Cyclical Cushings syndrome is typically detected by collecting sequential daily early morning urine (EMU) samples for cortisol to creatinine ratio over a 28 day period. More recently nocturnal salivary cortisol (NSC) measurement has been shown to be a sensitive means of screening for Cushings syndrome. The Endocrine Society have suggested that NSC may be used to assess patients for cyclical Cushings however there is limited evidence that it correlates with the present standard of EMU testing or that it demonstrates a cyclical pattern over 28 days. In this study we sought to correlate NSC with EMU results collected the following morning and to determine whether NSC could be used to detect cycles in patients with cyclical Cushings syndrome. A sequential 28 day collection of NSC and EMU was performed on 11 occasions in ten patients with confirmed or suspected Cushings syndrome. One patient with cyclical Cushings completed the collection both before and after cabergoline therapy. Seven collections were from patients with active Cushings disease (3 with cyclical form), three were from patients in remission (1 with cyclical Cushings and 2 with clinical features suspicious of recurrence) and one was from a patient eventually shown not to have hypercortisolism. In total there were 270 matched salivary and urinary results. The Spearmans rank correlation coefficient was 0.79 (P=<0.001). In two patients with cyclical Cushings, EMU and NSC followed a similar cyclical pattern. In one patient with recurrent cyclical Cushings, cortisol was elevated in both saliva and urine but with more prominent cycles in saliva. We found that NSC correlated reasonably well with EMU collected the following morning. NSC detected all three cases of cyclical Cushings. If these results are replicated in larger numbers NSC may prove to be an additional option or replacement for EMU in detecting cyclical Cushings syndrome.
Declaration of interest: There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.
Funding: No specific grant from any funding agency in the public, commercial or not-for-profit sector.