Dopamine, but not dobutamine or dopexamine,
inhibits thyrotropin secretion
(November 2004)
The background of the study. Patients with nonthyroidal
illness, particularly those in intensive-care units, may have low
serum thyrotropin (TSH) concentrations, which may be caused by drugs
given to increase cardiac output. The effects of three such drugs,
dopamine, dobutamine, and dopexamine, on TSH secretion were evaluated
in this study.
How the study was done. The study subjects were
30 men who underwent elective major abdominal surgery. One day after
surgery, the men were randomly assigned to receive dopamine, dobutamine,
or dopexamine for eight hours. The dose was increased gradually
at 10-minute intervals as needed to raise cardiac output by 35 percent,
and then maintained at this level. Cardiac output, oxygen delivery,
oxygen consumption, and serum TSH were measured at baseline and
repeatedly during the infusions, and 2 and 16 hours later.
The results of the study. During the infusions,
cardiac output increased by 36 to 38 percent, oxygen delivery by
31 to 34 percent, and oxygen consumption by 22 to 23 percent in
the three groups. The average final infusion rates were 5.0 µg/kg/min
for dopamine, 4.1 µg/kg/min for dobutamine, and 0.7 µg/kg/min
for dopexamine.
In the men given dopamine, the average serum TSH concentration
decreased from 1.1 mU/L to 0.3 mU/L in two hours. The mean values
were <0.3 mU/L during the rest of the infusion, and they were
similar to base line 2 and 16 hours after the infusion. There were
no changes in serum TSH concentrations in the men given dobutamine
or dopexamine.
The conclusions of the study. In postoperative
surgical patients, infusions of dobutamine and dopexamine have little
effect on TSH secretion, whereas a dose of dopamine that has a similar
cardiac effect inhibits TSH secretion.
The original article. Schilling T, Grundling M,
Strang CM, Moritz KU, Siegmund W, Hachenberg T. Effects of dopexamine,
dobutamine or dopamine on prolactin and thyreotropin serum concentrations
in high-risk surgical patients. Intensive Care Med 2004;30:1127-33.
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