Cortisol: the hormone released when stress or low glucose

Cortisol is a steroid hormone (derived from cholesterol) produced by the adrenal glands, located above the kidneys. These glands respond to stimulation from another hormone called adrenocorticotropin (ACTH), produced by the pituitary gland, which promotes cortisol synthesis.

Cortisol is primarily released in response to stress or low blood glucose levels. Its main functions include increasing blood glucose levels by promoting gluconeogenesis, suppressing the immune system, and facilitating the metabolism of proteins, fatty acids, and carbohydrates. Additionally, cortisol is involved in other functions such as water and electrolyte homeostasis and blood pressure regulation.

High cortisol levels can result from the prolonged use of certain corticosteroid medications. However, abruptly stopping these medications may cause cortisol levels to drop below normal.

Certain diseases can also lead to elevated cortisol levels. If these levels remain excessively high and untreated, the patient may develop serious conditions. The most common disorders affecting cortisol levels include:

• Cushing's syndrome: a condition that occurs when the body has too much cortisol for an extended period
• Addison’s disease (primary adrenal insufficiency): a condition where the adrenal glands are damaged and do not produce enough cortisol
• Secondary adrenal insufficiency: a condition where the adrenal glands do not produce enough cortisol because the pituitary gland is not functioning properly

Cushing’s syndrome results from high cortisol levels in the blood. It can be categorized as:

• ACTH-dependent: caused by a pituitary or ectopic tumor (in other parts of the body, such as the lungs or pancreas) that produces large amounts of ACTH, overstimulating cortisol synthesis
• ACTH-independent: characterized by normal ACTH levels, often caused by an adrenal tumor producing excess cortisol or by other conditions like adrenal nodular hyperplasia. It can also result from the administration of glucocorticoids

Symptoms of Cushing’s syndrome include:

• Weight gain
• Thin arms and legs
• Round face
• Increased fat around the base of the neck or between the shoulders
• Easy bruising
• Purple stretch marks on the abdomen, breasts, hips, and underarms
• Muscle weakness
• Addison’s disease

Addison’s disease occurs due to abnormally low cortisol levels in the blood, caused by adrenal gland dysfunction that reduces cortisol production. Causes of Addison’s disease include:

• Autoimmune diseases that damage or impair adrenal gland function
• Certain infections, such as tuberculosis (TB) or human immunodeficiency virus (HIV)

Symptoms of Addison’s disease include:

• Persistent fatigue
• Muscle weakness
• Loss of appetite
• Weight loss
• Abdominal pain

Secondary adrenal insufficiency occurs when the adrenal glands do not produce enough cortisol due to issues with the pituitary gland. Common causes include:

• Autoimmune diseases affecting ACTH secretion in the pituitary gland
• Other pituitary disorders
• Traumatic brain injury

The cortisol test measures cortisol levels in the blood. While this test can indicate abnormal cortisol levels, it cannot identify the underlying cause. Additional tests are required for a conclusive diagnosis.

High cortisol levels are often a sign of Cushing’s syndrome, while, low cortisol levels are commonly associated with Addison’s disease or secondary adrenal insufficiency. However, other factors can also elevate cortisol levels, such as:

• Stress
• Pregnancy
• Exercise
• Severe illness
• Extreme temperatures (hot or cold)
• Certain thyroid disorders
• Obesity
• Medications, such as contraceptives