Adenomas of the adrenal gland are non-cancerous (benign) tumors on the adrenal gland. Most do not cause any signs or symptoms and rarely require treatment. However, some may become "active" or "functioning" which means they produce hormones, often in excess of what the adrenal glands typically produce. High levels of these hormones can lead to complications, including primary aldosteronism, Cushing's syndrome and other medical conditions. Functioning adrenal adenomas may be treated with surgery and/or medications.

The exact underlying cause of most adrenal adenomas is unknown. They sometimes occur in people with certain genetic syndromes such as multiple endocrine neoplasia, type 1 (MEN1) and familial adenomatous polyposis (FAP). In these cases, affected people usually have multiple adenomas and other characteristic features of the condition that are all caused by changes (mutations) in a gene. MEN1 is caused by mutations in the MEN1 gene, while FAP is caused by mutations in the APC gene.

The majority of adrenal adenomas are "nonfunctioning", which means they do not produce hormones and usually do not cause any symptoms. They are often found incidentally during imaging studies of the abdomen, in which case they are referred to as adrenal incidentalomas. However, some can become "functioning" or "active" and secrete excess hormones. Depending on the type of hormone released, adrenal tumors can cause a variety of conditions, including Cushing's syndrome, primary aldosteronism, or much less commonly, virilization.

Cushing's syndrome, also called hypercortisolism (having abnormally high levels of cortisol), is caused by adrenal adenomas that release excess levels of the hormone cortisol. Common symptoms of Cushing's syndrome can include upper body obesity; severe fatigue and muscle weakness; high blood pressure; backache; high blood sugar; easy bruising; and bluish-red stretch marks on the skin. Affected women may have increased growth of facial and body hair, and menstrual periods may become irregular or stop completely. Mild hypercortisolism without any obvious symptoms, called subclinical Cushing's syndrome, is common in people with an adrenal incidentaloma, although glucose intolerance and hypertension may be present in these cases.

Primary aldosteronism (also called Conn syndrome) is a condition in which the adrenal gland produces too much of the hormone aldosterone. This hormone is responsible for balancing the levels of sodium and potassium in the blood. Symptoms of this condition may include high blood pressure, fatigue, headache, muscle weakness, numbness and paralysis that comes and goes.

Benign cortisol-secreting adenomas can also produce small amounts of androgens (steroid hormones, such as testosterone), although androgen levels in the blood are usually not elevated. Excess amounts of androgens can cause an increase in masculine characteristics (virilization) such as increased facial and body hair (hirsutism); deepening of the voice; increased muscularity; and other characteristics.

The best treatment options for adenomas of the adrenal gland depend on many factors, including whether or not the adenoma is "functional" (releasing hormones). People with adrenal adenomas that are not releasing hormones usually do not require any immediate treatment; however, they may need to follow up with a healthcare provider regularly to determine if the adenoma has grown and to make sure that it does not start producing hormones.

Functional adrenal adenomas are typically treated with surgery. Removal of the affected adrenal gland usually resolves other medical conditions that may be present as a result of elevated adrenal hormones (i.e. primary aldosteronism, Cushing's syndrome). In some cases, functional adrenal adenomas can be treated with medications that block the function or lower the levels of the overproduced hormone.

The long-term outlook for people with adenomas of the adrenal gland is usually excellent. Although adrenal adenomas that are functional (releasing hormones) can cause other medical problems such as primary aldosteronism and Cushing's syndrome, these conditions usually respond well to treatment with medications and/or surgery. Nonfunctional adrenal adenomas typically do not cause any problems and rarely require treatment.

In addition to a complete physical exam and medical history, the following imaging tests are usually necessary to diagnose an adenoma of the adrenal gland: computed tomography (CT scan), magnetic resonance imaging (MRI scan), and/or positron emission tomography (PET scan). Some people may also need a biopsy of the tumor to confirm the diagnosis. Laboratory tests that evaluate the levels of certain hormones in the blood or urine can be used to determine if the adrenal adenoma is functional or nonfunctional.

Most adrenal adenomas are not inherited. They usually occur sporadically in people with no family history of tumors. However, in rare cases, they can occur in people with certain genetic syndromes such as multiple endocrine neoplasia, type 1 (MEN1) and familial adenomatous polyposis (FAP). Both of these conditions are inherited in an autosomal dominant manner.