Cortisol, Serum (Morning Sample)

Cortisol is a vital hormone produced by the adrenal glands, two small glands that are located above the kidneys. It affects almost every organ and tissue in your body and plays various roles such as:

• Control the balance of water and electrolytes
• Reduce inflammation
• Support your immune system
• Handle stress (often called the “stress hormone”)
• Maintain blood pressure and blood sugar levels

Abnormal cortisol levels may suggest problems with the adrenal glands, pituitary gland, or even the presence of a tumor that produces cortisol.

High cortisol levels may occur in conditions like Cushing’s syndrome, tumors of the adrenal or pituitary glands, and in some cases, due to tumors outside these glands, which make ACTH (a hormone that triggers cortisol production). Cortisol can also increase because of long-term steroid medication use, emotional or physical stress, low blood sugar (hypoglycemia), depression, and an overactive thyroid (hyperthyroidism). On the other hand, low cortisol levels can be seen in Addison’s disease, poor function of the adrenal glands (called adrenal insufficiency), or problems in the body’s process of making cortisol.

Cortisol levels in the body are controlled by ACTH, a hormone made by the pituitary gland. The release of ACTH is triggered by another hormone called corticotropin-releasing hormone (CRH), which is produced by the hypothalamus. This process works in a daily cycle. Cortisol levels are highest in the early morning (around 6 a.m. to 8 a.m.) and lowest late at night (around 11 p.m.).

The Cortisol, Serum (Morning Sample) test is usually done early in the morning because cortisol levels are highest at that time. This helps get the most accurate results and gives a clear picture of how well the adrenal glands are working.  In people with Cushing’s syndrome, this rhythm is often disrupted, and cortisol levels may remain high even in the late evening. By measuring cortisol levels later in the day, doctors can distinguish between normal daily variation and the abnormal cortisol production seen in Cushing’s syndrome. However, these levels can also be affected by stress or other health conditions. Since cortisol follows the body’s daily (circadian) rhythm, your doctor may ask you to avoid vigorous exercise the day before the test, as it may affect the results.

Lab test results may vary across laboratories. Abnormal test results require an expert interpretation. Therefore, never try to self-medicate at home based solely on these results, and always consult a doctor for a proper understanding of the test results.