Endocrine Abstracts

To examine use of I¹³¹ therapy we conducted a retrospective analysis of patient case notes that received I¹³¹ between May 2002 and Dec 2003.

46 patients received radioiodine therapy during 18 months. All had a prior thyroid uptake scan confirming their diagnosis and written informed consent obtained.

Results: GD: 29 patients (18F:11M; aged 52.6±2.8 yrs). 11 had a FT3 of <10 pmol/L pre radioiodine (38%). 25 received I¹³¹ at a dose of dose 400–550 MBq, 2 received <400 MBq, 2 received >550 MBq. 4 had eye signs; none received steroids at the time of I¹³¹ with no worsening of opthalmopathy although none became profoundly hypothyroid post I¹³¹. 18 had TFTs checked within 8 weeks of radioiodine (62%). At 12 months 23 were on thyroxine replacement and 2 were euthyroid. 2 required a second dose of I¹³¹ and became hypothyroid within 3 months.

TMNG: 9 patients (8F:1M; aged 70.2±2.7 yrs). 5 had a FT3 of <10 pmol/L pre radioiodine (56%). 5 received >550 MBq I¹³¹ and 4 received <550 MBq. 6 had TFTs checked within 8 weeks of radioiodine (67%). At 12 months 5 were euthyroid and 2 were on thyroxine replacement; 2 remained hyperthyroid, one of which required a second dose of I¹³¹.

TA: 8 patients (6F: 2M; aged 58.5±5.6 yrs). All had a FT3 <10 pmol/L pre radioiodine. 6 received I¹³¹ at a dose of 300–500 MBq, and 2 received >500 MBq. 5 had TFTs checked within 8 weeks of radioiodine (63%). At 12 months 7 were euthyroid. 1 required a second dose of I¹³¹ and became permanently hypothyroid.

Conclusions: Our findings emphasize the importance of checking TFTs within 8 weeks of I¹³¹ to detect hypothyroidism, particularly in patients with Graves’. Repeat doses of I¹³¹ may be prevented by ensuring theraputic first doses, as 2 of our 4 patients who required second doses initially received less I¹³¹ than recommended by the RCP.