Abstract
Fourteen hypothyroid children, 10 girls and 4 boys, had serum T4, T3 and TSH measured while receiving replacement therapy with desiccated thyroid and 6 weeks after beginning replacement therapy with sodium-l-thyroxine, 4.2±0.6(SD) μg/Kg per day (maximum 200 μg). Serum T3 while receiving desiccated thyroid was 393±144(SD) ng/dl compared to 157±23(SD) ng/dl while receiving thyroxine (P<0.01). Serum T3 exceeded 220 ng/dl in 13 patients on desiccated thyroid. All serum T3 concentrations were within the normal range on thyroxine. Therapy with both thyroid and thyroxine resulted in normal T4 and TSH concentrations. However, the mean T4 concentration on desiccated thyroid was 7.4±2.0(SD) μg/dl compared to 11.7±2.5(SD) μg/dl while receiving thyroxine (P<0.01). Mean TSH concentration was 1.3±1.2(SD) μU/ml on thyroid and 1.6±1.1(SD) μU/ml on thyroxine (P>0.1). Our findings show that a paradoxically elevated serum T3 concentration, unassociated with clinical hyperthyroidism is, in general, characteristic of treatment with desiccated thyroid. Replacement with sodium-l-thyroxine leads to normalization of all routine tests of thyroid function.
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Penny, R., Frasier, S. 324 TRI-IODOTHYRONINE (T3) ELEVATION DUE TO DESICCATED THYROID. Pediatr Res 12 (Suppl 4), 417 (1978). https://doi.org/10.1203/00006450-197804001-00329
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DOI: https://doi.org/10.1203/00006450-197804001-00329