Long-term effect of iodized oil on serum thyroglobulin levels in endemic goitre patients.

Serum thyroglobulin (Tg) response to bovine TSH (bTSH) was evaluated in 44 goitrous patients (grades III and IV) living in conditions of chronic iodine (I) deficiency (iodine urinary excretion less than 40 micrograms I/g) and in 26 normal subjects. After the initial clinical evaluation and laboratory tests (bTSH test, T4, T3, anti-Tg and anti-microsomal antibodies) all goitrous patients received 1 ml i.m. of iodized oil (I-oil) and were followed up for 30 months. The bTSH test was repeated at 6, 12, 20 and 30 months after I-oil in 21 subjects. A marked reduction in goitre size was observed in 85% of the patients with a concomitant significant increase in the mean serum T4 and T3 concentrations, a significant fall in the mean serum TSH level and a significant decrease in the T3/T4 ratio. Goitrous patients had elevated serum basal Tg levels (55 +/- 8 SEM micrograms/l) and a significantly mean higher peak Tg value after bTSH (200 +/- 65 micrograms/l) as compared with normal subjects (respectively, 11 +/- 1.4 and 32 +/- 3.4 micrograms/l). Larger goitres (grade IV) had a significantly higher mean peak Tg response as compared with grade III goitres. Treatment with I-oil significantly reduced the mean peak Tg response to bTSH after 6 months (59 +/- 10 micrograms/l) but at 12 and 20 months the peak Tg response after the injection rose, respectively, to 110 +/- 19 micrograms/l and 92 +/- 14 micrograms/l (P less than 0.02 as compared with 6 months), returning to the normal range only at 30 months.(ABSTRACT TRUNCATED AT 250 WORDS)