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

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 R = 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 R = 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.