Low molecular weight thyroglobulin leading to a goiter in a 12-year-old girl

Abstract

We characterized the abnormal thyroglobulin (TG) in the thyroid and serum of a 12-yr-old girl with a large sporadic multinodular goiter first noted at age 4 yr. She developed normallyand had no clinical evidence of hypothyroidism. However, her serum T4 was less than 1.0/µg/dl, T3 was 125 ng/ dl, and TSH was 155 µU/ml. Serum PBI was 9.7 /µg/dl, and more than 90% was not extractable with butanol. The 24-h radioactive iodine uptake was 55%, not dischargeable by perchlorate. Hormone formation was tested by the administration of 131I before surgery. [131I]T4 and [131I]T3) but not 131I-labeled iodotyrosines, were present in the thyroidal venous blood. Hydrolysis of 10,000 × g supernatants from three randomly obtained samples of the goiter revealed 66–77% of the 131I asiodotyrosines, 2–4% as iodothyronines, and 10–12% as undigestable material; the MIT to DIT ratio ranged from 3.1–8.7, and the T4 to T3 ratio rangedfrom 2.3–8.3. The TG level was 2.5 mg/g in the goiter and 9.4 /µg/ml in the seru