Endocrine Abstracts

Background: Primary hyperparathyroidism (PHPT) is a common endocrine disorder accompanied by high cytokines and low total 25-hydroxyvitamin D [25(OH)D]. An inflammatory cytokine, monocyte chemoattractant protein-1 (MCP-1), is found to be higher in people with elevated parathyroid hormone (PTH), unlike other cytokines (1). Also, a rise in MCP-1 in response to high PTH is associated with bone loss (2). Parathyroidectomy (PTX) is the only cure for patients with PHPT. Whether the decline in PTH due to PTX leads to a decrease in MCP-1 and its effect on vitamin D metabolites remains unclear.

Objective: To investigate the effect of PTX on serum MCP-1 and vitamin D metabolites in patients with PHPT.

Methods: Patients with PHPT who underwent minimally invasive PTX were included. Serum samples were collected before and 3-month after surgery. Serum levels of calcium, PTH, vitamin D binding protein (DBP), total and free 25(OH)D, MCP-1, and C-reactive protein (CRP) were measured. Correlation coefficients and multiple linear regression models were used to assess relationships among PTH, vitamin D metabolites and cytokines.

Results: In 25 PHPT patients (age: 61±11 years old; BMI: 31.0±5.6 kg/m² ), levels of serum PTH and calcium were decreased (PTH: 118.6±42.4 to 44.7±25.2 pg/ml; Ca: 11.0±0.6 to 9.6±0.4 mg/dL; P<0.001) to normal after PTX. Meanwhile, both total and free 25(OH)D were significantly increased (28.1±10.2 to 37.9±11.2 ng/ml; 4.9±2.1 to 8.1±3.8 pg/ml; P<0.001), together with elevated DBP (P<0.001) after surgery. The level of MCP-1 declined by 20% (P<0.001), while CRP remained relatively stable after PTX. The PTH was negatively correlated with total and free 25(OH)D, and DBP (P<0.01), however, positively correlated with MCP-1 (P<0.01). The CRP (but not MCP-1) was found to be negatively correlated with both total and free 25(OH)D (P<0.01).

Conclusion: These data show that the decline of PTH due to PTX down-regulates serum MCP-1, but not CRP. Also, PTX normalizes PTH and Ca level, and leads to an increase in DBP, total and free 25(OH)D, which appears to be independent of MCP-1. The role of MCP-1 on PTH, total and free 25(OH)D and bone in patients with PHPT remains unclear and further studies are needed.

References: 1. Sukumar et al. (2011). The high serum monocyte chemoattractant protein-1 in obesity is influenced by high parathyroid hormone and not adiposity. JCEM. doi:10.1210/jc.2010-2781.

2. Siddiqui et al. (2017). Catabolic Effects of Human PTH (1-34) on Bone: Requirement of monocyte chemoattractant protein-1 in Murine Model of Hyperparathyroidism. Sci. Rep. doi:10.1038/s41598-017-15563-7.