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Selenium decreases thyroglobulin concentrations but does not affect the increased thyroxine-to-triiodothyronine ratio in children with congenital hypothyroidism

par Chanoine, Jean-Pierre ;Neve, Jean ;Wu, Sy;Vanderpas, Jean-Baptiste ;Bourdoux, Pierre
Référence The Journal of clinical endocrinology and metabolism, 86, 3, page (1160-1163)
Publication Publié, 2001

Article révisé par les pairs

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Résumé :

Compared with euthyroid controls, patients with congenital hypothyroidism (CH) who are receiving L-T4 treatment show elevated serum TSH relative to serum T4 concentrations and increased T4/T3 ratio. These abnormalities could be the consequence of impaired activity of the selenoenzymes deiodinases on which patients with CH rely to convert the ingested L-T4 into active T3. Eighteen patients (0.5-15.4 yr), diagnosed with CH in infancy, received selenomethionine (SeM, 20-60 μg selenium/day) for 3 months. The study took place in Belgium, a country where selenium intake is borderline. Compared with the values observed in age- and sex-matched euthyroid controls, patients with CH had decreased selenium, thyroglobulin and T3 concentrations and increased TSH, reverse T3, and T4 concentrations and T4/T3 ratio at baseline. Selenium supplementation caused a 74% increase in plasma selenium values but did not affect the activity of the selenoenzyme glutathione peroxidase used as a marker of selenium status. SeM abolished the TSH difference observed between CH patients and euthyroid controls at baseline and caused a significant decrease in thyroglobulin values. Thyroid hormone concentrations were not affected by SeM. In conclusion, our data suggest that selenium is not a limiting factor for peripheral T4-to-T3 conversion in CH patients. In contrast, we find indirect evidence that SeM improves thyroid hormones feedback at the hypothalamo-pituitary level and decreases stimulation of the residual thyroid tissue, possibly suggesting greater intracellular T4-to-T3 conversion.