An adrenal adenoma is a common, non-cancerous growth that forms within the adrenal glands, the small, hormone-producing organs situated directly above the kidneys. These glands create hormones that regulate metabolism, blood pressure, and the body’s response to stress. An adenoma originates specifically from the outer layer, or cortex, of the adrenal gland. Because these growths rarely cause symptoms, they are most often discovered accidentally during imaging scans for unrelated health concerns, leading to the designation “adrenal incidentaloma”.
Defining Adrenal Adenomas and Their Types
Adrenal adenomas are the most frequent type of tumor found in the adrenal glands. These benign growths arise from the adrenal cortex, the region responsible for producing steroid hormones like cortisol and aldosterone. They typically present as well-defined, homogeneous masses and do not spread to other parts of the body.
The classification of an adrenal adenoma depends on its functional status—whether it produces excess hormones. The majority are non-functional, meaning they do not secrete excessive hormones and cause no symptoms. These non-functional tumors are most frequently discovered by chance on a computed tomography (CT) or magnetic resonance imaging (MRI) scan.
A smaller percentage are functional adenomas, actively secreting hormones beyond normal levels. The two most common forms involve the overproduction of either cortisol or aldosterone. This hormonal overactivity dictates the presence of symptoms and the need for treatment. Rarely, an adenoma may secrete sex hormones, such as androgens or estrogens, leading to distinct symptoms.
Recognizing Symptoms of Functional Adenomas
Functional tumors create specific symptom complexes due to excessive hormone production. Overproduction of the stress hormone cortisol can lead to Cushing’s syndrome. Symptoms include centralized weight gain around the torso, a round face, and muscle weakness, particularly in the limbs.
Excess cortisol also contributes to high blood pressure, elevated blood sugar levels, and characteristic purple stretch marks on the skin. Overproduction of aldosterone results in primary aldosteronism, also known as Conn’s syndrome. This excess causes resistant hypertension—high blood pressure difficult to control even with multiple medications.
The excessive aldosterone causes the body to retain sodium and excrete potassium, often resulting in low blood potassium levels. Low potassium can manifest as muscle weakness, fatigue, and muscle cramps.
How Adrenal Adenomas Are Diagnosed and Evaluated
Diagnosis employs a two-part strategy: imaging to characterize the physical mass and biochemical testing to determine its functional status. Imaging tests, typically CT or MRI scans, are used to assess the adenoma’s size and composition. A benign adenoma often appears homogeneous and may have a low density on a non-contrast CT scan.
Imaging also helps rule out malignancy, as tumors with features like a large size (greater than 4 cm) or irregular shape are viewed with higher suspicion. The second step is the hormonal workup, performed regardless of whether the patient has symptoms. This testing determines if the adenoma is functional, even if hormone production is subclinical.
Hormonal Testing
To screen for cortisol excess, an overnight 1-milligram dexamethasone suppression test is frequently used. This test determines if a small dose of medication suppresses cortisol production. For detecting aldosterone overproduction, the aldosterone-to-renin ratio in the blood is measured, especially in patients with hypertension or low potassium. These tests are necessary to understand the tumor’s biological activity, which guides the management plan.
Management and Treatment Options
Management depends on the adenoma’s size and functional status. For the majority of adenomas that are small, non-functional, and appear benign, the preferred course is active surveillance, or “watchful waiting.” This involves monitoring the tumor with repeat imaging scans, usually at six to twelve months, and periodic blood tests to confirm it is not becoming hormonally active.
If the adenoma is functional or large (greater than 4 centimeters), surgical removal, known as an adrenalectomy, is generally recommended. Surgery is the preferred treatment for hormonally active tumors because it resolves excess hormone production and associated symptoms, such as resistant hypertension. The procedure is often performed using minimally-invasive laparoscopic techniques.
If surgery is not possible, medical management is an option for functional tumors. Medications can block the effects of excess hormones, such as using spironolactone to counteract aldosterone in Conn’s syndrome. Patients managed medically require ongoing monitoring and potential adjustments to their drug regimen.