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.
t he prevalence of medical conditions in individuals withDown syndrome (DS) is greater than in the general population, which has negative implications for their quality of life and life expectancy (1). Among these medical problems, thyroid pathology is a primary area of concern. Both hyper-and hypothyroidism occur more often in patients with DS (1-3), the latter disorder occurring six times more frequently than the former (4,5).In addition to the increased risk of developing autoimmune hypothyroidism with age (2,6), children with DS have a higher chance of displaying a mild, isolated increase in thyroid-stimulating hormone (TSH) in the absence of low free thyroxine (FT4) or overt hypothyroid symptoms (7,8). This phenomenon, of uncertain etiology, can be referred to as subclinical hypothyroidism (SH) and seems usually to be transitory and self-limiting without treatment (9,10). However, there are few systematic studies on SH, and the factors related to its remission are unclear. The possibility that thyroxine replacement may have a beneficial effect on the somatic and psychomotor development of patients with DS and SH has been raised (11). In this context, the results of a randomized, double-blind clinical trial with 196 DS children are important with respect to previous studies. On the basis of the theory that all DS subjects have slight hypothyroidism at birth (12,13), this study evaluated the effect of systematic treatment with levothyroxine initiated in the neonatal period and continued during the first 2 y of life, as compared with that of placebo. Treatment with levothyroxine resulted in a subtle improvement in psychomotor developme...
