Control of thyroglobulin secretion in patients with ectopic thyroid gland.

Serum thyroglobulin (Tg) measurements were performed in 17 children with congenital hypothyroidism due to an ectopic thyroid gland before therapy and during follow-up. Data were analysed in four periods according to duration of therapy and compared to results obtained in a group of 51 normal children aged 1 month to 6 yr. At diagnosis serum Tg was higher than the mean normal value measured at a similar age. We observed a rapid and parallel decrease of both Tg and thyroid-stimulating hormone during the early weeks of therapy. However, Tg was always detectable in the serum of treated (euthyroid) patients. After 34 months of therapy serum Tg was 11.4 +/- 1 ng/ml, a value significantly different (p less than 0.001) from that obtained in normal controls of similar age (23.5 +/- 3 ng/ml). In nine treated children aged more than 2 yr, thyroid-stimulating hormone and Tg were increased after a brief period of decreased L-thyroxine dosage. These data indicate that ectopic thyroid tissue does not involute during thyroxine therapy and, in response to elevations of serum thyroid-stimulating hormone, can be stimulated to secrete Tg.