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Aim:Although the peak cortisol response in the low-dose test does not reach the generally accepted value of 18 μg/dL, there are many patients whose adrenal insufficiency diagnosis was ruled out by getting an adequate response with the standard-dose test. Thus, the standard-dose adrenocorticotropic hormone (ACTH) stimulation test is unnecessarily applied to many patients. This study aims to compare low- and standard-dose ACTH stimulation tests in diagnosing adrenal insufficiency and to determine a new optimal threshold level for low-dose ACTH stimulation tests to avoid unnecessary standard-dose ACTH tests.Methods:In this single-center cross-sectional study, patients with suspected adrenal insufficiency who underwent low-dose (1 mcg) and standard-dose (250 mcg) ACTH stimulation tests were evaluated. Cases were separated into two groups: (I) inadequate cortisol response (

The ACTH (adrenocorticotropic hormone) stimulation test is the gold standard for the diagnosis of adrenal insufficiency (AI), performed with ACTH high dose (HDT) or low dose (LDT). As salivary cortisol has been proposed as an alternative to serum cortisol, our aim was to evaluate the reliability of salivary cortisol compared to serum cortisol for diagnosing AI in children. Data were collected retrospectively. Salivary and serum cortisol values derived by 80 ACTH stimulation tests were obtained (39 F, 36 M; median age 11.5 years, IQR 6.9). Sampling was performed at baseline and after 30 and 60 min from ACTH administration during the HDT, and at baseline and 10, 20, 30, 40 and 60 min after the stimulation for the LDT. A serum cortisol level > 420 nmol/L ruled out AI. The correlation coefficients between serum and salivary cortisol for the HDT (n = 24) were 0.80 at t0, 0.48 at t30 and 0.75 at t60. All patients were adrenal sufficient. In 41% of the LDT, peak serum cortisol indicated insufficient adrenal function. The correlation coefficients between serum and salivary cortisol were 0.59 at t0 and 0.33 at the peak. For a cut-off of salivary cortisol < 15 nmol/L, sensitivity was 73.9% and specificity 69.6%. Our data do not support salivary cortisol as a valid alternative to serum cortisol during LDT. Regarding the HDT, results are more encouraging, however, further studies are needed.