Salivary cortisol measurements for reliable numerical maximum concentration after the low dose 1 µg ACTH intravenously in healthy individuals

Abstract We examined the potential use of the 1 µg adrenocorticotropic hormone (ACTH) stimulation test to identify the optimal timing for measuring the maximum response after stimulation and to assess whether salivary cortisol might replace serum cortisol at that time. Data were collected from a trial investigating yoga as a stress management intervention. We recruited healthy, working participants experiencing stress ( n = 36, including 8 men), aged 25–62, from the healthcare sector. We obtained simultaneous serum and salivary cortisol samples six times over 60 min following an intravenous injection of 1 µg ACTH. Data were analyzed with the Fisher-Pitman permutation test and the general estimation equation. Most peak responses in serum and saliva occurred at 30 and 40 min. Additionally, the median maximum response values at these times were similar to the medians across all sampling times ( P = 0.1 and P = 0.06, respectively). Cortisol response curves in serum and saliva were parallel at 30–40 min ( P = 0.83). Salivary cortisol may substitute for serum cortisol in the 1 µg ACTH stimulation test to assess maximum stress-response capacity in people at risk for stress-related disorders, as in this study, with sampling only at 30 and 40 min.