Interleukin-2 (IL-2) is frequently incorporated in
antineoplastic therapy: While the effect of
interferon on the thyroid has been extensively studied the impact of other
cytokines on thyroid function is less well understood. We monitored the thyroid function in six patients who received
IL-2 in combination with
tumor necrosis factor-alpha (TNF) or
alpha-Interferon (alpha IFN).
Hyperthyroxinemia with suppressed TSH developed within the first four weeks of
IL-2 administration; during this phase, there was no
technetium or
iodine uptake by the thyroid gland. During the following few weeks, serum
thyroxine decreased and serum TSH rose, consistent with the development of
primary hypothyroidism; during this phase, thyroidal
isotope incorporation was normal. All hypothyroid patients received
thyroxine replacement
therapy upon documentation of
hypothyroidism; in several cases
thyroxine was successfully discontinued after 2-3 months. None of the patients had detectable antithyroidal
antibodies and none experienced thyroid-related
pain, although two patients developed thyroid enlargement. We conclude that
IL-2 administration is associated with the development of transient, subacute, painless
thyroiditis. The frequency and severity of this complication requires further elucidation through systematic, prospective study.