Association of peroxidase enzyme defect and low thyroglobulin content in a case of endemic cretinism

Abstract

Neurological endemic cretinism is highly prevalent in severe endemic goiter areas. Often associated to euthyroid goiter, it is probably related to iodine deficiency. However the exact pathogenetic mechanism is yet unclear. We report the biochemical study of thyroid tissue obtained from a 26 year-old female cretin with a grade III multinodular goiter, neurological signs and euthyroidism. After surgery, thyroid tissue was analysed: iodoproteins where characterized by gel filtration, electrophoresis, sedimentation coefficient and antigenicity. Iodoalbumin was predominant while thyroglobulin was quantitatively reduced and poorly iodinated. In vitro, iodination with hog thyroid peroxidase was normal. There was no difference in peroxidase affinity for iodide in the oxidation reaction but a significantly reduced ability to iodinate in vitro thyroglobulin and free tyrosine. Oxidation of acetyltyrosilamide into bityrosine was also markedly reduced. These abnormal findings are known to occur in sporadic cases with or without hypothyroidism. The neurological defects could be linked to transient hypothyroidism during the critical period of nervous system maturation, however a role of iodine deficiency per se cannot be ruled out.