From John L. Birks
As a retired medical physicist who was formerly much involved with the diagnosis and treatment of thyroid illnesses, I think your article gave a misleading impression of the situation, and risks causing patients undue alarm (6 March, p 10).
Some decades ago, patients with Graves disease would undergo a series of diagnostic tracer tests to establish the size of the gland, the distribution of radio-iodine, and the uptake and rate of turnover. They would then be given a treatment dose of iodine-131 that was tailored to each patient individually, with the aim of producing a euthyroid state. But it was found that this could leave the patient in a hyperthyroid condition, requiring a second treatment dose.
So more recently, as your article reports, medical opinion has swung in favour of giving most patients an “ablative dose”, which will quickly correct the overactive thyroid and within weeks produces a hypothyroid state, which can be easily controlled by a maintenance dose of thyroxine.
Endocrinologists, aware of possible heart problems associated with long-term overactive thyroids, often preferred this approach as giving a more certain outcome. The quantity of radio-iodine would generally be larger than that calculated to produce a euthyroid state, and this is what your article picks up on.
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The decision to use an ablation dose rather than a dose tailored to an individual patient has to be made on clinical grounds, and it would be wrong to call it an overdose.
Having said that, if I were to suffer from hyperthyroidism, I would prefer to be given a dose tailored to produce a normal thyroid, without having to rely on the lifelong use of thyroxine.
Swansea, UK
