Generalized resistance to thyroid hormone is a rare condition; affected individuals have elevated serum levels of free
thyroxine and free
triiodothyronine with inappropriately normal or slightly elevated levels of
thyrotropin, yet are generally clinically euthyroid. However, responsiveness to
thyroid hormone varies from tissue to tissue, and some patients may benefit from treatment with exogenous
hormone. We have described the case of a patient with this disorder who initially had a mildly elevated serum
thyrotropin level and was clinically euthyroid but in whom symptomatic
autoimmune hypothyroidism subsequently developed. The serum free
thyroxine level, although diminished from its previously elevated value, remained within the normal range. The patient required substantial doses of
levothyroxine to return basal and stimulated TSH to their prior levels. Criteria for the treatment of adults with this disorder have not been firmly established. This case suggests that one indication for
thyroid hormone supplementation may be the presence of high-titer serum antithyroid
antibodies in patients who initially have mildly elevated
thyrotropin values; they could be at increased risk for progression to overt
hypothyroidism.