What is Adrenal Hypercortisolism (AHC)?

Adrenal hypercortisolism (AHC) means that a tumor (nodule) in one or both adrenal glands makes more of the hormone cortisol than the body needs, on its own and outside the normal control of the pituitary gland. It is also called primary or ACTH-independent hypercortisolism. On your reports you may have seen the older names MACS (mild autonomous cortisol secretion) or subclinical Cushing syndrome; these describe the milder forms of the same disease. AHC is a spectrum that runs from mild, through moderate, to severe. Severe AHC is the classic, overt adrenal Cushing syndrome. For a benign cortisol-producing adrenal tumor, surgery (most often the Mini Back Scope Adrenalectomy; MBSA) cures the cortisol excess in nearly all patients.

AHC is common. It is the most frequent hormone excess found in adrenal tumors, including the adrenal nodules discovered by chance on a scan done for another reason (adrenal incidentalomas). It is also greatly underdiagnosed: most patients do not look like the textbook picture of Cushing syndrome, and the right test is often not ordered.

Not having the classic Cushing look does not mean the cortisol is harmless. Even mild AHC raises the risk of high blood pressure, diabetes, osteoporosis and fractures, and cardiovascular disease such as heart attack and stroke. The damage adds up over years. "Mild" describes a lab value, not the effect on your health.

Cushing Syndrome and High Cortisol: the Background

In 1932, the neurosurgeon Harvey Cushing described 12 patients (2 of his own and 10 from the medical literature) with central body obesity, glucose intolerance (i.e. diabetes), hypertension (high blood pressure), excess hair growth, osteoporosis, kidney stones, menstrual irregularity, and emotional lability. It is now known that these features characterize Cushing syndrome, which is the result of long-term exposure to too much cortisol. The most common cause overall is steroid medication (such as prednisone) taken for other conditions. The pages in this section are about cortisol that the body itself makes in excess.

Cortisol is a powerful steroid hormone, and excess cortisol has detrimental effects on many cells throughout the body. Keep in mind that overt Cushing syndrome is rare, with only a few new cases per million people per year. However, milder overproduction of cortisol by an adrenal tumor (mild and moderate AHC) is very common. Conversely, obesity, heavy alcohol use, depression and poorly controlled diabetes can raise cortisol and cause some of these symptoms in the absence of any tumor, which is one reason careful testing matters.

Cortisol production by the adrenal glands is normally under the control of the pituitary, a small endocrine gland at the base of the brain, behind the bridge of the nose and close to the nerves to the eyes. The pituitary makes ACTH (adrenocorticotropic hormone), the signal that tells the adrenals to release cortisol. Overproduction of cortisol can therefore be caused by a tumor in the pituitary or by a tumor within the adrenal glands themselves. When a pituitary tumor secretes too much ACTH, it causes the otherwise normal adrenal glands to produce too much cortisol. This type of Cushing syndrome is termed Cushing's disease. That name applies only to the pituitary form and should never be used for an adrenal tumor. In Cushing's disease, ACTH is normal or high when it should be suppressed.

Note from the Carling Adrenal Center: Adrenal surgery is all we do. We do not perform surgery on the brain or pituitary gland. However, if you have Cushing's disease due to an ACTH-producing pituitary tumor, you can always contact us, and we will direct you to a high-volume surgeon who does pituitary surgery (usually a neurosurgeon). You want an expert pituitary surgeon to do your operation. Like adrenal surgery, pituitary surgery is tricky and requires significant expertise and experience.

When an adrenal gland develops a tumor, the tumor may produce excess amounts of the hormone normally made by those cells. If the adrenal tumor is composed of cortisol-producing cells, excess cortisol will be produced. Under these conditions, the normal pituitary senses the excess cortisol and makes less ACTH to slow the adrenals down. A low ACTH, usually together with a low DHEA-S (another adrenal hormone that depends on ACTH), therefore points to the adrenal gland as the source. In this manner, physicians can distinguish whether excess cortisol is the result of a pituitary tumor or an adrenal tumor.

Even rarer is when excess ACTH is produced somewhere other than the pituitary (ectopic ACTH). This is uncommon, but certain tumors, for example in the lung, thymus or pancreas, can produce ACTH. In this situation, patients develop Cushing syndrome in the same way as if the ACTH were coming from the pituitary.

What are the causes of high cortisol and Cushing Syndrome?

Cortisol excess made by the body is divided into a) ACTH-dependent Cushing syndrome (i.e. due to overproduction of ACTH, most often by a pituitary tumor. Only rarely is adrenal surgery necessary in these cases) b) ACTH-independent cortisol excess, which is adrenal hypercortisolism (AHC). For a benign adrenal tumor, adrenal surgery cures the cortisol excess in nearly all patients
  • ACTH-dependent (the adrenal glands are driven by too much ACTH)
    • Pituitary tumors (Cushing's disease)
    • Ectopic ACTH from tumors outside the pituitary (for example in the lung, thymus or pancreas)
  • ACTH-independent: adrenal hypercortisolism (AHC)
    • Benign adrenal tumors (adenoma), by far the most common
    • Tumors in both adrenal glands, including primary bilateral macronodular adrenal hyperplasia (PBMAH), now also called bilateral macronodular adrenal cortical disease
    • Malignant adrenal tumors (adrenocortical carcinoma), which are rare
    Note from the Carling Adrenal Center: Among patients with overt Cushing syndrome, the pituitary form is the more common one. Once mild and moderate AHC (formerly MACS or subclinical Cushing syndrome) are counted, however, the adrenal gland is by far the most common source of cortisol excess. Adrenalectomy is the only cure for AHC, and it is usually done as a scope operation. Some patients have more than one hormone problem: an adrenal tumor can make both cortisol and aldosterone, which is why patients with primary aldosteronism should also be tested for cortisol excess. Read more about Adrenal Surgery here.

    Next, read about the symptoms of AHC, how it is diagnosed, and adrenalectomy for AHC.

    Last updated October 2026.

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