What does the Salivary Cortisol — Night (bedtime) test measure?

Why is Salivary Cortisol — Night (bedtime) measured?

Elevated night cortisol is one of the most clinically significant findings in the Endo+: Adrenocortex profile. A night cortisol above the upper reference limit indicates failure of the normal evening-to-night HPA axis suppression — associated with insomnia and sleep initiation difficulty (cortisol opposes the soporific effect of melatonin), visceral adiposity and metabolic syndrome (chronic nocturnal cortisol elevation promotes central fat deposition and insulin resistance), hypothalamic-pituitary-adrenal axis hyperactivation from chronic psychological stress, and should prompt consideration of Cushing's syndrome exclusion when markedly elevated. The late-night salivary cortisol is, in fact, the most sensitive single screening test for hypercortisolaemia — recommended by the Endocrine Society as a first-line Cushing's syndrome screening tool — making it the highest-stakes individual time point in the panel for mainstream clinical significance.

Reference ranges

Standard reference

0.1–0.5 ng/mL (0.3–1.4 nmol/L) # REVIEWER FLAG: Confirm Genova Diagnostics reference range and collection window for night/bedtime salivary cortisol — typically collected between 22:00 and 24:00 hours or at the patient's habitual bedtime. Confirm exact window in the Genova Diagnostics collection kit.

Functional medicine optimal

<0.3 ng/mL (functional medicine optimal for robust circadian suppression and sleep quality). # REVIEWER FLAG: The Endocrine Society Cushing's screening cut-off for late-night salivary cortisol is laboratory-specific — confirm Genova Diagnostics' specific upper limit and whether it aligns with their Cushing's screening threshold.

Units

ng/mL, nmol/L

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.