Endocrine Abstracts

Radioiodine(RI) is an effective treament for thyrotoxicosis, being used with increasing frequency. Since 1998 an initial dose of 400 MBq has been used in the treatment of thyrotoxicosis, with a standard second dose of 550 and third dose of 799 MBq. The efficacy of this dosing regimen in controlling hyperthyroidism was studied by a questionnaire survey of the GPs of 259 patients treated between November 1998 and January 1999. RI was deemed a success if patients were rendered euthyroid or hypothyroid.

Completed questionnaires were received on 183 patients: 83% female, mean age 61.5 years(male: 54.5 years). 145 patients received 400 MBq, 33 patients 550 MBq and 5 patients 799 MBq.

Treatment was deemed a success in 164 (90%) patients: 34 (19%) were euthyroid on no treatment and 130 (71%) had been rendered hypothyroid. No age or sex related subgroup could be identified as significantly more likely to develop hypothyroidism. The majority (61%) developed hypothyroidism within six months of therapy. Treatment was deemed a failure in 19 (10%) patients: 5 (3%) remained on carbimazole or propylthiouracil; 5 (3%) had had thyroid surgery and 11 (6%) required a second dose of RI. Of these, there was a wide spread of intervals between the first and second treatments, of 3-32 months. No age or sex related subgroup could be identified as significantly more likely to require a second dose.

These data demonstrate that the strategy of employing a 400 MBq initial dose for treatment of thyrotoxicosis achieves a high cure rate, with most patients subsequently requiring thyroxine replacement being identified within six months.