From the Guidelines
A normal basal cortisol level typically ranges between 5-25 micrograms per deciliter (mcg/dL) or 138-690 nanomoles per liter (nmol/L) when measured in the morning (around 8 AM). This range reflects the natural peak in cortisol production that occurs early in the day as part of the body's circadian rhythm, with individuals with normal adrenal function producing between 5 and 10 mg of cortisol per m2 of body surface area per day 1. Cortisol levels are normally highest in the morning and gradually decrease throughout the day, reaching their lowest point around midnight. This pattern is important for normal physiological functioning, as cortisol helps regulate metabolism, immune response, and stress reactions.
Key Points to Consider
- When interpreting basal cortisol results, timing of the sample is crucial since levels vary significantly throughout the day.
- Values below the normal range may suggest adrenal insufficiency, while consistently elevated levels might indicate conditions like Cushing's syndrome or chronic stress.
- If cortisol testing is needed, patients should follow any specific instructions regarding timing, medication use, and fasting requirements to ensure accurate results.
- It's also important to note that absolute adrenal insufficiency in children is defined by a basal cortisol <18 μg/dL and a peak adrenocorticotropic hormone (ACTH)-stimulated cortisol concentration <18 μg/dL 1.
Clinical Implications
- Accurate diagnosis and treatment of adrenal insufficiency or other conditions affecting cortisol levels are crucial to prevent morbidity and mortality.
- Patients with suspected adrenal insufficiency or other cortisol-related disorders should be referred to an endocrinologist for further evaluation and management.
- Hydrocortisone replacement therapy may be necessary for patients with absolute adrenal insufficiency or adrenal-pituitary axis failure and catecholamine-resistant shock 1.
From the Research
Normal Basal Cortisol Levels
- The normal basal cortisol level is not explicitly stated in the provided studies, but we can look at the cortisol levels mentioned in the context of Cushing's syndrome and adrenal insufficiency to understand the range of normal cortisol levels.
- In the study 2, a morning serum cortisol level of 13 μg/dL after 1 mg oral dexamethasone suppression is considered elevated, suggesting that normal morning cortisol levels are typically lower than this.
- In the study 3, a morning serum cortisol level of 0.20 μg/dL is considered low, indicating adrenal insufficiency.
- The study 4 discusses the utility of salivary cortisol measurements in Cushing's syndrome and adrenal insufficiency, but does not provide a specific range for normal basal cortisol levels.
Cortisol Levels in Different Conditions
- Cushing's syndrome: elevated cortisol levels, often above 13 μg/dL after dexamethasone suppression 2
- Adrenal insufficiency: low cortisol levels, often below 6.2 μg/dL 3
- Normal individuals: cortisol levels typically follow a circadian rhythm, with higher levels in the morning and lower levels at night 4