Cortisol Blood Test Kit

Cortisol is a steroid hormone produced by the adrenal glands (small glands that sit on top of each kidney) in response to signals from the pituitary gland in the brain, which in turn receives signals from the hypothalamus. This regulatory system is called the hypothalamic-pituitary-adrenal (HPA) axis. Cortisol is often called the 'stress hormone' because its production increases in response to physical or psychological stress, but it actually has many essential functions in the body beyond the stress response. Cortisol helps regulate blood sugar by promoting gluconeogenesis (glucose production) in the liver; it helps control blood pressure; it has powerful anti-inflammatory and immunomodulatory effects; it influences mood and cognitive function; and it helps regulate the sleep-wake cycle. Cortisol follows a pronounced circadian rhythm—levels are highest in the early morning (typically peaking around 6-8am), which helps trigger waking and provides energy for the day ahead. Levels then gradually decline through the day, reaching their lowest point around midnight. This is why timing of collection is so critical for interpretation. A morning cortisol level that falls within the normal reference range generally indicates that the adrenal glands are capable of producing adequate cortisol. A very low morning cortisol (typically below 100 nmol/L) raises concern for adrenal insufficiency and warrants further investigation. A very high morning cortisol may suggest Cushing's syndrome (cortisol excess), though this also requires further testing to confirm. Conditions associated with abnormal cortisol include: Addison's disease (primary adrenal insufficiency) where the adrenal glands are damaged; secondary adrenal insufficiency where the pituitary fails to produce adequate ACTH; Cushing's syndrome caused by tumours, long-term steroid use, or other conditions causing excess cortisol; and chronic stress which can affect cortisol patterns. Women taking oestrogen-containing contraceptives or hormone replacement therapy typically show elevated total cortisol because oestrogen increases cortisol-binding globulin—in these cases, the measured cortisol is higher but the biologically active 'free' cortisol may be normal. Results outside the normal range may need a follow-up with your GP.