Subclinical hypothyroidism in the first years of life in patients with Down syndrome.

BACKGROUND

Subclinical hypothyroidism (SH), defined as mild thyroid-stimulating hormone (TSH) elevation with normal free thyroxine (FT4) levels and no symptoms, is common during the first few years of life in Down syndrome (DS) and can be self-limiting. Our objective was to confirm that SH is usually a transitory disorder and to identify the factors associated with spontaneous remission.

METHODS

We reviewed clinical histories of patients from the Catalan Down Syndrome Foundation (CDSF) with DS and SH diagnosed before 5 y of age. SH was defined as TSH 5.5-25 µU/ml (6 mo-4 y) or 4.13-25 µU/ml (4-7 y), with FT4 0.89-1.87 ng/dl (6 mo-4 y) or 0.96-1.86 ng/dl (4-7 y).

RESULTS

Fifty-three patients with SH were identified, with an average age of 2.4 ± 1.1 y, median (range) TSH at diagnosis 7.1 (4.2-23.9 µU/ml), and median (range) FT4 1.1 (0.9-1.7 ng/dl). SH resolved spontaneously in 39 cases (73.6%), with TSH at the most recent visit (mean age 6.7 ± 1.4 y) 3.9 (1.8-12.7 µU/ml). The rate of remission was significantly higher in patients without goiter (94.9 vs. 28.6%) and in those who were negative for antithyroid antibodies (89.7 vs. 42.9%).

CONCLUSION

SH in infants and preschool children with DS is usually a transitory disorder, with remission in >70% of cases. The absence of goiter and thyroid autoantibodies was associated with a greater rate of spontaneous remission in our study.