A PROSPECTIVE-STUDY OF THE EFFECT OF NONIONIC CONTRAST-MEDIA ON THYROID-FUNCTION

To observe the effect of iodine in nonionic contrast media on thyroid function, we measured free thyroxine (FT4) and thyroid stimulating hor mone (TSH) following nonionic contrast radiography in 73 patients (49 males; 24 females) aged 50 to 84 years, mean 65.7 years. FT4 was signi ficantly (p < 0.01) raised above baseline at 8 weeks but not 4 weeks f ollowing contrast injection (mean +/- standard deviation, 17.1 +/- 5.9 and 14.3 +/- 4.0 vs 13.3 +/- 2.7 pmol/L at baseline); however, TSH wa s significantly (p < 0.03) depressed at both 4 and 8 weeks (1.09 +/- 0 .68 and 1.21 +/- 1.56 vs 1.40 +/- 0.90 mlU/L). T-3 did not change sign ificantly. FT4 rose by more than 20% in 15/73 and TSH fell by more tha n 20% in 41/73 compared to a fall of FT4 in 3/73 and a rise in TSH of 8/73 (P < 0.005 and < 0.001, respectively). Two patients became hypert hyroid and in four others either FT4 was elevated or TSH suppressed, o ne of whom developed atrial fibrillation. Although frank hyperthyroidi sm following contrast radiography was uncommon, there was a significan t trend towards thyroid stimulation rather than suppression after iodi ne exposure. This may be related to the age of the patients studied.