A STEPWISE APPROACH TO LOCALIZATION STUDIES IN PRIMARY HYPERPARATHYROIDISM.

Purpose: Primary hyperparathyroidism (PHP) is a prevalent endocrine disorder requiring surgical treatment. The rise of minimally invasive parathyroidectomy as the favored surgical approach emphasizes the significance of localization studies. This study aims to explore clinical and laboratory profiles of PHP patients and evaluate the efficacy of diverse localization methods in a substantial patient cohort.

Methods: We analyzed clinical features, biochemical parameters, and imaging outcomes for localization, as well as postoperative histopathological findings in 327 diagnosed PHP patients who underwent surgery. Initial localization methods, which included ultrasonography (US), US-guided Parathormone (PTH) washout analysis, and 99mTechnetium-Sestamibi/123Iodine Scintigraphy (MIBI-SPECT/CT), were applied to all patients. Advanced techniques like Four-Dimensional Computed Tomography (4D-CT) and 18F-Fluorocholine Positron Emission Tomography (18F-FCH PET/CT) were used for cases where initial methods failed and/or for secondary intervention.

Results: Minimally invasive surgery accounted for 74% (n=241) of cases. Histopathological analysis revealed single adenoma in 94.5% (n=309) patients, hyperplasia in 5.2% (n=17), and cancer in 0.3% (n=1). Adenoma volume showed a significant positive correlation with serum calcium and parathyroid hormone (PTH) levels (p<0.001). 82 and 26 cases required 4D-CT and 18F-FCH PET/CT respectively, for localization. Positive predictive values (PPV) for imaging modalities were: US (84.56%), US-guided PTH-washout analysis (87.30%), MIBI-SPECT/CT (92.1%), 4D-CT (81.94%), and 18F-FCH PET/CT (95.83%).

Conclusion: Serum calcium and PTH levels estimate adenoma size. Initial localization studies (i.e.US, PTH washout and, MIBI-SPECT/CT) effectively localized most adenomas. 4D-CT showed notable efficacy, and 18F-FCH PET/CT had the highest PPV for adenoma localization when the initial studies failed.