Radiographic contrast agents have little
acute effect on pituitary–thyroid function
(November 2004)
The background of the study. Water-soluble radiographic
contrast agents contain large amounts of iodide, which can lead
to changes in thyroid function weeks later. This study evaluated
the acute effects of these agents on thyroid function in normal
subjects.
How the study was done. The study subjects were
22 patients who underwent elective coronary arteriography or computed
tomography, during which they received intravenous injections of
a water-soluble radiographic contrast agent. None had a history
of thyroid disease or was seriously ill, and all had normal serum
thyrotropin (TSH) and free thyroxine (T4) concentrations. These
hormones were measured twice before and daily for seven days after
contrast administration.
The results of the study. The total doses of iodide
administered were very high, ranging from 300 to 1121 mg/kg of body
weight. The patients’ serum free T4 concentrations did not
change, but their serum TSH concentrations increased slightly but
statistically significantly on days 3 and 4 (Table).
The mean maximal increase in serum TSH was 2.4 mU/L, and four patients
had values slightly above the normal range at some time.
The conclusions of the study. In patients with
normal thyroid function, intravenous administration of a radiographic
contrast agent has little effect on serum T4 concentrations, but
may cause a small transient increase in TSH secretion.
The original article. Gartner W, Weissel M. Do
iodine-containing contrast media induce clinically relevant changes
in thyroid function parameters of euthyroid patients within the
first week? Thyroid 2004;14:521-4.
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