OBJECTIVETo investigate the changes in thyroglobulin antibodies (TgAb) and its influencing factors in differentiated thyroid cancer (DTC) patients with positive TgAb (>115 U/ml) after total thyroidectomy and radioiodine (¹³¹I) therapy.

METHODSWe collected the clinical data of 118 DTC patients with positive TgAb and analyzed their TgAb levels before surgery, before ¹³¹I therapy, and after ¹³¹I therapy with a median follow-up of 2.3 months and 5.2 months. Multiple linear regression (MLR) was applied to analyze the time of TgAb concentration decreased by more than 50% (T₅₀) and its influencing factors.

RESULTSCompared with the previous TgAb levels, TgAb decreased significantly 2.3 months and 5.2 months after surgery or after ¹³¹I therapy, respectively (both P=0.000). The proportions of patients with TgAb decreased by more than 50% in each stage were 28.6%,33.3%, and 37.2%,respectively. The negative conversion ratios were 23.4%,48.9%, and 62.8%,respectively. MLR showed that only the interval between surgery and ¹³¹I therapy was correlated with T₅₀ (B=1.125, P=0.000).

CONCLUSIONSThe TgAb levels in DTC patients remarkably decrease after surgery and after ¹³¹I therapy. The interval between surgery and ¹³¹I therapy remarkably influences the lowering speed of TgAb levels. Prompt application of ¹³¹I therapy after surgery helps to lower TgAb levels.