Background: Delayed thyroid-stimulating hormone (TSH) recovery during treatment of Graves disease is caused by long-term excessive thyroid hormone, which results in down-regulation of pituitary thyrotropic cells. However, it is unknown whether delayed TSH recovery exists after levothyroxine (LT4) dose adjustment in patients with differentiated thyroid cancer (DTC) who are taking a suppressive dose of LT4.
Methods: We retrospectively reviewed 97 DTC patients who had a reduced LT4 dose while receiving excessive LT4 for TSH suppression. TSH levels at baseline (point 1), 6 months (point 2), and 12-18 months (point 3) after LT4 dose adjustment were compared with each other. A delayed TSH recovery group whose TSH levels exceeded target TSH levels (according to recent guidelines) between points 2 and 3 was identified.
Results: In patients with LT4 reduction, the median TSH level at point 3 was significantly higher than that at point 2 [0.17 vs 0.09 μIU/ml; P<0.001). The delayed TSH recovery group (44.3%, 43 of 97 patients) showed increased body weight during follow-up (60.8462.73 kg; P=0.01), although TSH levels remained in the target range. A lower LT4 dose per body weight (LT4 dose/weight) after reduction [HR (95% CI), 0.01 (0.000.54); P=0.03], greater changes in the LT4 dose/weight [1.10 (1.001.22); P=0.04], and higher BMI before surgery [1.19 (1.031.38); P=0.01] predicted the occurrence of delayed TSH recovery.
Conclusions: Delayed TSH recovery was commonly observed after LT4 dose adjustment was performed as recommended by dynamic risk stratification. Six months may not be enough time to evaluate real thyroid hormone status by TSH levels.
20 - 23 May 2017
European Society of Endocrinology