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Levothyroxine in Euthyroid Autoimmune Thyroiditis and Type 1 Diabetes: A Randomized, Controlled Trial

Division of Pediatric Endocrinology and Diabetes (B.K., J.A., A.R., K.M.D., E.H.), University Children’s Hospital Ulm, D-89075 Ulm, Germany; Institute of Biometrics (R.M.) and Division of Endocrinology (B.O.B.), Clinic for Internal Medicine I, University of Ulm, D-89081 Ulm, Germany; University Children’s Hospital Erlangen (I.K.), D-91054 Erlangen, Germany; Children’s Hospital Heidenheim (W.E.), D-89505 Heidenheim, Germany; Children’s Hospital Datteln (T.W.), D-45711 Datteln, Germany; University Children’s Hospital Tübingen (R.H., A.N.), D-72076 Tübingen, Germany; Children’s Hospital Chemnitz (A.K.), D-09009 Chemnitz, Germany; Department of Nuclear Medicine (A.S.), University of Würzburg, D-97080 Würzburg, Germany; and Division of Endocrinology and Diabetes (W.K.), RWTH Aachen University, D-52074 Aachen, Germany

Address all correspondence and requests for reprints to: Beate Karges, M.D., Division of Pediatric Endocrinology and Diabetes, University Children’s Hospital, University of Ulm, Eythstrasse 24, D-89075 Ulm, Germany. E-mail: beate.karges{at}uniklinik-ulm.de.

Context: Patients with type 1 diabetes (T1D) have an increased risk of autoimmune thyroiditis (AIT).

Objective: Our objective was to determine whether levothyroxine (L-T₄) treatment prevents the clinical manifestation of AIT in euthyroid subjects with T1D.

Design and Setting: We conducted a prospective, randomized, open, controlled clinical trial at six tertiary care centers for pediatric endocrinology and diabetes.

Patients: Of 611 children and adolescents with T1D, 89 individuals (14.5%) were identified with positive thyroid peroxidase antibodies (TPOAb), thyroglobulin antibodies (TgAb), or both. Of these, 30 patients (age, 13.3 ± 2.1 yr) met the inclusion criteria and were randomized to receive L-T₄ (n = 16 patients) or no treatment (n = 14 patients).

Intervention: L-T₄ (1.3 µg/kg daily) was given for 24 months in the treatment group, followed by an additional observation period of 6 months in both groups.

Main Outcome Measures: Thyroid gland volume (as determined by ultrasound), serum levels of TSH, thyroid hormones, TPOAb, and TgAb were assessed every 6 months for 30 months.

Results: Mean thyroid volume decreased in the treatment group after 24 months (–0.60 SD score) and increased in the observation group (+ 1.11 SD score; P = 0.0218). Serum thyrotropin, free T₄, TPOAb, and TgAb levels were not significantly different in both groups during the entire study period. Hypothyroidism developed in three individuals treated with L-T₄ and in four untreated patients (conversion rate, 9.3% per year).

Conclusions: In this study in euthyroid patients with AIT and T1D, L-T₄ treatment reduced thyroid volume but had no effect on thyroid function and serum autoantibody levels.