INCREASED PEROXIDASE-ACTIVITY IN PENDREDS SYNDROME WITH HYPOTHYROIDISM

An 8 yr old boy with goiter and bilateral nerve deafness had a 46% discharge of radioiodine after thiocyanate administration. He was clinically euthyroid. Although the serum total T4 [thyroxine] was low (2.4 .mu.g/100 ml) and TSH [thyrotropin] was significantly high (181 .mu.U[.mu.units]/ml), the serum total T3 [triiodothyronine] was normal (152 ng/100 ml). The increased release of TSH by the feedback mechanism in response to the low T4 probably resulted in a normal level of serum T3. The thyroid gland demonstrated a low stable I content, an increased MIT/DIT [monoiodotyrosine/diiodotyrosine] ratio and a decrease in iodothyronine. The thyroglobulin behaved normally in Sephadex G-200 chromatography and immunoreaction. Thyroid tissue exhibited increased peroxidase activity as measured by I3 formation. Increased peroxidase activity may be related to the observed increase in serum level of TSH.