The coexistence of primary hyperparathyroidism and thyroid nodules: should the preoperative work-up of the parathyroid and the thyroid diseases be specifically adjusted?

Primary hyperparathyroidism (PHPT) can be found in concomitance with thyroid disease (TD) in a high frequency of cases. In this context the diagnostic exams for localizing the enlarged parathyroid(s) gland(s) could be less reliable or nonconclusive. Moreover, the thyroid carcinoma seems to be more frequent compared to that isolated thyroid desease and, therefore, carefully investigated. The main goal of the present study is to evaluate which diagnostic tool (US, MIBI) is more reliable for localizing the site of the PTH hypersecretion and to confirm if it is always advantageous a combination of both exams. Besides, we evaluated the incidence of thyroid carcinoma in our series of patients. A review of available data of 73 patients who underwent total thyroidectomy + parathyroidectomy from 2003 and 2014 was performed. The preoperative workup included systematically US and MIBI whose results were considered true positive when at least the side (left/right) of the parathyroid affected were concordant with the surgical report, settled as the gold standard, according to the Cox nonnested model. The connection between the diagnostic results of US versus MIBI was calculated with the Cohen K index for evaluating their overlap. The average of the thyroid carcinoma were also calculated. The difference between respectively US versus surgical report (p value=0.73) and MIBI versus surgical report (p value=0.81) were not significant. The low Cohen K index showed that both US and MIBI are complementary. In 23 patients (32,9%) a thyroid carcinoma was found. The association of MIBI and neck US is mandatory in the first evaluation of patients undergoing thyroidectomy and parathyroid excision simultaneously. The high prevalence of thyroid carcinoma in this specific context suggests a more aggressive diagnostic and surgical behaviour.