Thyroid hormone formation in ectopic thyroid gland. A case study.

Several steps of thyroid hormogenesis were studied on a subhyoid ectopic thyroid tissue in a case of compensated hypothyroidism with simultaneous sublingual and subhyoid ectopic thyroid. The patient, a 19-year-old girl, had normal values for serum T4, T3U and T3, and an elevated serum TSH level. The thyroidal 131I uptake was elevated both at 3 h and 24 h after oral 131I intake. No significant discharge of radioiodine was observed after perchlorate load. On the thyroid biopsy specimen, peroxidase activity was shown to be normal by both assays of guaiacol oxidizing and iodinating activity. Thyroglobulin was 19S and was normally iodinated in vitro with peroxidase. Iodine content of thyroglobulin was within the normal range. The mean percentage distribution of 131I administered 7 days prior to the biopsy showed no significant difference from the normal pattern. From these studies, no specific defects in thyroid hormogenesis could be detected in this case. It is suggested that abnormalities in thyroid function in this case are mainly due to insufficient functioning mass in the ectopic thyroid.