Cushing's Syndrome Explained

Cushing's syndrome is what happens when the body is exposed to too much cortisol over a long period. Cortisol is a vital stress hormone, but a sustained excess affects many systems and produces a recognisable pattern of changes. Diagnosis can be involved, because confirming excess cortisol and finding its source take several careful steps.

What Cushing's syndrome is

Cortisol is made by the adrenal glands, two small glands that sit above the kidneys. Its release is controlled by a chain of signals: the hypothalamus and the pituitary gland in the brain release hormones, including adrenocorticotropic hormone (ACTH), that tell the adrenals how much cortisol to produce. This system works as a feedback loop, so that rising cortisol normally signals the brain to ease off. Cortisol follows a daily rhythm, highest in the morning and lowest at night, and helps regulate blood sugar, blood pressure, the immune system, and the body's response to stress.

In Cushing's syndrome, cortisol stays too high for too long. This disrupts the normal rhythm and the body's balance, leading to the syndrome's characteristic features. The most common overall cause is taking certain medicines that act like cortisol; when the excess comes from inside the body, the condition arising from a pituitary tumour is specifically called Cushing's disease. Because cortisol touches so many systems, prolonged excess can affect metabolism, the skin, muscle, bone, mood, and more.

Common signs and symptoms

The features develop gradually and may include:

• Weight gain, especially around the abdomen and the upper back
• A rounder, fuller face
• Thin, fragile skin that bruises easily and heals slowly
• Wide purple or reddish stretch marks
• Muscle weakness, particularly in the upper arms and thighs
• Raised blood pressure and raised blood sugar
• Thinning bones over time
• Mood changes, irritability, or difficulty concentrating
• Tiredness and changes in sleep
• In women, irregular periods and increased facial or body hair

No single feature confirms the syndrome, and many of these changes are common in the general population. Clinicians often look for a combination of features and how they have evolved over time, sometimes comparing older and recent photographs to gauge gradual change.

What causes it

The most common cause overall is long-term use of glucocorticoid medicines, which are used for many conditions such as inflammatory and autoimmune diseases and act like cortisol in the body. This is sometimes called exogenous Cushing's syndrome because the cortisol-like effect comes from outside the body.

When the excess is produced internally, causes include a small benign tumour of the pituitary gland that drives the adrenals to overproduce (Cushing's disease), a tumour of an adrenal gland itself, or, less commonly, a tumour elsewhere in the body that produces ACTH. Identifying which of these applies — and whether ACTH is driving the process or not — is a central part of the diagnostic process and guides treatment.

How it is diagnosed

Diagnosis usually proceeds in two stages: first confirming that cortisol is genuinely in excess, then locating the source. Because cortisol varies through the day and with stress, clinicians use specific tests rather than a single random measurement. These may include:

• Late-night salivary cortisol — checking whether the normal night-time drop is lost.
• 24-hour urinary free cortisol — measuring cortisol output over a full day.
• A dexamethasone suppression test — assessing whether cortisol falls as expected after a dose of a cortisol-like medicine.
• ACTH measurement and imaging — to help locate the source once excess cortisol is confirmed.

The table below summarises, in illustrative terms only, how these steps fit together; the actual interpretation depends on the individual and is made by a clinician, often a hormone specialist.

For background on the cortisol test itself, see the MedlinePlus source below and our blood tests and hormones sections. The opposite problem, too little cortisol, is covered in our guide to Addison's disease, and related endocrine topics appear in our conditions overview.

How it is generally managed

Management depends entirely on the cause and is directed by specialists. When a medicine is responsible, a clinician may review whether it can be adjusted, which must never be done without medical guidance because stopping a glucocorticoid abruptly can be harmful. When an internal tumour is the cause, approaches can include surgery to remove it, and sometimes other treatments aimed at reducing cortisol or addressing the source. After treatment, the body's own cortisol control may need time and monitoring to recover. General treatment principles are outlined in our treatments section. This page is educational and does not provide personalised advice.

Complications and when to seek care

Sustained excess cortisol can contribute to high blood pressure, raised blood sugar, weakened bone and a higher chance of fracture — linking it to osteoporosis — muscle weakness, mood changes, and a greater susceptibility to infection. Because these effects build over time, recognising and addressing the underlying cause matters. Anyone taking long-term glucocorticoid medicine should follow their clinician's guidance closely and never stop suddenly. New severe headaches, vision changes, marked muscle weakness, or signs of infection warrant prompt medical attention.

Living with Cushing's syndrome

Living with the condition often involves working closely with a specialist team during diagnosis, treatment, and recovery. General health measures — balanced nutrition, gentle activity as advised, and attention to mood and sleep — can support wellbeing alongside medical care. Recovery after treatment can take time, and follow-up tests help a clinician track how cortisol balance and symptoms are settling. Because each cause and recovery path is individual, ongoing professional guidance is the most reliable source of advice.