Endocrine Abstracts

Background: Radionuclide thyroid scanning using technetium pertechnetate (Tc^99m) is a useful aid in the differential diagnosis of benign thyroid disease. It is particularly useful in the differentiation of the causes of a thyrotoxic biochemical picture, e.g. viral thyroiditis, toxic nodular disease or Grave’s disease. This has implications for long-term management plans. However, its cost and exposure to radiation necessitate the need to justify its use in the investigation of thyroid disease.

Methods: A retrospective study of 70 Tc^99m reports was performed. Indications for the scan and the results were recorded. All Tc^99m scans were performed in the same nuclear medicine department.

Results: The indications for requesting a Tc^99m scan included the differential diagnosis of thyrotoxicosis in 39 (55.7%) patients, subclinical thyrotoxicosis in 22 (31.4%) patients and 9 (13%) further scans were performed but the indications were not clear and probably unjustified.

Of 39 scans performed to define the cause of thyrotoxicosis, 16 (41%) showed multinodular disease, 15 (38.5%) Grave’s disease, 1 (2.5%) thyroiditis and 7 (18%) were indeterminate.

Of 22 scans performed to define the cause of a persistently suppressed TSH with normal free T₄ and free T₃, 14 (63.6%) showed features of nodular autonomy, 3 (13.6%) were consistent with Grave’s disease, 1 (4.5%) showed a mediastinal ectopic hot spot and 4 (18.2%) were reported as showing normal uptake.

Of the 14 patients suspected of having Graves’ disease clinically, 9 (64.3%) were confirmed to have features consistent with Graves’ disease on Tc^99m scanning.

Conclusion: Technetium scan can be useful as a supplementary investigation to clinical, biochemical and ultrasound examination in aiding the differential diagnosis of thyroid disease and subsequent planning of therapy. There should be clear guidelines on the appropriate use of this modality to avoid unnecessary exposure to radiation and cost. We intend to set such guidance locally.