Cortisol: What it does, how it's regulated, and why it matters

Cortisol is a steroid hormone produced and released by your adrenal glands. It belongs to a class of hormones called glucocorticoids and influences many systems in the body. While cortisol is widely known for its role in the stress response, it also helps regulate metabolism, inflammation, blood pressure and the sleep–wake cycle. Your body continuously monitors cortisol to keep levels within a healthy range; both excess and deficiency can cause health problems.

How cortisol affects the body

Cortisol acts on nearly every organ system. Key effects include:

• Stress response: During stress, cortisol is released (often following a surge of adrenaline) to help maintain alertness. It raises blood sugar by prompting the liver to release glucose so your body has immediate energy available.
• Metabolism and blood sugar regulation: Cortisol influences how your body uses glucose. It reduces insulin secretion and increases glucagon, shifting the balance to raise blood sugar when needed. It also affects glucose handling in fat, liver and muscle tissue.
• Inflammation and immune function: Short bursts of cortisol limit inflammation and can temporarily strengthen immune responses. However, chronically elevated cortisol can blunt immune function and paradoxically increase inflammation over time.
• Blood pressure: Cortisol helps modulate blood pressure. Persistently high cortisol may contribute to hypertension; conversely, very low cortisol can lead to low blood pressure.
• Sleep–wake cycle: Cortisol follows a diurnal rhythm for most people: levels are typically lowest in the evening and rise to a peak in the early morning, helping you wake and become alert. Disruptions to this pattern can affect sleep and daytime energy.

How the body controls cortisol

Cortisol production is regulated by the hypothalamic–pituitary–adrenal (HPA) axis:

• 1. Low blood cortisol prompts the hypothalamus to release corticotropin-releasing hormone (CRH).
• 2. CRH signals the pituitary gland to secrete adrenocorticotropic hormone (ACTH).
• 3. ACTH stimulates the adrenal glands to produce and release cortisol.

Healthy cortisol control depends on the coordinated function of the hypothalamus, pituitary and adrenal glands.

What causes high cortisol?

Long-term high cortisol (hypercortisolism) most commonly results from Cushing syndrome. Causes include:

• Prolonged use of corticosteroid medications (for example, prednisone or dexamethasone)
• ACTH-secreting tumors—often in the pituitary gland
• Adrenal tumors that produce excess cortisol

Symptoms of high cortisol (Cushing syndrome)

Signs can be varied and may include:

• Weight gain, especially in the face and abdomen
• Fatty deposits between the shoulders (buffalo hump)
• Wide purple stretch marks on the abdomen
• Weakness in upper arms and thighs
• Elevated blood sugar (which can progress to type 2 diabetes)
• High blood pressure
• Excessive hair growth in women (hirsutism)
• Reduced bone density and increased fracture risk

What causes low cortisol?

Low cortisol (hypocortisolism) is referred to as adrenal insufficiency and can be:

• Primary adrenal insufficiency (Addison's disease): often caused by an autoimmune attack on the adrenal glands, or less commonly by infection or hemorrhage of the glands.
• Secondary adrenal insufficiency: results from inadequate ACTH production by the pituitary (because of pituitary disease or abrupt withdrawal of long-term corticosteroids), which reduces adrenal cortisol output.

Symptoms of low cortisol (adrenal insufficiency)

Common symptoms include:

• Persistent fatigue
• Unintentional weight loss and poor appetite
• Low blood pressure (which may cause lightheadedness)
• General weakness and sometimes abdominal pain or nausea

When to see a healthcare provider

Contact a clinician if you have signs suggesting Cushing syndrome or adrenal insufficiency, or if stress-related symptoms are persistent and interfere with daily life. Seek urgent care if you experience severe weakness, fainting, severe abdominal pain, confusion, or symptoms of adrenal crisis. A healthcare provider can order tests to measure cortisol and related hormones and recommend appropriate treatment.

How can I lower cortisol?

If a medical condition like Cushing syndrome is causing high cortisol, specific medical or surgical treatments are required. For many people, lifestyle changes help lower or normalize cortisol levels and reduce stress:

• Prioritize quality sleep: chronic sleep deprivation or shift work can elevate cortisol.
• Stay physically active: regular exercise improves stress resilience and sleep.
• Practice relaxation techniques: deep breathing exercises, meditation and progressive muscle relaxation activate the parasympathetic ("rest and digest") system.
• Nurture social connections: supportive relationships reduce chronic stress.
• Include enjoyable activities and laughter: positive emotions release endorphins and counter stress hormones.
• Manage ongoing stressors: time management, boundary-setting and professional support (therapy or counseling) are often effective.