Cushing’s syndrome – Diagnostics – Overview of Information and Clinical Research

Diagnosing Cushing’s syndrome requires careful testing because its symptoms can resemble other conditions. The journey to diagnosis often begins when someone notices unusual changes in their body—unexplained weight gain, a rounder face, or persistent fatigue—and decides to seek medical help. Understanding what tests and procedures are involved can help ease the uncertainty that comes with this process.

Introduction: When to Seek Diagnostic Testing

If you notice changes in your body that don’t seem to have an obvious explanation, it may be time to talk to your doctor about Cushing’s syndrome. This condition happens when your body has too much of a hormone called cortisol, which is often referred to as the “stress hormone.” While cortisol is essential for many body functions—helping to regulate blood pressure, control blood sugar, and respond to stress—having too much of it for a long time can cause serious health problems.^[1]

You should consider seeking medical attention if you experience a combination of symptoms that persist over time. These might include rapid weight gain, especially around your midsection, face, and upper back; skin that bruises easily or develops purple stretch marks; muscle weakness; high blood pressure; or changes in mood such as increased irritability or depression. Women may notice irregular or absent periods, while men might experience erectile problems.^[2]

Cushing’s syndrome is rare, affecting only about 40 to 70 people out of every million each year. Because of its rarity and because its symptoms can be similar to other more common conditions, it can be challenging to diagnose.^[3] This is why seeing a specialist called an endocrinologist—a doctor who focuses on hormone-related conditions—is important. An endocrinologist has the expertise to distinguish Cushing’s syndrome from other conditions that might cause similar symptoms.^[2]

Anyone can develop Cushing’s syndrome, but it is much more common in women than in men, affecting about three times as many women. It typically appears in adults between the ages of 25 and 50, though children and teenagers can also develop it.^[2] People who take steroid medications for conditions like asthma, rheumatoid arthritis, or other autoimmune diseases for extended periods are at higher risk, as these medications can cause the same effects as too much natural cortisol.^[5]

⚠️ Important

If you are taking steroid medications and notice symptoms of Cushing’s syndrome, do not stop taking your medication suddenly. Stopping abruptly can make you very unwell. Always talk to your doctor first about the best way to manage your medication.^[8]

Diagnostic Methods for Identifying Cushing’s Syndrome

Diagnosing Cushing’s syndrome can be a lengthy and complex process. The first step is often a thorough physical examination. Your doctor will look for visible signs such as a rounded face (sometimes called “moon face”), a fatty hump between your shoulders (called a “buffalo hump”), thin skin with stretch marks particularly on your belly and thighs, and easy bruising.^[10] However, because these physical changes develop gradually and can be caused by other conditions, further testing is always necessary to confirm the diagnosis.

Reviewing Your Medications

The most common cause of Cushing’s syndrome is taking high doses of steroid medicines—such as hydrocortisone or prednisolone—for a long time. If this applies to you, your healthcare provider will carefully review all your medications, including pills, injections, creams, and inhalers. If steroid medication is identified as the cause, you may not need additional diagnostic tests.^[10]

Laboratory Tests to Measure Cortisol Levels

When Cushing’s syndrome is caused by your body producing too much cortisol naturally, several types of laboratory tests are used to measure hormone levels and confirm the diagnosis. These tests need to show that your body is consistently making too much cortisol over time.^[11]

One common test is the 24-hour urine collection. For this test, you will be asked to collect all of your urine over a full 24-hour period. The sample is then analyzed in a laboratory to measure the amount of cortisol your body is releasing. This test is helpful because it captures cortisol production throughout an entire day, rather than just at a single moment.^[10]

Blood tests are also used to measure cortisol and another hormone called ACTH (adrenocorticotropic hormone). ACTH is produced by the pituitary gland in your brain and tells your adrenal glands to release cortisol. By measuring both cortisol and ACTH levels, doctors can begin to understand where the problem is coming from—whether it’s the pituitary gland, the adrenal glands, or somewhere else in the body.^[10]

A saliva test is another useful diagnostic tool. Normally, cortisol levels rise and fall throughout the day, with the highest levels in the morning and the lowest levels at night. In people with Cushing’s syndrome, cortisol levels remain high even at night when they should be low. By collecting a small sample of saliva late at night, doctors can check whether your cortisol levels are inappropriately elevated.^[10]

Stimulation and Suppression Tests

Your healthcare provider might recommend additional specialized tests that measure how your body responds to certain medications. One such test is the dexamethasone suppression test. In this test, you are given a medication called dexamethasone at night, and your blood is drawn the next morning. In people without Cushing’s syndrome, dexamethasone causes cortisol levels to drop. In people with Cushing’s syndrome, cortisol levels remain high despite the medication. This helps confirm that the body is producing too much cortisol.^[10]

Imaging Tests to Locate Tumors

Once blood and urine tests confirm that cortisol levels are too high, imaging tests are used to find out what is causing the excess cortisol. The most common imaging tests are CT (computed tomography) scans and MRI (magnetic resonance imaging) scans. These scans take detailed pictures of the inside of your body and can help doctors see if there are any tumors or growths on your pituitary gland or adrenal glands.^[10]

Most often, Cushing’s syndrome is caused by a small, non-cancerous tumor on the pituitary gland. When the tumor is located in the pituitary gland, the condition is specifically called Cushing’s disease. Cushing’s disease accounts for more than 70% of all Cushing’s syndrome cases in adults.^[2] In other cases, the problem may be a tumor on one or both adrenal glands, or rarely, a tumor elsewhere in the body—such as in the lungs or pancreas—that is producing hormones that stimulate cortisol production.^[6]

Distinguishing Cushing’s Syndrome from Other Conditions

Because many symptoms of Cushing’s syndrome—such as weight gain, high blood pressure, and fatigue—are common to other conditions, it can take time to arrive at the correct diagnosis. Doctors must carefully rule out other illnesses that might cause similar symptoms. This is why the diagnostic process often involves multiple tests over weeks or even months.^[10] The combination of physical examination, laboratory tests, and imaging helps doctors build a complete picture and distinguish Cushing’s syndrome from other health problems.

⚠️ Important

Cushing’s syndrome can be difficult to diagnose because its symptoms develop gradually and overlap with many other conditions. If your initial tests are not conclusive, your doctor may ask you to repeat certain tests or try different ones. This does not mean the testing is failing—it simply reflects the complexity of diagnosing this rare condition. Be patient and continue working closely with your healthcare team.^[10]

Diagnostics for Clinical Trial Qualification

When patients are being considered for enrollment in clinical trials for Cushing’s syndrome, specific diagnostic tests and criteria are used to ensure that participants have confirmed disease and are suitable candidates for the study. Clinical trials are research studies that test new treatments or medications, and they have strict eligibility requirements to ensure the safety of participants and the accuracy of results.

Before a patient can be enrolled in a clinical trial, the diagnosis of Cushing’s syndrome must be firmly established through the standard diagnostic tests described earlier—such as 24-hour urine cortisol measurements, blood tests for cortisol and ACTH, saliva tests, and dexamethasone suppression tests. Imaging studies, including MRI or CT scans, are typically required to identify the source of excess cortisol production, whether it is a pituitary tumor, adrenal tumor, or another cause.^[12]

Clinical trials may also require baseline measurements of how Cushing’s syndrome is affecting your body. This can include tests to assess complications such as high blood pressure, high blood sugar or diabetes, bone density measurements to check for osteoporosis (weakening of the bones), and evaluations of muscle strength and function. These baseline assessments help researchers understand the severity of the disease and measure whether the treatment being studied is effective.^[12]

Some trials may have additional specific criteria. For example, trials testing medications for Cushing’s disease (the type caused by a pituitary tumor) may require confirmation through specialized tests that distinguish pituitary-caused disease from other types. Other trials might exclude patients who have already undergone certain treatments, such as surgery or radiation, or they may specifically seek patients whose disease has returned after initial treatment.^[12]

If you are interested in participating in a clinical trial, your endocrinologist will work with you to determine whether you meet the specific eligibility criteria. They will review your diagnostic test results, medical history, and current health status. Participating in a clinical trial can provide access to new treatments that are not yet widely available, but it is important to understand the requirements and potential risks involved. Your healthcare team will help you make an informed decision about whether a clinical trial is right for you.^[12]

Prognosis and Survival Rate

Prognosis

The outlook for people with Cushing’s syndrome depends on several factors, including how quickly the condition is diagnosed, how severe the symptoms are, and whether treatment is successful. When Cushing’s syndrome is left untreated, it can lead to serious and potentially life-threatening complications. These include infections, blood clots in the lungs and legs, heart attacks, severe bone loss leading to fractures, type 2 diabetes, high blood pressure, and depression. Without treatment, Cushing’s syndrome can result in death.^[2]

However, the sooner treatment begins, the better the chances for recovery. With appropriate treatment—whether through surgery, medication, or other therapies—many of the symptoms and complications of Cushing’s syndrome can improve or even resolve over time.^[1] The recovery process varies greatly from person to person. Factors that affect recovery include how long you had Cushing’s syndrome before it was diagnosed, how severe your symptoms and complications were, and your age. Younger patients tend to recover more quickly than older patients.^[25]

It is important to understand that recovery can take time—often six months to a year or longer. Physical symptoms such as muscle weakness and weight gain may take many months to improve, while emotional symptoms like irritability and mood swings often improve sooner. Memory and concentration problems may take longer to fully resolve.^[25] Even after successful treatment, some patients may experience lower quality of life compared to people of the same age and gender without the disease, though this varies widely among individuals.^[25]

Survival Rate

Specific survival rate statistics for Cushing’s syndrome are not widely reported in the available sources. However, it is well established that untreated or poorly controlled Cushing’s syndrome significantly increases the risk of death due to complications such as cardiovascular disease, infections, and metabolic problems.^[2] Early diagnosis and effective treatment are critical to reducing these risks and improving long-term outcomes. With proper medical care and ongoing monitoring, many people with Cushing’s syndrome can lead active lives and experience significant improvement in their health and well-being.^[1]

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