THE CONTENT OF THYROID HORMONES AND OTHER IODINATED COMPOUNDS IN THYROID TISSUE IN AUTOIMMUNE THYROIDITIS

Abstract

ABSTRACT The total iodine content and the content of iodocompounds in the thyroid gland were studied in 9 patients with autoimmune thyroiditis. The thyroids were labelled in vivo with radioactive iodine before surgical biopsy. Five grams of tissue were homogenized and the iodocompounds were separated both by paper chromatography and on a cellulose column. The distribution profile of both the radioactive and the stable compounds was determined. The thyroid tissue contained on an average 11.0 ± 8.0 (sd) per cent of radioactive and 15.0 ± 9.4 per cent of stable iodothyronines. The MIT/DIT ratio was 1.16 ± 0.26 for the radioactive and 0.92 ± 0.30 for the stable compounds. Clinically evident hypothyroidism occurred only in patients with a very low iodine content and was not correlated with the proportion of iodothyronines found in the thyroid tissue. For instance, in two hypothyroid patients the iodothyronines corresponded to about 20 per cent of the iodocompounds of the tissue. These findings suggest that iodine depletion of the thyroid gland plays an important role in the development of clinical hypothyroidism in autoimmune thyroiditis and that up to a very late stage of the disease the thyroid is evidently capable of producing iodothyronines in fairly normal proportions.