Endo+: Adrenocortex — Salivary Diurnal Cortisol and DHEA Profile (Genova Diagnostics)

The morning salivary cortisol measurement captures the highest point of the physiological diurnal cortisol rhythm. Cortisol is secreted in pulses by the adrenal cortex under ACTH drive from the anterior pituitary — the hypothalamic-pituitary-adrenal (HPA) axis — with the highest secretory pulse occurring in the 30–45 minutes immediately following waking, a phenomenon termed the cortisol awakening response (CAR). The CAR represents a discrete neurally-mediated amplification of the morning cortisol peak that is 50–100% higher than the waking level itself and is regulated by the suprachiasmatic nucleus circadian pacemaker, hippocampal glucocorticoid receptor feedback, and anticipatory psychological arousal. Salivary cortisol measures the free, biologically active fraction of circulating cortisol — approximately 1–3% of total serum cortisol — unaffected by cortisol-binding globulin (CBG) fluctuations that complicate serum total cortisol interpretation in patients on oestrogen therapy or with altered CBG synthesis.

The morning waking cortisol and CAR are the primary indicators of HPA axis activation status and circadian integrity. A robust morning cortisol peak and a strong CAR indicate intact hypothalamic-pituitary-adrenal axis responsiveness and appropriate circadian entrainment. A blunted or absent CAR — below the expected 50–100% post-waking rise — is a validated biomarker of HPA axis hyporesponsiveness associated with burnout, chronic fatigue syndrome, post-traumatic stress disorder, and prolonged chronic stress; it also occurs in shift workers and individuals with circadian disruption. An exaggerated CAR is associated with high anticipatory stress, anxiety disorders, early-stage HPA hyperactivation, and early-morning awakenings. In functional and integrative medicine, the morning cortisol and CAR establish the anchor point of the diurnal curve from which the remainder of the daily pattern is interpreted.

The noon cortisol measurement captures the first major decline phase of the diurnal cortisol curve, reflecting the progressive reduction in HPA axis pulsatile secretion following the morning peak under the influence of circadian-regulated hippocampal and hypothalamic glucocorticoid negative feedback. By midday, salivary cortisol has typically fallen to approximately 30–50% of the morning peak value. The rate of this morning-to-noon decline is an informative parameter — excessive noon elevation relative to morning may indicate a delayed or flattened diurnal decline pattern associated with chronic stress states, while a very rapid noon decline below the reference range suggests an early steep cortisol drop that may contribute to midday energy troughs.

The noon salivary cortisol provides the first reference point for assessing the rate and trajectory of the diurnal cortisol decline — the pattern between morning and noon is the steepest physiological slope in the cortisol diurnal curve. In functional and integrative medicine, this time point is interpreted as part of the diurnal rhythm pattern rather than in isolation. Elevated noon cortisol alongside elevated morning cortisol indicates sustained HPA axis hyperactivation — consistent with chronic psychological stress, active inflammatory disease, or hypothalamic dysregulation. Suppressed noon cortisol in a patient with fatigue and midday energy collapse suggests early diurnal cortisol insufficiency despite potentially preserved morning output.

The afternoon salivary cortisol reflects the continued physiological decline of cortisol through the second half of the active day, now at approximately 20–30% of the morning peak value. This time point sits within the zone of declining but still biologically active cortisol secretion — providing energy substrate, anti-inflammatory tone, and metabolic homeostasis for the afternoon activity period while initiating the transition toward the evening nadir. Afternoon cortisol is particularly responsive to psychological and physical stressors — acute stress at this time of day produces a proportionally larger relative rise above the low afternoon baseline than the same stressor applied in the morning.

The afternoon cortisol measurement identifies a pattern of delayed or sustained elevation that is clinically associated with chronic stress, anxiety disorders, metabolic syndrome, and insulin resistance — all conditions where cortisol remains relatively elevated through the afternoon rather than continuing its expected decline. An elevated afternoon cortisol alongside a suppressed evening cortisol suggests a compressed but still-present diurnal variation; a flattened curve where afternoon cortisol is similar to morning cortisol indicates circadian rhythm disruption. In integrative practice, afternoon cortisol is frequently the time point most responsive to stress reduction interventions, adaptogenic botanicals, and lifestyle modification.

The night salivary cortisol represents the physiological nadir of the diurnal cortisol curve — the lowest point of HPA axis output, occurring during the early hours of sleep when ACTH pulsatility is at its minimum and hippocampal glucocorticoid feedback suppression is greatest. This nocturnal suppression is essential for restorative sleep, immune consolidation, and the growth hormone secretory pulse that dominates the first third of the sleep cycle. Cortisol begins its pre-waking rise approximately 2–3 hours before habitual waking time, driven by the suprachiasmatic nucleus circadian clock in anticipation of the waking CAR. A true cortisol nadir below 0.5 ng/mL confirms intact circadian suppression.

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.

Salivary DHEA is the free, unbound fraction of circulating unconjugated DHEA that passively diffuses across the salivary gland acinar cells into saliva — reflecting the biologically active DHEA fraction available at the tissue level, analogous to salivary cortisol's relationship to serum total cortisol. Salivary DHEA follows a diurnal pattern similar to unconjugated serum DHEA — peaking in the morning — but with less pronounced diurnal variation than cortisol and substantially lower absolute concentrations. It does not reflect the stable DHEA-S pool, which requires serum measurement. DHEA serves as an anabolic counter-regulatory hormone to cortisol's catabolic and immunosuppressive effects, making the cortisol:DHEA ratio a clinically meaningful index of the balance between stress-driven catabolism and anabolic resilience.

In Genova Diagnostics' interpretive framework, salivary DHEA is assessed principally through its ratio to salivary cortisol — the cortisol:DHEA ratio — rather than as an isolated absolute value. A high cortisol:DHEA ratio indicates a predominantly catabolic, stress-dominant hormonal environment associated with accelerated biological ageing, immune suppression, muscle wasting, metabolic dysfunction, and reduced adaptive capacity. In functional and integrative adrenal assessment, this ratio is considered the key interpretive axis of the diurnal cortisol profile — a low DHEA relative to cortisol guides DHEA supplementation, adaptogenic support, and HPA axis rebalancing interventions independent of whether absolute cortisol is elevated or within range. Low DHEA alongside low cortisol across all time points suggests adrenal reserve depletion ('adrenal fatigue' in functional medicine terminology), while low DHEA with elevated cortisol suggests early-stage stress-driven catabolism with intact adrenocortical stimulation.

The cortisol:DHEA ratio is a derived index that quantifies the balance between the primary adrenocortical catabolic hormone (cortisol) and the primary adrenocortical anabolic precursor hormone (DHEA). Both are produced by the adrenal cortex under ACTH stimulation but through divergent synthetic pathways — cortisol via the zona fasciculata (17α-hydroxylase then 11β-hydroxylase) and DHEA via the zona reticularis (17,20-lyase). The ratio is influenced by the relative activity of these two synthetic pathways, which shifts with ageing (progressive decline in zona reticularis DHEA output relative to zona fasciculata cortisol output), chronic stress (ACTH predominantly stimulates cortisol over DHEA under sustained activation), and nutritional depletion.

The cortisol:DHEA ratio is the primary derived clinical parameter in Genova Diagnostics' adrenocortex interpretive report, synthesising the individual cortisol and DHEA values into a single index of the anabolic-catabolic hormonal balance. Elevated ratio (high cortisol relative to DHEA) — the dominant pattern in chronic stress, advancing age, and HPA hyperactivation — is associated with immune suppression, visceral adiposity, muscle catabolism, cognitive impairment, and reduced resilience to further stressors. It is the primary functional medicine target for adrenal support interventions: adaptogenic botanicals (ashwagandha, rhodiola), DHEA supplementation, sleep optimisation, and stress reduction. A declining ratio over serial assessments — cortisol falling and DHEA rising — is the objective treatment response target in adrenal restoration protocols.