Cushing’s disease is a hormonal disorder caused by a small, usually noncancerous tumor in the pituitary gland, a pea-sized gland at the base of the brain. The tumor produces too much of a signaling hormone that tells the adrenal glands (which sit on top of your kidneys) to pump out cortisol, the body’s main stress hormone. Over time, that excess cortisol changes how your body stores fat, handles blood sugar, maintains bone density, and even how you feel emotionally. Cushing’s disease is rare, affecting roughly 2 to 5 people per million each year, and it strikes women about four times more often than men.
Cushing’s Disease vs. Cushing’s Syndrome
These two terms are easy to confuse. Cushing’s syndrome is the broader category: any condition where cortisol stays too high for too long, regardless of the cause. Cushing’s disease is one specific cause of that syndrome, specifically the pituitary tumor version. Other causes of Cushing’s syndrome include long-term use of steroid medications like prednisone (the most common cause overall), tumors in the adrenal glands themselves, or rarely, tumors elsewhere in the body that produce the same signaling hormone the pituitary does.
When doctors say “Cushing’s disease,” they always mean a pituitary tumor is driving the problem. When they say “Cushing’s syndrome,” they may not yet know the cause, or the cause may be something other than a pituitary tumor.
How a Pituitary Tumor Raises Cortisol
Your pituitary gland normally releases a hormone called ACTH in carefully controlled amounts. ACTH travels through the bloodstream to the adrenal glands, telling them how much cortisol to make. In Cushing’s disease, a tumor (called a corticotroph adenoma) on the pituitary ignores the body’s normal feedback signals and keeps producing ACTH even when cortisol levels are already high. The adrenal glands respond by making more and more cortisol, and the excess accumulates over weeks, months, or years.
Most of these tumors are microadenomas, meaning they’re smaller than 10 millimeters. That’s part of what makes the condition tricky to detect. Even a tiny cluster of cells can flood the body with enough signaling hormone to cause widespread symptoms.
What Cushing’s Disease Looks Like
The symptoms develop gradually, which is one reason diagnosis often takes years. Many of the early signs, like weight gain, fatigue, and mood changes, overlap with far more common conditions. But as cortisol levels stay elevated, a distinctive pattern emerges:
- Fat redistribution. Fat accumulates in the face (creating a round “moon face”), around the base of the neck, and between the shoulders (sometimes called a buffalo hump), while the arms and legs may actually become thinner as muscle wastes away.
- Skin changes. Wide, purple or reddish stretch marks appear on the abdomen, breasts, hips, and underarms. These are different from the pale, thin stretch marks that come with ordinary weight gain. The skin also bruises easily and heals slowly.
- Metabolic problems. High cortisol pushes blood sugar up, often leading to type 2 diabetes or prediabetes. Blood pressure rises. Bones thin, increasing fracture risk, sometimes significantly.
- Emotional and cognitive changes. Anxiety, depression, irritability, difficulty concentrating, and sleep disruption are common. Some people describe feeling like a different person.
- Other signs. Women may notice irregular periods and excess facial or body hair. Both men and women can experience decreased sex drive. Muscle weakness, particularly in the thighs, makes it hard to climb stairs or stand up from a chair.
How It’s Diagnosed
Diagnosis happens in two stages. First, doctors confirm that cortisol is genuinely too high. Then they figure out why.
Confirming High Cortisol
The most common screening tests include a 24-hour urine collection to measure cortisol output over a full day, a late-night saliva test (cortisol should be at its lowest before bed), and a suppression test where you take a small steroid pill at night and have blood drawn the next morning. In a healthy person, the pill signals the brain to dial back cortisol production. In someone with Cushing’s, cortisol stays stubbornly high. Levels six to seven times the upper limit of normal on urine testing are generally considered diagnostic.
Finding the Source
Once excess cortisol is confirmed, blood tests check ACTH levels. If ACTH is elevated, the problem is coming from either the pituitary or somewhere else in the body that’s producing ACTH inappropriately. An MRI of the pituitary gland is the next step. Higher-strength MRI scanners (3T) detect these small tumors about 82% of the time, compared to roughly 74% for standard 1.5T machines. When the MRI doesn’t show a clear tumor, doctors may use a specialized test called inferior petrosal sinus sampling, which measures ACTH levels in the veins draining directly from the pituitary to confirm that’s where the excess is coming from.
Treatment Options
Surgery is the first-line treatment for nearly all cases of Cushing’s disease. The goal is to remove the pituitary tumor while preserving the rest of the gland.
Pituitary Surgery
The operation is performed through the nose and sinuses, avoiding any external incisions or the need to open the skull. Remission rates after this surgery range from 68% to 95%, depending on the tumor’s size and the surgeon’s experience. A large 20-year study found an overall remission rate of 83%. When the first surgery is successful, the long-term remission rate reaches about 95%. When it isn’t, a second surgery brings the remission rate to only about 36%, which is why getting to an experienced pituitary surgeon matters.
Recovery after surgery typically means a few days in the hospital. One important thing to know: after a successful operation, your body has been relying on excess cortisol for so long that your normal hormone-producing system is suppressed. You’ll need to take replacement cortisol for months, sometimes a year or more, while your pituitary and adrenal glands slowly wake back up. About 10% of patients develop permanent hormonal deficiencies that require ongoing replacement.
When Surgery Isn’t Enough
If the tumor can’t be fully removed, or if it comes back, several options remain. Medications can either block cortisol production in the adrenal glands or target the pituitary tumor itself. Radiation therapy aimed at the pituitary can shrink residual tumor tissue, though it works slowly over months to years. In rare, severe cases, removing both adrenal glands eliminates cortisol production entirely, but this means lifelong hormone replacement.
Recurrence After Successful Surgery
Even when surgery achieves remission, Cushing’s disease can come back. Studies report recurrence rates of 5% to 50% within 10 years, a wide range that depends on tumor characteristics. Research published in The Lancet found that the genetic makeup and size of the tumor matter significantly. Certain genetic variants in the tumor were linked to a 37% recurrence rate over 10 years, while small tumors without those variants recurred only about 15% of the time. Larger tumors without the variant had the highest recurrence rate, around 45%.
This means long-term follow-up is essential after treatment. Regular cortisol testing, typically yearly for at least a decade, helps catch a recurrence early, when it’s easier to treat.
Living With the Effects of Excess Cortisol
Even after cortisol levels return to normal, recovery isn’t instant. The physical changes, weight redistribution, muscle weakness, thinning bones, take months to years to reverse, and some effects like stretch marks may be permanent. Many people describe the recovery period as unexpectedly difficult. Fatigue, joint pain, and emotional ups and downs are common as the body adjusts to normal cortisol levels after being flooded for so long.
The metabolic complications, including high blood sugar, high blood pressure, and bone loss, need their own management during and after treatment. Some of these improve significantly once cortisol normalizes. Others, particularly bone density loss, may need targeted treatment to rebuild what was lost. The psychological effects can linger too; depression and cognitive difficulties sometimes persist for a year or more after remission, gradually improving as the brain adapts to normal hormone levels.