ENDEMIC GOITER IN PEDREGOSO (Chile)
ABSTRACT A survey on goiter was carried out in Pedregoso, an isolated Indian Reservation in the Chilean Andes. A palpable goitre was present in 84 per cent of the adult population. All subjects were clinically euthyroid and had a normal contraction time of the Achilles tendon reflex. The mean value for serum PBI was 5.06 μg/100 ml, with 22% of the cases having values below 4 μg. Iodine deficiency was established by its low concentration in drinking water (0.35 μg/liter) and in the urine (33 μg/24 h). Radioiodine studies showed an average thyroid uptake of 68% at 24 h with a tendency to increase directly with thyroid size and to decrease with age. Serum labelled PBI reflected different radioiodine turnover rates, highest values being more frequent in large nodular goitres. Triiodothyronine (T3) suppression tests were negative in about one-third of the goitrous subjects. Perchlorate tests and antithyroid antibodies determinations consistently gave negative results. Thyroxine (T4) was always the main labelled compound, T3 being significantly present in 9 out of 22 cases. Up to 18% of the circulating radioiodine at 48 h was not butanol-extractable, and appeared in the initial fraction of column chromatography analysis. Six out of 58 cases also showed endogenously labelled diiodotyrosine (DIT), which constituted up to 10% of the total circulating radioiodine at 48 h. After intravenous injection of a tracer dose labelled DIT, 5.8 per cent ± 0.51 of the dose was excreted unchanged in the urine within 2 h. The highest values were observed in the largest goitres. The extra-thyroid organic iodine compartment was investigated after the injection of labelled T4 and T3. An increase in fractional turnover rate was always observed associated with an increase in the thyroxine distribution space.