Endocrine Abstracts

Objective: Normocalcemic primary hyperparathyroidism (PHPT) is a phenotype of PHPT characterized by normal serum calcium and persistently increased parathyroid hormone (PTH) after exclusion of secondary causes of PTH elevation.

The aim: of this study was to investigate the capability of the short test with active metabolites of vitamin D for differential diagnosis between normocalcemic PHPT and secondary hyperparathyroidism (SHPT) for inpatient treatment.

Material and methods: We included 90 hospitalized patients with normal albumin-adjusted calcium (Ca_adj.) and elevated PTH levels (84 women, 6 men, median age 60 years). Ca_adj, PTH, creatinine, eGFR, daily calciuria were evaluated before and PTH, Ca_adj., creatinine, eGFR 3–5 days after taking 1 mcg of alfacalcidol or calcitriol. Data is presented by medians and interquartile ranges (Median, (25;75)).

Results: According to baseline and dynamic biochemical evaluation patients were divided into 3 groups: group 1 (n=32) – patients with elevated or within the upper limit PTH (n=4) who reached hypercalcemia (Ca_adj.> 2.55 mmol/l); group 2 (n=14) – patients with normalization of PTH and normal Ca_adj; group 3 (n=44) patients with elevated PTH and normal Ca_adj.. In group 1, baseline Ca_adj. was 2.52 mmol/l (2.50; 2.54), PTH 101.1 pg/ml (81.9; 138.0), after short test – 2.61 mmol/l (2.58; 2.64), and 92.3 pg/ml (71.2; 119.5) respectively, regarded as PHPT. Among them 19 patients underwent surgery with histological confirmation of diagnosis, 2 patients are waiting for surgery, 11 patients with asymptomatic form are under dynamic observation. In group 2, baseline Ca_adj. was 2.34 mmol/l (2.31; 2.44), PTH 81.1 pg /ml (72.9; 95.7) vs 2.40 mmol/l (2.33; 2.51) and 54.53 pg/ml (40.7; 63.6) respectively after short test regarded as SHPT. Groups with PHPT and SHPT significantly differed from each other in Ca_adj and daily calciuria (P<0.05) but not in PTH, eGFR. 44 patients from group 3 did not show significant changes thus differential diagnosis was continued on an outpatient basis.

Conclusion: The study showed significant changes in calcium and PTH levels during the short test in 46/90 patients. Stable normocalcemia and normalization of PTH allows confirming SHPT while elevated or within the upper limit PTH levels with hypercalcemia – PHPT.