Selenium decreases thyroglobulin concentrations but does not affect the increased thyroxine-to-triiodothyronine ratio in children with congenital hypothyroidism.
Compared with euthyroid controls, patients with congenital hypothyroidism (CH) who are receiving L-T(4) treatment show elevated serum TSH relative to serum T(4) concentrations and increased T(4)/T(3) 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-T(4) into active T(3). Eighteen patients (0.5-15.4 yr), diagnosed with CH in infancy, received selenomethionine (SeM, 20-60 microg 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 T(3) concentrations and increased TSH, reverse T(3), and T(4) concentrations and T(4)/T(3) 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 T(4)-to-T(3) 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 T(4)-to-T(3) conversion.
Children's Hospital Reine Fabiola, B 1020 Brussels, Belgium. jchanoine@cw.bc.ca
J P
JP
Chanoine
J
J
Nève
S
S
Wu
J
J
Vanderpas
P
P
Bourdoux
D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D003409:Congenital Hypothyroidism; D019587:Dietary Supplements; D005979:Glutathione Peroxidase / Q000097:blood; D006801:Humans; D007037:Hypothyroidism / Q000097:blood / Q000188:drug therapy; D007223:Infant; D012643:Selenium / Q000097:blood / Q000172:deficiency / Q000627:therapeutic use*; D012645:Selenomethionine / Q000008:administration & dosage / Q000627:therapeutic use; D013954:Thyroglobulin / Q000097:blood*; D013974:Thyroxine / Q000097:blood* / Q000627:therapeutic use; D014284:Triiodothyronine / Q000097:blood*; D014285:Triiodothyronine, Reverse / Q000097:blood
D014284:Triiodothyronine; D014285:Triiodothyronine, Reverse; D013954:Thyroglobulin; D012645:Selenomethionine; D005979:Glutathione Peroxidase; D012643:Selenium; D013974:Thyroxine