Effect of Parathyroidectomy on Bone Turnover Markers and BMD of Symptomatic and Asymptomatic Patients with Primary Hyperparathyroidism: Prospective Follow Up Study from a Tertiary Care Center in North India

Introduction: Data regarding the effect of parathyroidectomy on bone turnover markers and bone mineral density (BMD) in primary hyperparathyroidism (PHPT) are scarce. Moreover, the molecular mechanisms underlying PHPT phenotypic heterogeneity are not known.

Aims & objectives: Primary objective was to study the effect of parathyroidectomy on BMD and serum collagen C-telopeptide (CTx) in patients with PHPT. Secondary objective was to explore the underlying molecular mechanisms in the pathogenesis of symptomatic and asymptomatic sporadic PHPT.

Methods:

Material and methods: A prospective follow-up study conducted at a tertiary care centre in North India. Consecutive patients with PHPT undergoing parathyroidectomy were included in the study. All biochemical parameters, Serum CTx and BMD at hip, forearm and lumbar spine (with DXA scan, GE Lunar) were evaluated at baseline and again at 3 months post parathyroidectomy. The mRNA expression of vitamin D receptor (VDR), calcium sensing receptor (CASR), cyclin D 1 (CD1), and parathyroid hormone (PTH) in parathyroid adenoma cells and controls was determined using quantitative real-time PCR (qRT-PCR). Study was approved by institutional ethics committee.

Results:

Total of 84 patients underwent parathyroidectomy. Following exclusion of 6 patients, 78 (M = 31, F= 47) were included in the final analysis. Mean±SD age was 50.36 ± 14.83 years. 34 patients (43.5%) were asymptomatic. Mean±SD serum CTx level at baseline was 829.83±696.85 pg/ml which reduced significantly 3 months post-surgery (320.1±293.8). Significant decline in S.CTx levels was seen in both symptomatic and asymptomatic group. Similarly, serum calcium, iPTH, and urine calcium-creatinine ratio were significantly lower at 3 months post-surgery as compared to pre-surgery level. The proportion of osteoporosis and osteopenia at baseline among study participants were 50% and 37.14% respectively. BMD gain at 3 months was statistically significant at lumbar spine (0.98 ± 0.21 to 1.04 ± 0.21, p = 0.007) but not at left femur (0.85 ± 0.16 to 0.89 ± 0.16, p = 0.064) and forearm (0.65 ± 0.16 to 0.67 ± 0.17, p = 0.416). Symptomatic PHPT group had significantly higher expression of PTH and CD1 mRNA compared with asymptomatic PHPT group.

Discussion/Conclusion:

A significant decline in Serum CTx levels and gain in BMD at lumbar spine was seen as early as 3 months post parathyroidectomy in both symptomatic and asymptomatic PHPT patients. This study also addressed for the first time, the molecular mechanisms underlying PHPT phenotypic heterogeneity. Asymptomatic PHPT had significantly lower expression of CD1 mRNA and PTH mRNA compared with symptomatic PHPT patients.