Why we measure it

The distinction between acute and chronic cortisol elevation is central to understanding its clinical relevance. Transient cortisol elevation during acute stress is physiologically normal and largely benign. Chronic elevation — sustained over months or years through psychological stress, sleep deprivation, shift work, visceral obesity, or HPA axis dysregulation — produces a cascade of adverse downstream effects. Chronically elevated cortisol promotes insulin resistance by blocking insulin signalling in peripheral tissues and stimulating hepatic gluconeogenesis, driving hyperglycaemia and eventually type 2 diabetes. It promotes visceral fat deposition specifically — and visceral fat itself elevates cortisol through local 11β-HSD1 enzymatic activity, creating a self-amplifying cycle. It suppresses immune competence, impairs hippocampal neurogenesis (contributing to memory consolidation failure and mood disruption), raises blood pressure through mineralocorticoid receptor cross-reactivity, reduces bone mineral density, and suppresses anabolic hormones including testosterone and IGF-1. Population studies have consistently linked higher morning cortisol levels and flattened diurnal cortisol slope to elevated cardiovascular risk, cognitive decline, and all-cause mortality — effects most consistently observed in middle-aged and older adults.

Why every 6 months

Morning serum cortisol, collected fasting before 9 am, is the standard clinical measurement of HPA axis basal output. The six-monthly Pulse+ draw is not designed to capture day-to-day or week-to-week cortisol variability — which requires salivary measurements, urinary free cortisol, or cortisol awakening response protocols — but rather to assess the chronic HPA axis state and its longitudinal trajectory. An individual whose morning cortisol is persistently at the upper end of the reference range across successive six-monthly measurements, and rising over time, is giving a different signal than one whose cortisol is mid-range and stable. This view contextualises the number: the trend across draws is more informative than any individual result in isolation.

What movement means

Standard laboratory reference ranges for morning serum cortisol in adults typically span 6–23 mcg/dL (166–635 nmol/L), with the understanding that values should be collected between 7 and 9 am in a fasting state. Values consistently at the upper end of this range warrant assessment of lifestyle factors — sleep quality, psychological stress load, visceral adiposity — and in clinical settings, consideration of formal HPA axis evaluation. Values below the lower end of the reference range may indicate adrenal insufficiency and warrant clinical review. The reference range describes the distribution in a population sample; it does not define the level associated with optimal health outcomes.

In the protocol