specificity of 76.2% for the diagnosis of AI.

Conclusion

This study demonstrates a good correlation between serum and salivary cortisol levels during the 250 µg synacthen test. A peak salivary cortisol cut-off of 16.0 nmol/L can be used for the diagnosis of AI. It is a less invasive alternative to evaluate patients with suspected AI. Its potential utility in the diagnosis of AI in patients with altered cortisol-binding states should be further studied.

Evaluation of the hypothalamic-pituitary-adrenal axis function in childhood and adolescence

The hypothalamic-pituitary-adrenal (HPA) axis plays an important role in the maintenance of basal and stress-related homeostasis. The hypothalamus controls the secretion of adrenocorticotropic hormone (ACTH) from the anterior pituitary, which in turn stimulates the secretion of glucocorticoids from the adrenal cortex. Glucocorticoids, the final effectors of the HPA axis, regulate a broad spectrum of physiologic functions essential for life and exert their effects through their ubiquitously distributed intracellular receptors. Alterations in the activity of the HPA axis may present with symptoms and signs of glucocorticoid deficiency or excess. Detailed endocrinologic evaluation is of primary importance in determining the diagnosis and/or etiology of the underlying condition. We review the most common endocrinologic investigations used in the evaluation of the HPA axis integrity and function.

Adrenocortical suppression increases the risk of relapse in nephrotic syndrome

OBJECTIVE

Children with nephrotic syndrome (NS) are usually treated with long-term low dose alternate day prednisolone with or without glucocorticoid sparing therapy, such as levamisole or ciclosporin, to maintain remission. The degree of hypothalamic-pituitary-adrenal axis (HPA) suppression with such therapeutic strategies has not been studied systematically. HPA suppression could cause a relapse or adrenal crisis.

STUDY DESIGN

To study the risks of HPA suppression, a modified low dose synacthen test (0.5 mug) was administered to 32 patients (22 male,10 female) with a mean age of 9.7 years (range 3.8-17.6 years) with NS receiving long-term alternate day prednisolone for over 12 months. Twelve patients received alternate day prednisolone, 11 alternate prednisolone+levamisole and nine alternate prednisolone+ciclosporin. All patients were followed up for 3 years and the relapse rate noted.

RESULTS

20/32 (62.5%) patients had a peak serum cortisol concentration of <500 nmol/l, which suggested suboptimal cortisol secretion and possible HPA suppression. 10/12 children in the prednisolone group and 8/11 in the levamisole group had a suboptimal cortisol response compared with 2/9 in the ciclosporin group. During follow-up, the 20 children who had a suboptimal cortisol response had significantly more relapses (95 relapses) compared to the 12 children with a normal cortisol response who had 24 relapses (p = 0.01).

CONCLUSIONS

Children with NS receiving long-term alternate day prednisolone therapy are at risk of developing HPA suppression and should be evaluated using the modified synacthen test. Children with evidence of HPA suppression are at a greater risk of relapse.