Effect of parathyroidectomy on osteopontin and undercarboxylated osteocalcin in patients with primary hyperparathyroidism

ABSTRACT

Purpose: Surgical treatment for primary hyperparathyroidism (PHPT) improves bone metabolism. Osteocalcin (OC) and its undercarboxylated form (ucOC) are associated with bone and energy metabolism. Osteopontin (OPN), a multifunctional protein expressed in bone, is involved in resorption, along with β-carboxyl-terminal cross-linking telopeptide of type 1 collagen (β-CTX), and osteoprotegerin (OPG). Our aim was to investigate these biomarkers of bone metabolism in patients with PHPT. Methods: We examined 30 individuals with PHPT, in a clinical research facility, before and 1 month following parathyroidectomy. Circulating levels of OC, ucOC, OPN, β-CTX, and OPG were examined as bone biomarkers along with inflammatory markers (e.g., interleukin-6 [IL-6], lipocalin-2), insulin resistance (i.e., homeostasis model assessment for insulin resistance [HOMA-IR]), adiposity (i.e., leptin, adiponectin), PTH, calcium, 25-hydroxyvitamin D, creatinine, and demographics. Results: Participants (27 females/3 males) were 60 ± 9 (mean±SD) years old. There was a significant reduction of ucOC (7.9 ± 5.1 [median±SIQR] vs. 6.6 ± 3.7 ng/mL, p = 0.022) and OPN (75.4 ± 14.5 vs. 54.5 ± 9.2 ng/mL, p < 0.001) pre- versus post-parathyroidectomy. There were no univariate differences postoperatively for IL-6, HOMA-IR, leptin, or adiponectin. Regression analysis showed that postoperative levels of adiponectin, IL-6, and OPN were significantly associated with ucOC, while adjusting for PTH and albumin corrected calcium levels (model R² = 0.610, p = 0.001). With OPN as the dependent variable, higher adiponectin and lower ucOC were significantly associated with lower OPN levels postoperatively (model R² = 0.505, p = 0.010). Conclusion: The lower 1-month postoperative OPN and ucOC levels in PHPT seem to indicate reduced bone resorption. Decreased ucOC levels may also suggest lower energy demands postoperatively.

KEYWORDS:

• Osteopontin
• parathyroidectomy
• primary hyperparathyroidism
• undercarboxylated osteocalcin

Acknowledgments

The authors thank members of the Department of Nuclear Medicine, Christiana Care Health System, Newark, DE, USA, for their help in recruiting participants for this study.

Funding

This work was supported by the Clinical Research Committee, Department of Medicine, Christiana Care Health System, Newark, DE, USA. The statistical analysis only was partially supported by an Institutional Development Award (IDeA) from the National Institute of General Medical Sciences of the National Institutes of Health under grant number U54-GM104941.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Additional information

Funding

This work was supported by the Clinical Research Committee, Department of Medicine, Christiana Care Health System, Newark, DE, USA. The statistical analysis only was partially supported by an Institutional Development Award (IDeA) from the National Institute of General Medical Sciences of the National Institutes of Health under grant number U54-GM104941.