Dr Nick Fuller
Leading Obesity Expert at the University of Sydney and founder of Interval Weight Loss.
Cushing's syndrome happens when your body has too much cortisol, a hormone that helps regulate metabolism, immune function, and stress response. While cortisol is essential, too much of it can throw everything off balance. This condition can develop due to prolonged corticosteroid use or from your body producing excessive cortisol on its own.
Cushing's syndrome is rare, with 1.8 to 4.5 new cases per million people each year. But overall, more people are living with it—around 57 to 79 per million—because it often takes a while to diagnose. Symptoms can include weight gain, skin changes, mood swings, and more serious issues like high blood pressure and diabetes.
Let's break down what causes it, the signs to watch for, and how it affects different groups.
Excess cortisol can come from internal factors like tumours or external sources like medication. Here are the most common causes:
A non-cancerous tumour in the pituitary gland, called a pituitary adenoma, can push your adrenal glands into overdrive, making way too much cortisol. This is known as Cushing disease, and it’s behind about 80% of Cushing’s syndrome cases that aren’t caused by medication. The tricky part? Symptoms creep in slowly, so it’s not always easy to catch early.
Sometimes, tumours outside the pituitary gland, like in the lungs or pancreas, start making ACTH, the hormone that tells your adrenal glands to pump out cortisol. These ectopic tumours can be either harmless or cancerous, but they often bring on symptoms fast. Think severe muscle weakness, sudden weight loss, and a whole lot of trouble for your body.
The adrenal glands can develop tumours that produce too much cortisol. These tumours may be benign (adrenal adenomas) or cancerous (adrenal carcinomas). Unlike pituitary-related cases, adrenal tumours often cause one adrenal gland to enlarge, which can be spotted on imaging tests.
Taking corticosteroid meds like prednisone for a long time can mimic Cushing’s syndrome. These drugs help with conditions like autoimmune diseases, asthma, and chronic inflammation, but in high doses over time, they can mess with your body’s natural cortisol balance and cause similar symptoms.
Excess cortisol affects nearly every part of the body. Below are 12 signs to look out for.
Unexplained weight gain, especially around the abdomen, face, and upper back, is one of the hallmark signs. Unlike regular weight gain, this pattern occurs due to cortisol’s role in fat distribution.
Often called a moon face, this puffiness happens as cortisol redistributes fat to the face. The skin may also appear flushed or red.
Cortisol suppresses the immune system, making it harder for the body to repair wounds, cuts, or bruises. Even minor injuries can take longer than usual to heal.
Cushing's syndrome can trigger hormonal acne, particularly on the face, chest, and back. The skin may also feel oilier than usual.
High cortisol levels break down proteins in the skin, making it thinner and more fragile. This can lead to easy bruising and increased visibility of veins.
Dark purple or reddish stretch marks, usually on the abdomen, thighs, breasts, or arms, are common. They result from rapid weight gain and skin fragility.
Cortisol breaks down muscle tissue, leading to noticeable weakness, particularly in the arms and legs. Simple tasks like climbing stairs may feel exhausting.
Cortisol affects brain function, which can lead to mood swings, irritability, anxiety, and even depression. In some cases, it can contribute to cognitive issues like memory problems.
Excess facial and body hair growth (hirsutism) can occur, particularly in women. This happens due to cortisol’s interaction with androgen (male hormone) levels.
High cortisol can interfere with estrogen production, leading to irregular or missing periods. This can also affect fertility.
Men with Cushing's syndrome may experience a drop in testosterone levels, leading to reduced sex drive and potential fertility problems.
Cortisol increases blood pressure and glucose levels, raising the risk of hypertension, type 2 diabetes, and cardiovascular disease.
Cushing’s syndrome is rare in kids, making up only about 10% of new cases each year. Unlike adults, children often experience severe growth stunting because cortisol interferes with bone development. Instead of gradual weight gain, kids with Cushing’s tend to put on weight quickly in their torso while their arms and legs stay thin. Delayed puberty is another common sign, which can make diagnosis even trickier.
Since the symptoms can look like more common issues, such as obesity or hormonal imbalances, Cushing’s is often diagnosed late. Catching it early is key to preventing long-term effects on height, bone health, and metabolism.
Though more common in women, Cushing’s syndrome can have a big impact on men, especially when it comes to testosterone levels. Signs include reduced muscle mass, low libido, and erectile dysfunction, since excess cortisol lowers testosterone. Men with Cushing’s are also more prone to insulin resistance and metabolic issues, increasing the risk of type 2 diabetes.
Unlike women, men with Cushing’s are less likely to have visible hormonal symptoms like acne or excessive hair growth, making it harder to spot. If left untreated, it can lead to serious issues like osteoporosis, heart disease, and long-term infertility.
Cushing’s syndrome is more common in women, especially between 25 and 40. Some of the most noticeable signs include irregular or missing periods, excessive facial hair (hirsutism), and acne—thanks to elevated androgen levels. These hormonal changes can make it harder to conceive, and if left untreated, Cushing’s can increase the risk of infertility and pregnancy complications.
Since the symptoms are similar to conditions like polycystic ovary syndrome (PCOS), many women are misdiagnosed or dismissed. Spotting the mix of metabolic and hormonal changes is key to getting the right diagnosis and treatment.
Untreated Cushing's syndrome can lead to serious health issues, such as:
Cortisol weakens bones by reducing calcium absorption, increasing fracture risk, particularly in the spine, hips, and ribs.
Around 80% of people with Cushing's syndrome develop high blood pressure, increasing their risk of heart attacks and strokes.
Cortisol raises blood sugar levels, which can lead to insulin resistance and an increased risk of diabetes.
Muscle loss, especially in the thighs and upper arms, can make daily activities difficult.
A weakened immune system increases the likelihood of recurrent infections, including skin infections and pneumonia.
Anxiety, depression, mood swings, and even severe mental health disorders like psychosis can develop with prolonged high cortisol levels.
In addition to thinning and stretch marks, some people experience excess oil production and increased bruising.
Fat accumulation in the abdomen, back, and face is common, leading to metabolic complications.
Both men and women may struggle with fertility problems due to hormonal imbalances.
Cortisol disrupts the sleep cycle, leading to insomnia or poor sleep quality.
Cushing's syndrome is more than just weight gain and a round face—it’s a serious hormonal disorder that can impact almost every system in the body. If you notice multiple symptoms, talk to a doctor for testing and early treatment. Managing cortisol levels can help prevent long-term complications and improve overall well-being.
Dr Nick Fuller is the founder of Interval Weight Loss and is a leading obesity expert at the University of Sydney with a Ph.D. in Obesity Treatment. Dr Fuller is also the author of three best-selling books and his work been published in top ranked journals in the medical field, including JAMA, Lancet and American Journal of Clinical Nutrition.