Low-dose ACTH (1 µg) salivary test: a potential alternative to the classical blood test

Summary Objectives Salivary cortisol is unaffected by cortisol binding globulin (CBG) and hence allows CBG‐related variations in serum total cortisol to be bypassed. We assessed whether or not salivary cortisol can be used for the low‐dose (1 µg) ACTH test in subjects with presumed normal and elevated levels of CBG. Patients/methods We measured serum and salivary cortisol responses to intravenous administration of 1 µg ACTH in 14 healthy volunteers, 14 ‘hyperoestrogenic’ women [in their first or early second trimester of pregnancy, using oral contraceptives (OC) or on hormone replacement therapy (HRT)] and 10 patients with secondary hypoadrenalism. Cortisol levels were recorded before as well as 30 and 60 min (+30; +60 min) after ACTH administration. Results Baseline salivary cortisol did not differ significantly between the hypoadrenal and healthy patients (7·11 ± 1·4 and 12·13 ± 1·59 nmol/l; P = 0·48) but there was a significant difference between hypoadrenal and hyperoestrogenic patients (18·94 ± 3·44 nmol/l; P = 0·01). The largest difference between hypoadrenal patients and healthy individuals was observed at +30 min (9·16 ± 2·8, 52·65 ± 8·78 and 48·81 ± 6·9 nmol/l, in the hypoadrenal, healthy and hyperoestrogenic patients, respectively; P