Cushing’s disease is a hormonal disorder caused by a small, usually noncancerous tumor on the pituitary gland that forces the body to produce far too much cortisol. It accounts for about 8 out of 10 cases of Cushing’s syndrome that aren’t caused by steroid medications, making it the most common endogenous form. The condition is rare, with an estimated global incidence of roughly 2 to 5 cases per million people per year.
How It Differs From Cushing’s Syndrome
Cushing’s syndrome is the broader term for any condition that results in prolonged, excessive cortisol. That can include long-term use of corticosteroid medications, tumors on the adrenal glands, or cancers elsewhere in the body that produce hormones. Cushing’s disease refers specifically to cases driven by a pituitary tumor. The distinction matters because the cause determines the treatment.
What Happens Inside the Body
The pituitary gland, a pea-sized structure at the base of the brain, normally produces a signaling hormone called ACTH that tells the adrenal glands (which sit on top of your kidneys) how much cortisol to make. In a healthy system, when cortisol levels get high enough, the pituitary receives that signal and dials back ACTH production. It’s a feedback loop that keeps cortisol in a normal range.
In Cushing’s disease, a pituitary tumor disrupts this loop. The tumor cells are resistant to the “stop producing” signal from cortisol. Several things go wrong inside these tumor cells: they break down cortisol into an inactive form more readily, and they lose the molecular machinery that would normally let cortisol shut off ACTH production. The result is that the tumor keeps pumping out ACTH regardless of how much cortisol is already circulating, and the adrenal glands keep responding by making more.
Recognizable Symptoms
Excess cortisol reshapes the body in distinctive ways. A rounded “moon face” is the most common visible sign, appearing in 81 to 90 percent of patients. About half develop fat deposits between the shoulders (sometimes called a buffalo hump) and across the upper back. Purple or reddish stretch marks wider than typical stretch marks show up in 44 to 50 percent of cases, often on the abdomen, thighs, or upper arms.
Beyond the physical changes you can see, chronically elevated cortisol causes a cascade of internal problems. It raises blood sugar, sometimes to the point of diabetes. It weakens bones, raises blood pressure, suppresses the immune system, and frequently triggers mood changes ranging from anxiety and irritability to depression. Many people gain weight primarily around the midsection while their arms and legs actually thin out from muscle wasting. Fatigue, easy bruising, and slow wound healing are common. Women may notice irregular periods or excess facial hair, and men may experience decreased fertility.
How It’s Diagnosed
Diagnosis typically starts with screening tests that measure cortisol output in different ways. A late-night saliva sample checks whether cortisol levels drop the way they should in the evening. A 24-hour urine collection measures total cortisol output over a full day. A third option involves taking a low dose of a synthetic steroid at bedtime and measuring cortisol the next morning to see if the body’s production appropriately suppresses. In healthy people, cortisol drops. In Cushing’s disease, it stays elevated.
Once excess cortisol is confirmed, the next step is figuring out the source. Blood tests measuring ACTH levels help distinguish pituitary-driven cases from adrenal tumors (which suppress ACTH rather than elevate it). An MRI of the pituitary gland is then used to look for the tumor, but these tumors are often tiny. MRI picks them up about 71 percent of the time for small tumors (microadenomas), meaning nearly 3 in 10 cases are missed on imaging. When MRI doesn’t show a clear tumor, doctors may use a more specialized procedure called inferior petrosal sinus sampling, which measures ACTH levels in the veins draining the pituitary to confirm whether the gland is the source. This test is invasive and correctly identifies which side of the pituitary the tumor is on only about 69 percent of the time.
Surgery as First-Line Treatment
The primary treatment is surgical removal of the pituitary tumor, performed through the nose and sinuses in a procedure called transsphenoidal surgery. The Endocrine Society recommends this as the first option for nearly all patients. In experienced hands, remission rates are strong: one large single-center study found that about 83 percent of patients achieved remission, including some who needed a second surgery shortly after the first. Recurrence does happen, though. In that same study, six patients experienced a return of the disease, on average about three years after surgery.
After successful surgery, your body needs time to restart its own cortisol production. The pituitary and adrenal glands have been suppressed by the tumor’s excess output, and they don’t bounce back immediately. Most patients need to take cortisol replacement medication for a period after surgery, with a median duration of about 6 months for Cushing’s disease patients, though some need it for much longer.
Medications When Surgery Isn’t Enough
If surgery doesn’t fully resolve the disease, or if a patient isn’t a good candidate for an operation, medications can help control cortisol levels. The main approaches work in different ways. Some drugs target the adrenal glands directly, blocking the enzymes that produce cortisol. Osilodrostat, approved by the FDA in 2020, falls into this category and can bring cortisol under control within about two weeks. Other medications, like pasireotide, target the pituitary tumor itself, reducing its ACTH output. Older drugs like ketoconazole and metyrapone have been used for years to lower cortisol, though they were never formally FDA-approved for this specific purpose.
These medications manage the disease but don’t cure it. They’re often used as a bridge to other treatments or as a long-term option for people who can’t undergo or have failed surgery. Radiation therapy directed at the pituitary is another option, though it takes months to years to reach full effect.
What Recovery Actually Looks Like
Recovery after successful treatment is slower than most patients expect. Endocrinologists estimate a median recovery time of about 12 months, but patients themselves report feeling fully recovered at closer to 18 months, with some taking several years. That gap between when doctors consider you recovered and when you feel recovered is significant and worth knowing about upfront.
The physical changes from excess cortisol don’t reverse overnight. Weight redistribution, muscle rebuilding, bone strengthening, and mood stabilization all happen gradually. Many patients describe a withdrawal-like period after cortisol normalizes, with fatigue, joint pain, and low mood that can feel worse before it gets better. Your body spent months or years adapted to abnormally high cortisol, and readjusting to normal levels is its own process.
Throughout recovery, monitoring for related health problems is important. High blood pressure, elevated blood sugar, weakened bones, mood disorders, and increased clotting risk all need to be tracked and managed alongside the primary disease. Vaccinations, particularly for influenza and pneumonia, are recommended because the immune system takes time to fully recover from prolonged cortisol exposure.