Subclinical hypothyroidism (SH) is biochemically defined as serum TSH levels above the upper limit of the reference range in the presence of normal free T4 (FT4) concentrations. While there is a general agreement to treat subjects with serum TSH levels above 10 mU/L, the management of mild form (TSH concentrations between 4.5 and 10 mU/L) is still a matter of debate. In children, mild SH is often a benign and remitting condition and the risk of progression to overt thyroid dysfunction depends on the underlying condition, being higher in the autoimmune forms. The major concern is to establish whether SH in children should always be considered an expression of mild thyroid dysfunction and may deserve treatment. Current data indicate that children with mild SH have normal linear growth, bone health and intellectual outcome. However, slight metabolic abnormalities and subtle deficits in specific cognitive domains have been reported in children with modest elevation of TSH concentration. Although these findings are not sufficient to recommend levothyroxine treatment for all children with mild SH, they indicate the need for regular monitoring to ensure early identification of children who may benefit from treatment. In the meanwhile, the decision to initiate therapy in children with mild SH should be based on individual factors.
Mariacarolina Salerno, Nicola Improda and Donatella Capalbo
Manuela Cerbone, Carmela Bravaccio, Donatella Capalbo, Miriam Polizzi, Malgorazata Wasniewska, Daniela Cioffi, Nicola Improda, Mariella Valenzise, Dario Bruzzese, Filippo De Luca and Mariacarolina Salerno
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.
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.
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.