[Thyroid suppression in patients with primary hyperparathyroidism: does it improve the pre-surgical scintigraphy localisation?]

Abstract

Introduction: Scintigraphy with technetium-sestamibi (MIBI) is the test of choice for localising adenomas in patients with primary hyperparathyroidism (PHPT). In some studies it has emerged that the increase in sensitivity of this test could be associated with a decrease in the uptake of the radiotracer by the thyroid gland. The aim of this study is to analyse our experience in patients with a negative scintigraphy with MIBI, and in whom the study was repeated after suppression of thyroid function with thyroxine.

Material and methods: A prospective evaluation was performed on 17 patients who, between January 2006 and April 2011, had PHPT and negative imaging using scintigraphy with MIBI and who had the test repeated after the administration of thyroxine. The scintigraphy data and the correlation with the findings in the surgical intervention are reviewed.

Results: The mean TSH at the time of repeating the MIBI was 0.12+0.1mlU/L. Of the 17 patients included, the scintigraphy under thyroid suppression was positive in 13 of them (76.5%), and in the other 4 (23.5%) patients no image suggestive of adenoma was found. In the cases where the MIBI was positive after suppression, the positive predictive value (PPV) was 100%.

Conclusion: Suppression of thyroid function by giving thyroxine can help to improve the sensitivity of MIBI in patients with previously negative scintigraphy studies and help in the minimally invasive treatment of patients with PHPT.