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.
