Parathyroid incidentaloma detected during thyroid sonography - prevalence and significance beyond images

Parathyroid incidentaloma (PTI) designates a nodule discovered incidentally during thyroid sonography, and whose location and aspect suggests an abnormal parathyroid. Our aim was to assess the prevalence of PTI, their functional characteristics and to identify the factors correlated with their presence.

We recorded all patients detected with PTI between January 2009 and December 2011, in our department. Serum calcium, parathyroid hormone (PTH), thyroid stimulating hormone (TSH), free thyroine (FT4) and anti thyroid peroxidase antibodies (anti-TPO Ab) were measured.

From a total of 2662 thyroid ultrasounds, 32 patients were identified with PTI (prevalence 1.2%). The diagnosis of a functional parathyroid adenoma was confirmed in 12 patients (37.5%). There was no significant difference in size, location, echogenicity or vascular pattern between the functioning adenomas and the other PTI. The only parameter correlated with the non functioning lesion was the multinodular pattern of the thyroid (multinodular goiter or macronodular autoimmune thyroiditis).

Although rare, the ultrasound identification of an image suggestive for a pathological parathyroid gland requires the evaluation of the functioning character of the lesion, more than one third PTI being hyperfunctional. The concomitance of a nodular goiter decreases the probability of a primary hyperparathyroidism.