MULTIGLANDULAR PARATHYROID GLAND DISEASE: AN INCIDENTAL DISCOVERY IN NORMOCALCEMIC PATIENTS DURING THYROID SURGERY

Context: Several enlarged parathyroid glands could be found during thyroid surgery in normocalcemic patients without evidence of primary or secondary hyperparathyroidism, indicating multiglandular parathyroid gland disease (MGD).

Objective: Clinical role of various levels of serum ionized calcium (Ca²⁺) in patients diagnosed with incidental MGD during thyroid surgery remains controversial. The aim of the study was to evaluate the features of PHPT and the clinical role of serum Ca²⁺ in normocalcemic patients diagnosed with incidental MGD.

Study design: A prospective study of patients with normal preoperative Ca²⁺ to be operated on for thyroid diseases in 2010-2013 and diagnosed with MGD during thyroid surgery.

Methods: An analysis of clinical data from 3,561 patients to be surgically treated for thyroid diseases revealed 219 (6%) patients with MGD and normal serum Ca²⁺. Further data analyses showed patients with MGD and high normal (≥1.25 - 1.3 mmol/L) serum Ca²⁺ (n = 89) and with moderate-low (1.0 - 1.24 mmol/L) serum Ca²⁺ (n = 130).

Results: Primary hyperparathyroidism was diagnosed intra- and post-operatively in 48 (54%) patients with high-normal serum Ca²⁺ and in 2 (2%) patients with moderate-low serum Ca²⁺ (p<0.0001). Parathyroid hormone, serum Ca²⁺ as well as urine calcium excretion were elevated in 2 (2%) patients with moderate-low serum Ca²⁺ and in 18 (20%) patients with high-normal Ca²⁺ at follow-up (p<0.0001).

Conclusion: Serum Ca²⁺ level within the normal range, but higher than 1.25 mmol/L (high-normal) is associated with primary hyperparathyroidism, which should be considered in patients with visually diagnosed MGD, but without clinical symptoms of hyperparathyroidism.