Endocrine Abstracts

Aims: To look at the demographics, biochemistry, treatments used, clinical characteristics associated with radioiodine (RI) treatment (including those with relapse) for thyrotoxicosis in our Endocrine clinic.

Methods: Electronic records of all thyrotoxic patients between 2010 and 2012.

Results: 144 patients, mean age 56 years (114 females)–106 Graves, 24 toxic adenoma (TA) and 14 multi nodular goitre (MNG). TPO antibody was positive in 104/144 (72%) patients. At baseline, 6 and 12 months respectively mean FT₄ was 23.4, 15.25 7 16.9 pmol, mean FT₃ was 8.3, 5.9 and 5.6 pmol and TSH 1.09, 25.5 and 8.13 IU/l.

26/144(18%) had dysthyroid eye disease and 15/144 (10%) post radioiodine treatment (only three patients needed steroids). 7/26 (3%) with eye disease were smokers. 24/31(77%) smokers had no eye problems. Mean anti thyroid drug (ATD) duration was 12.7 months before RI (25/144 – 17% did not need RI).

Transient hypothyroidism developed in 57/119 (48%) patients, 5 months after RI. Permanent hypothyroidism developed in 62/119 (52%) patients, average 5 month after RI treatment.

6/119 (5%) needed second RI dose – average age 57 years, all females, mean FT₄ at baseline was higher (44 vs 23.4 pmol whole group), mean ATD duration was higher (42 vs 12.7 months whole group), three had TA and three Graves, all six were pre treated with carbimazole (two also needed propylthiouracil) and the average gap between two RI treatments was 2 years.

Conclusions: 83% of our thyrotoxic patients needed RI following 12 months of ATD treatment. Prevalence of transient hypothyroidism was expected but 50% developed permanent hypothyroidism within 6 months of RI use – likely related to the higher radioablative dose currently being used (600–650 MBq). Perhaps for the same reason, only 5% of our cohort required second RI dose – these patients had a much higher baseline FT₄ and needed ATD for at least 3.5 years.