December 06, 2013
1 min read

Out-of-control RAI uptake

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Over a period of 6 weeks I received hard to believe results from radioactive iodine uptake in three patients with well-documented hyperthyroidism.

In each of them, the 6-hour uptake was 85% to 90% and 90% to 92% at 24 hours.

The third patient is the most surprising. When I referred her for management, her thyroid-stimulating hormone was low at 0.11 (reference range: 0.11-5.0), her free T3 very high at 19.4 (reference range: 2.2-4.0) and her free T4 was 4.20 (reference range: 0.71- 1.85).

Each of these three patients has done well post-ablation, but they do need and are taking thyroid replacement.

I am in discussion with the nuclear medicine radiologists about these unusual data, but none of us can find a satisfactory explanation. I have carefully gone through PubMed and found nothing that could explain these results and also looked at seemingly relevant articles in JCEM. I am still in the dark.

My excellent radiology colleagues are very careful in determining the appropriate dose of RAI and there was nothing unusual in these patients.

I have contacted some thyroid expert colleagues for an explanation but to date there is no meaningful answer.

As is often with my blogs, any advice you can provide is needed.