CO-EXISTING HASHIMOTO'S THYROIDITIS DOES NOT AFFECT BONE METABOLISM IN PATIENTS WITH PRIMARY HYPERPARATHYROIDISM.

CONTEXT: Primary hyperparathyroidism (PHPT) is often associated with thyroid disorders like nodular goiter, Hashimoto's thyroiditis (HT) and Graves' disease.

OBJECTIVE: Our aim was to explore whether the co-existence with HT affects bone metabolism in patients with PHPT.

DESIGN: This was a comparative cross-sectional study carried out in a tertiary inpatient endocrine center from January 2018 through December 2020.

SUBJECTS AND METHODS: A total of 234 patients were diagnosed with PHPT at our endocrine center. One hundred of them were included in the study - 50 with PHPT only and 50 with PHPT and HT. Two control groups were defined: 37 with HT and 37 without PHPT and HT. Serum markers of calcium-phosphate metabolism, bone markers (RANKL, Osteoprotegerin, β-CTX, Osteocalcin) and interleukin-17A were measured.

RESULTS: The frequency of HT among patients with PHPT was 37.6% (95% CI 31-43%) and did not differ significantly from that in the general population, 32.5% (95% CI 30-35%). Age, BMI, markers of calcium-phosphate metabolism, bone markers and interleukin-17A weren't significantly different in PHPT with and without HT or between the two control groups. The participants with PHPT had higher levels of interleukin-17A, β-CTX and Osteocalcin (p<0.05) than those without the PHPT. RANKL and Osteoprotegerin in these groups did not differ.Interleukin-17A correlated positively with serum calcium, PTH and RANKL and negatively with serum inorganic phosphate and 25(OH)D. Controlling for HT and age did not change the correlation.

CONCLUSIONS: In our study, HT has not additional effect on bone metabolism in the patients with PHPT. Higher levels of interleukin-17A in PHPT suggest a possible role in the PTH-induced bone remodeling.