Objective: We aimed to determine the reproducibility of TSH testing in pediatric patients referred to pediatric endocrinologists and to identify the threshold TSH levels that would predict the presence of antithyroid autoantibodies and inform decisions by pediatric endocrinologists to initiate or continue treatment with levothyroxine.
Study design: We analyzed a retrospective case series of 325 children aged 1 to 18 years referred for hypothyroidism to the endocrinology clinic at a tertiary care children's hospital. The receiver operating characteristic area under curve (AUC) determined the ability of the initial TSH level to predict pediatric endocrinologists' treatment decisions, presence of thyroid autoantibodies, and reproducibility of elevated TSH on repeat testing.
Results: Of 325 patients, 191 were treated. The treated patients were more likely to have had a higher referral TSH, positive autoantibodies, and abnormal thyroid gland examination findings. An initial TSH of 5 had a specificity of only 14% for a repeat TSH of ≥5. An initial TSH level of 11 had a specificity of 90% for a repeat TSH of ≥11, with sensitivity of 90%. TSH was a relatively poor predictor (AUC, 0.711) of the presence of autoantibodies with optimal classification at TSH >8.8 mIU/L. It was better (AUC, 0.878) at predicting whether endocrinologists started or continued treatment with levothyroxine, with optimal classification at 8.2 mIU/L. TSH levels combined with antibody status and thyroid examination findings had the best ability to predict treatment (AUC, 0.930).
Conclusions: TSH levels slightly above the reference range should not prompt referral to pediatric endocrinologists unless another basis for clinical concern is present.
Keywords: autoantibodies; levothyroxine; receiver operating characteristic curve; subclinical hypothyroidism.
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