Endocrine Abstracts

Context: Cervical ultrasound is a frequently used and an accessible operator-dependent tool, which contributes to the characterization of thyroid nodules and to the preoperative localization of pathological parathyroid glands. However, thyroid nodules may be confused with parathyroid lesions. There is no study directly comparing thyroid and parathyroid nodules on ultrasound.

Objectives: 1) To describe the ultrasonographic characteristics of parathyroid lesions and to establish bio-radiological correlations; 2) to identify specific features differentiating them from thyroid nodules, by using the EU-Tirads ultrasound stratification scoring risk.

Patients/Methods: PARATH-US is a single-center study. We included 160 parathyroid lesions proved biologically (through intranodular PTH measurement) or histopathologically after surgical excision and compared them with 169 age, sex and maximal diameter-matched thyroid nodules in patients undergoing ultrasound examination in the Endocrinology Department of Bicêtre Hospital from 2016 to 2022.

Results: 160 parathyroid lesions belonging to 141 patients (53.8±18.5 years, 104 women, serum calcium levels 2.94±0.33 mmol/l, PTH levels 377.9±614.6 ng/l) were included. 66.4% of them were adenomas, 27.6% hyperplasias, 4.3% atypical adenomas. The maximal diameter of parathyroid lesions was 14.3±7.5 mm, their volume 0.89±2.18 ml. 62.7% of the lesions were solid, 85.4% were separated from the thyroid parenchyma by a hyperechoic septum and 56.7% had intra-nodular vascular spot. Parathyroid hyperplasias were smaller (0.57±0.76 vs 1.31±2.74 cm3, P=0.037) and had less vascular spots (26% vs 73.5% P=0.004) than adenomas. In patients harboring a unique parathyroid lesion, strong positive correlations were found between serum calcium, PTH levels and lesion diameter/volume (r>0.58 and P<0.001 for all comparisons). Parathyroid lesions more frequently presented an anterior hyperechoic septum than thyroid nodules (85.4 vs. 5.2%, P<0.0001, positive predictive value (PPV) set at 99% [95% CI 97-100]). Parathyroid lesions presented with various morphologies, and had more often a non-oval shape than thyroid nodules (55.8 vs. 17.4%, P<0.0001, PPV 82% [75-87]). Marked hypoechogenicity (EU-Tirads 5) was found more often within parathyroid lesions (41.2%) than thyroid nodules (18.9%, P<0.01, PPV 67% [59-74]). Conversely, the prevalence of kystic content was found more frequently in thyroid than in parathyroid nodules (12,4% vs. 3,6%, P=0.0037).

Conclusion: We describe the ultrasound characteristics of a large series of parathyroid adenomas/hyperplasias. We show that parathyroid lesions present high-risk ultrasound features, if confused with thyroid nodules. We demonstrate the presence of specific morphological ultrasound characteristics, which help differentiating parathyroid from thyroid lesions