Endocrine Abstracts

Introduction: The cause of primary hyperparathyroidism (PHPT) is a single adenoma in 85% of cases. Scintigraphy with technetium-sestamibi (MIBI) is the test of choice for localising adenomas in patients with PHPT, allowing minimally invasive surgery in most patients. Some articles recommend thyroid function supression to improve scintigraphy results.

Methods: A prospective study was conducted in which 8 patients were included with diagnosis of PHPT and negative scintigraphy for adenoma localisation. These patients did not have a contraindication for thyroid hormone intake. We started treatment with a dose of 1 mcg/Kg per day with dose titulation until achievement of TSH<0.3 μU/ml. Once the objective was reached, MIBI was repeated with the same technique and interpreted by the same specialist in Nuclear Medicine.

Results: 75% of patients were women, mean age 51.9±20.55 years.

De los eight pacientes incluidos en el estudio, 6 eran mujeres (75%), con una edad media de 51.9±20.55 años. Mean preoperative calcium level was 11.49±0.61 mg/dl. Mean preoperative PTH level was 146.26±97.58 ng/l. Mean TSH level before repeating scintygraphy was 0.17±0.08 μU/ml. Thyroxine suppression scan was positive in four of the eight patients (50%). Only two of these four patients underwent surgery for the moment. Minimally invasive surgery was performed in these cases, confirming the existence of a parathyroid adenoma where the MIBI suggested. The level of calcium in these patients normalized after surgery.

Conclusiones: In our study suppression of thyroid function by thyroxine administration improved MIBI sensitivity for parathyroid adenoma localization in our patients with previous negative studies, however, a larger number of patients would be required to confirm these results.