(See also Overview of the Adrenal Glands.)
A pheochromocytoma is a tumor that usually originates from the adrenal glands’ chromaffin cells, causing overproduction of catecholamines, powerful hormones that induce high blood pressure and other symptoms.
High blood pressure is the most important symptom, but a fast and pounding pulse, excessive sweating, light-headedness when standing, rapid breathing, severe headaches, and many other symptoms may also occur.
Doctors measure the blood levels of catecholamines or products created when catecholamines are broken down by the body and use imaging tests to try to find the tumor.
Usually, the best treatment is to remove the pheochromocytoma.
Most pheochromocytomas grow within the adrenal glands. About 10% grow in chromaffin cells outside the adrenal glands. Less than 10% of pheochromocytomas that grow within the adrenal glands are cancerous, but this percentage is higher for those outside the adrenal glands. Pheochromocytomas may occur in men or women at any age, but they are most common in people between the ages of 20 and 40.
Some people who develop pheochromocytomas have a rare inherited condition called multiple endocrine neoplasia that makes them prone to tumors in the thyroid, parathyroid, and adrenal glands. Pheochromocytomas may also develop in people who have von Hippel–Lindau disease and in those who have neurofibromatosis (von Recklinghausen disease) or a number of other genetic diseases. It is likely that nearly 50% of people who have pheocromocytomas have a genetic or familial disease such as these.
Pheochromocytomas may be quite small. However, even a small pheochromocytoma can produce large amounts of potent catecholamines. Catecholamines are hormones such as adrenaline (epinephrine), norepinephrine, and dopamine, which tend to greatly increase blood pressure and heart rate and cause other symptoms usually associated with life-threatening situations.
The most prominent sign of a pheochromocytoma is high blood pressure, which may be very severe. However, only about 1 in 1000 people with high blood pressure has a pheochromocytoma. Symptoms include
When these symptoms appear suddenly and forcefully, they can feel like a panic attack.
In half of affected people, symptoms come and go, sometimes triggered by pressure on the tumor, massage, drugs (especially anesthetics and beta-blocking drugs), emotional trauma, and, on rare occasions, the simple act of urination. However, many people may have these symptoms as manifestations of an anxiety state, not a glandular disorder.
Doctors may not suspect a pheochromocytoma, because almost half of the people have no symptoms other than persistent high blood pressure. However, when high blood pressure occurs in a young person, comes and goes, or accompanies other symptoms of pheochromocytoma, doctors may request certain laboratory tests. For example, the level of certain catecholamines or products created when these catecholamines are broken down may be measured in blood or urine samples. Because of high blood pressure and other symptoms, doctors may prescribe a beta-blocker before knowing that the cause is a pheochromocytoma. Beta-blockers can make high blood pressure worse in people with pheochromocytoma. This paradoxical reaction often makes the diagnosis of pheochromocytoma clear.
If the level of catecholamines is high, computed tomography (CT) or magnetic resonance imaging (MRI) can help locate the pheochromocytoma. A test using injected radioactive chemicals that tend to accumulate in pheochromocytomas can also be useful. A scan is then done to see where the radioactive chemicals are.
Genetic tests may be done, particularly if doctors suspect a genetic disease.
Usually the best treatment is to remove the pheochromocytoma. Surgery is often delayed, however, until doctors can bring the tumor’s secretion of catecholamines under control with drugs, because having high levels of catecholamines can be dangerous during surgery. Phenoxybenzamine or a similar drug is generally given to stop hormone action. Once this step is accomplished, a beta-blocker can safely be given to further control symptoms.
If the pheochromocytoma is cancerous and has spread, chemotherapy rarely cures the tumor. Newer chemotherapy drugs such as temozolomide and sunitinib seem to help slow the tumor’s growth. Treatment with a radioisotope known as metaiodobenzylguanidine (MIBG) that targets the tumor tissue can also be highly effective. The dangerous effects of the excess catecholamines secreted by the tumor can almost always be blocked by continuing to take phenoxybenzamine or a similar drug and beta-blockers.