Endocrine Abstracts

Radioactive iodine is a common and effective treatment for hyperthyroidism. Post radio-iodine hypothyroidism is a frequent complication occurring in ~80% of radioiodine treated patients. This can be diagnosed clinically (by monitoring free T₄ and TSH levels) but, in our centre, a ¹²³I uptake scan 6 weeks after therapy is sometimes used to help predict the likelihood of future hypothyroidism. In these situations, thyroxine therapy can be started if radioiodine uptake <2% even if thyroid biochemistry is normal. We investigated the effectiveness of 6 weeks radioiodine uptake scans in avoiding delayed recognition of hypothyroidism by auditing all patients who underwent ¹³¹I treatment at our centre in 2007.

We reviewed case notes and biochemistry of all patients who underwent ¹³¹I therapy for hyperthyroidism in the Western Infirmary, Glasgow during 2007. Statistical analysis was performed using Minitab software.

Forty-two patients were eligible for study; of these 20 had a ¹²³I uptake scan performed 6 weeks later. A summary of clinical details including indications for therapy is seen below.

The data suggest that use of a diagnostic ¹²³I uptake scan 6 weeks after radioiodine treatment may expedite diagnosis of hypothyroidism resulting in earlier prescribing of thyroxine and avoidance of prolonged untreated hypothyroidism. Therefore, in centres where such facilities are available we would continue to advocate routine ¹²³I uptake scan as well as thyroid biochemistry at the first clinic visit after radioiodine therapy.