Linear growth and intellectual outcome in children with long-term idiopathic subclinical hypothyroidism

Objective: The treatment of children with subclinical hypothyroidism (SH) is controversial for TSH values between 4.5 and 10 mU/l. The aim of this cross-sectional, controlled study was to evaluate growth and intellectual outcome in children with persistent SH who have never been treated with levothyroxine. Design and methods: Clinical and auxological parameters, thyroid function, and intellectual outcome were evaluated in 36 children with persistent SH at the age of 9.7 +/- 0.6 (range 4-18.0) years. Children had been followed longitudinally for 3.3 +/- 0.3 (range 2.0-9.3) years, from first diagnosis of SH until enrollment in the study. Thirty-six age-and sex-matched children were enrolled in the study as controls. Results: At study entry, height (-0.8 +/- 0.2 SDS), bone age/chronological age (BA/CA ratio 0.92 +/- 0.6), and body mass index (BMI -0.1 +/- 0.2 SDS) in SH children were normal. Despite long-term duration of SH, none of these parameters showed a worsening with respect to height (-0.7 +/- 0.2 SDS), BA/CA (0.97 +/- 0.03), and BMI (-0.1 +/- 0.2) at the time of first SH detection. None of the children showed overt signs or symptoms of hypothyroidism during the follow-up. Verbal (99.1 +/- 2.2), performance (100.4 +/- 1.9), and full-scale (99.7 +/- 1.9) intelligence quotient (IQ) scores in SH children were normal and comparable to those of controls. No relationship was detected between IQ scores and the degree or duration of SH. Conclusions: Persistent SH in children is not associated with alterations in growth, bone maturation, BMI, and cognitive function or other complaints that could be ascribed to SH even after several years without therapeutic intervention.