Several diseases can cause high cortisol levels, ranging from tumors on the pituitary or adrenal glands to certain cancers elsewhere in the body. The umbrella term for excess cortisol is Cushing’s syndrome, which affects roughly 7 to 15 people per million each year in the United States. But high cortisol can also result from long-term steroid medications, rare genetic conditions, and even chronic alcohol use.
Cushing’s Disease: Pituitary Tumors
Cushing’s disease is the single most common endogenous (meaning inside the body) cause of high cortisol. It happens when a benign tumor grows on the pituitary gland, a pea-sized structure at the base of the brain. This tumor produces excess ACTH, a signaling hormone that tells the adrenal glands to ramp up cortisol production. Because both adrenal glands respond to the signal, cortisol output rises well beyond what the body needs.
Cushing’s disease is progressive, meaning it worsens over time if left untreated. The term is often confused with Cushing’s syndrome, but the distinction is straightforward: Cushing’s syndrome refers to any condition that causes excess cortisol, while Cushing’s disease specifically means a pituitary tumor is to blame.
Adrenal Tumors
Tumors on the adrenal glands themselves can produce cortisol independently, ignoring the normal hormonal signals that would otherwise keep production in check. These are called cortisol-producing adenomas when benign, or adrenal carcinomas when cancerous. Either way, the tumor’s internal signaling is stuck in the “on” position. Mutations in genes that regulate a key enzyme pathway cause cells to continuously produce cortisol regardless of whether the body actually needs it.
Because these tumors operate autonomously, standard blood tests may show low ACTH (since the pituitary gland has stopped sending its signal) alongside high cortisol. This pattern helps doctors distinguish adrenal tumors from pituitary-driven Cushing’s disease, where ACTH is elevated.
Ectopic ACTH Syndrome
In about 5 to 10 percent of endogenous Cushing’s syndrome cases, a tumor somewhere outside the pituitary gland produces ACTH. This is called ectopic ACTH syndrome, and the most common culprits are small-cell lung cancer and neuroendocrine tumors of the lungs, thymus, or pancreas. Less frequently, thyroid medullary carcinoma, pheochromocytoma (an adrenal tumor that primarily affects adrenaline but can also secrete ACTH), gastrinoma, and prostate carcinoma are responsible.
The cortisol elevation in ectopic ACTH syndrome can be severe and rapid. In aggressive cancers like small-cell lung carcinoma, symptoms of high cortisol may appear suddenly alongside other cancer-related symptoms. In slower-growing tumors like bronchial carcinoids, the cortisol excess can develop gradually and be harder to trace back to its source. In one documented case, it took 22 months from the onset of symptoms to identify and remove a well-differentiated lung neuroendocrine tumor. Cortisol levels dropped within an hour of surgery.
Long-Term Steroid Medications
The most common cause of Cushing’s syndrome overall is not a disease at all. It is the prolonged use of corticosteroid medications like prednisone, dexamethasone, or hydrocortisone. These drugs are prescribed for conditions like asthma, rheumatoid arthritis, lupus, and inflammatory bowel disease. When taken at doses higher than what the body would naturally produce (roughly equivalent to more than 30 mg of hydrocortisone per day) for more than two to three weeks, they can push cortisol activity to levels that cause Cushing’s symptoms.
Nearly every form of corticosteroid delivery can do this. Oral pills are the most obvious source, but inhaled steroids, topical creams, and joint injections can all be absorbed into the bloodstream in sufficient quantities. Longer-acting formulations like dexamethasone and betamethasone carry a higher risk than shorter-acting ones like hydrocortisone or prednisolone. Herbal supplements contaminated with undisclosed glucocorticoids have also been documented as a hidden source.
The tricky part is that stopping these medications abruptly is dangerous. Prolonged steroid use suppresses the body’s own cortisol production, so the adrenal glands need time to wake back up. Tapering off slowly under medical guidance is essential.
Genetic Conditions
A handful of rare inherited disorders cause the adrenal glands to overproduce cortisol from a young age. The best studied is Carney complex, a dominantly inherited condition that causes tumors in multiple organs, including the adrenal glands. More than 60 percent of Carney complex cases involve mutations in a gene called PRKAR1A, which normally acts as a brake on cortisol production. When that gene is inactivated, the adrenal glands develop small nodules that churn out cortisol without the usual regulatory controls.
Other genetic mutations linked to hereditary cortisol excess include changes in PDE11A, PDE8B, PRKACA, and ARMC5. These are all components of the same cellular signaling chain. When any one of them malfunctions, the end result is the same: the adrenal cortex overexpresses the enzyme responsible for the final step of cortisol production, and cortisol levels climb.
Conditions That Mimic High Cortisol
Some conditions raise cortisol high enough to cause physical changes and abnormal lab results, yet no tumor or genetic mutation is involved. These are sometimes called “non-neoplastic hypercortisolism” or, in older terminology, pseudo-Cushing’s states.
Chronic heavy alcohol use is the most recognized trigger. Alcohol acutely stimulates cortisol secretion, and people with active alcohol use disorder have measurably higher cortisol output than controls. In severe cases, the physical signs are indistinguishable from true Cushing’s syndrome: facial rounding, plethora (redness), truncal obesity, fat accumulation at the base of the neck and between the shoulders, and wide purple stretch marks. These features can resolve after sustained abstinence, which is one way to tell the difference.
Certain psychiatric conditions also activate the cortisol axis. Depression, mania, and schizophrenia can all produce lab results that overlap with Cushing’s syndrome, making diagnosis more complicated. In these cases, treating the underlying psychiatric condition typically normalizes cortisol over time.
How High Cortisol Affects the Body
Regardless of the underlying cause, the physical effects of sustained high cortisol follow a recognizable pattern. Weight gain concentrates around the midsection and face while the arms and legs stay thin or lose muscle. A round, full face and a fatty hump between the shoulders are characteristic. The skin becomes fragile and bruises easily, and wide purple stretch marks appear on the abdomen, breasts, hips, and underarms. Muscles weaken, particularly in the thighs and upper arms, making it hard to climb stairs or lift objects overhead.
These changes develop gradually in most endogenous causes, often over months or years. Because symptoms like weight gain and fatigue are common in many conditions, Cushing’s syndrome is frequently underdiagnosed or diagnosed late.
How High Cortisol Is Confirmed
Diagnosing the cause of high cortisol typically starts with three screening tests. A late-night salivary cortisol test checks whether cortisol drops at bedtime the way it should. In healthy people, salivary cortisol falls below 145 ng/dL by late evening. A value above that threshold raises suspicion. A 24-hour urine collection measures total cortisol output over a full day, with results above the lab’s normal range considered abnormal. The third option is the overnight dexamethasone suppression test: you take a low dose of dexamethasone at bedtime, and your blood cortisol is measured the next morning. In a healthy person, the medication suppresses cortisol below 1.8 μg/dL. Failure to suppress suggests an autonomous cortisol source.
Once excess cortisol is confirmed, additional testing determines whether the source is ACTH-dependent (pituitary tumor or ectopic ACTH) or ACTH-independent (adrenal tumor or genetic adrenal disease). ACTH blood levels, imaging scans, and sometimes specialized sampling procedures help pinpoint the exact cause so treatment can be targeted appropriately.