Endocrine Abstracts

Objective

Primary hyperparathyroidism (PHPT) is the most common cause of hypercalcemia. A group of patients who were followed up with a diagnosis of PHPT had normal calcium levels with high parathyroid hormone (PTH) levels. For the diagnosis of normocalcemic PHPT, secondary causes of hyperparathyroidism such as vitamin D deficiency should be excluded. In this study, the data of 318 PHPT patients who were operated were retrospectively analyzed, and biochemical and clinical characteristics of hypercalcemic and normocalcemic patients were compared.

Methods

The data of patients who were admitted to our hospital’s endocrinology clinic between January 2012 and January 2019, diagnosed with PHPT and operated according to guidelines (all symptomatic patients and asymptomatic patients with at least one operation indication) were retrospectively evaluated. A total of 318 patients were divided into two groups as hypercalcemic and normocalcemic according to the corrected calcium level. The two groups were compared according to clinical and biochemical properties.

Results

Female gender was dominant in both groups (P = 0.07). The mean age was similar in both groups (P = 0.36), while it was 54.0 ± 10.3 in the hypercalcemia group, and 55.4 ± 12.8 in the normocalcemia group. As expected, serum corrected calcium (Ca), PTH levels and urinary Ca excretion were higher in the hypercalcemia group (P < 0.01). While phosphorus (P) level was lower in the hypercalcemia group (P < 0.01), urinary P excretion was similar between the two groups (P = 0.77). There was no difference between the two groups in alkaline phosphatase, creatinine, and vitamin D levels. Percentage of localization with preoperative ultrasonography and mean adenoma size were similar. Also, there was no difference in adenoma features (echogenicity, cystic appearance) and localization, thyroid nodules and thyroiditis prevalence on ultrasonography. The positive result obtained on neck MRI and MIBI scanning was similar. There was no difference between the two groups in terms of stone incidence and osteoporosis prevalance (P = 0.72 and P = 0.08, respectively).

Conclusion

In our cohort, corrected Ca and PTH levels and urinary Ca excretion were high in the hypercalcemic group, as expected. But, the phosphorus level was significantly lower in the hypercalcemia group. In the normocalcemic group, the PHPT phenotype was found to be similar to the hypercalcemic group. These findings suggest that the frequency of surgical indications is similar in normocalcemic PHPT patients to that in hypercalcemic PHPT patients.