Thyroid function tests during the early phase of subacute thyroiditis.

Six patients with subacute thyroditis were followed with serial measurements of T4, FT4, TSH and RAI uptake. Five of the six underwent TRH stimulation early in the course of their illness. All six patients had elevated or high normal values for T4 and FT4 at the time of their clinical presentation (mean = 13.8 microgram per 100 ml and 3.9 ng per 100 ml, respectively). RAI uptakes were 1% or less in all six. TRH testing revealed a suppressed TSH response (mean deltaTSH less than0.1 muU/ml) in all five patients tested, suggesting hyperthyroidism. After initial studies were performed, five patients were treated with L-triiodothyronine (L-T3) and one with aspirin. All patients improved over a two to four week period of time, no relapses being noted.