Wednesday, September 25, 2013

Another "dopamine-producing" pheo

Some days ago, I got a call from a physician asking me for suggestions on how to proceed with a “dopamine-producing” pheo. The patient was an elderly man with labile blood pressure and varying heart rate. Pheo was suspected. Urine dopamine levels were >5000 mcg/24 hours (normal reference range: 60-450). But was it a pheo?

I usually get 1 or 2 calls on potential "dopamine-producing" pheo every year. True dopamine-producing pheos are extremely rare and do not cause clear symptoms. These tumors are usually localized outside the adrenal glands and may present as metastatic tumors. They are usually clinically silent until they grow very big and causing abdominal discomfort. Specifically they do not cause hypertension per se. Only about half of the patients have high dopamine only and the other half have high dopamine and high epinephrine or norepinephrine as well.

In any given situation, the most common cause of very high urine or plasma dopamine is the medication Carbidopa-Levodopa (Sinemet) for Parkinson disease. These patients usually have every high dopamine but normal or slightly elevated epinephrine or norepinephrine. Levodopa is presumably converted into dopamine which is then detected by the catecholamine measurement. Parkinson disease and related conditions such as multiple system atrophy often cause sympathetic instability in the forms of fluctuating blood pressure and heart rate, orthostatic hypotension, and syncope, all of which resemble pheo symptoms.

I therefore asked the physician if the patient had Parkinson disease. He was reasonably surprised and told me the patient did have Parkinson. I then asked if the patient took Sinemet. He checked the medication list but Sinemet was not on the list. I was not swayed. Many patients think Parkinson is a disease of old age and Sinemet some kind of food supplement so they do not tell their doctor they are taking it. Luckily the patient was still in the clinic. The physician told me he would ask the patient about Sinemet and call me back. He didn't call me back. I assumed the patient was taking Sinemet, as all of the patients I had been asked about are.

Dr. Pheo



P.S. I have not written about pheo for 7 months for various reasons. My job is more demanding, to be sure. Also, there has not been a major advancement in the pheo field in the last 7 months, in my opinion.