One microgram ACTH (adrenocorticotropin) test is considered to have higher sensitivity for early diagnosis of subclinical hypoadrenalism. In the test, the response of total serum cortisol concentration after ACTH application is evaluated. The concentration of total cortisol in serum is influenced by various diseases and drugs (containing oestrogens) that affect the concentration of cortisol binding proteins and subsequently measured cortisol levels. By routine laboratory methods, it is difficult to measure free fraction of serum cortisol. It may be overcome by determination of concentration of salivary cortisol, which is known to reflect perfectly the free hormone levels and does not depend on the intensity of saliva production.
Thirteen healthy women aged from 22 to 40 years without oestrogen therapy were investigated in follicular phase of the menstrual cycle. The response of cortisol concentration in saliva and serum was determined before, and 30 and 60 minutes after administration of 1 μg of ACTH (Synacthen 250 μg in 250 ml of 0.9% NaCl, 1 ml i.m.). In all women who underwent the test, the cortisol levels exceeded 500 nmol/l in serum and 20 nmol/l in saliva 30 minutes after ACTH application.
Statistically significant increase in both parameters in the 30th minute of the test was observed. Both levels correlated well with a coefficient r=0.631 and P value < 0.0206. Comparison of both test proved that salivary cortisol determination can serve as an adequate alternative to the serum cortisol in 1 μg ACTH test. This non-invasive sample collection and estimation of salivary cortisol reflecting its free fraction is especially advantageous for examination of adrenal function in women using oral contraceptives.