Endocrine Abstracts

Introduction: Although incidentalomas in endocrine glands such as pituitary, adrenal or thyroid are well defined, parathyroid incidentaloma is a rare concept. In this study, we aimed to determine the prevalence of suspicious parathyroid lesions and true parathyroid incidentalomas in patients referred for thyroid ultrasonography (US) and investigate the possible factors that might cause inadvertent suspicion of a parathyroid adenoma.

Methods: Patients suspected to have parathyroid lesions during thyroid US were recorded prospectively between August 2009 and January 2010. Patients referred for parathyroid US and patients with known high serum calcium or parathyroid hormone (PTH) levels were excluded. Suspected parathyroid lesions were defined as hypoechoic homogeneous solid lesions with regular margins located outside the thyroid lobe, most commonly inferior to the thyroid gland.

Results: Thyroid US was performed in 6528 patients during the study period. There were 78 patients (1.19%) (73 female and 5 male) with suspected parathyroid lesion and the mean age was 45.32±12.59. The diagnosis of a true parathyroid adenoma was confirmed six (7.69%) patients. Mean serum calcium, phosphorus and PTH levels were 10.57±0.48 mg/dl, 3.03±0.52 mg/dl and 182.91±46.62 pg/ml respectively in patients with true adenoma. Among 72 patients with false positive parathyroid lesion, antithyroid peroxidase antibody was positive in 50 (69.4%), antithyroglobulin antibody was positive in 46 (63.9%) and one of these antibodies were positive in 59 (81.9%) patients. Also, 46 (63.9%) of 72 patients had thyroid dysfunctions (43 hypothyroidism and 3 hyperthyroidism) and 59 (81.9%) had chronic thyroiditis ultrasonographically.

Conclusions: Parathyroid incidentaloma was detected in 0.09% of patients referred for thyroid US. Presence of clinically or ultrasonographically chronic thyroiditis seems to be the major factors related to inadvertent interpretation of a hypoechoic lesion as a parathyroid pathology during thyroid US. Most of these lesions are probably lymphadenopathies that may occur commonly in patients with chronic thyroiditis.