Parathyroid Hormone Polymorphism RS6254 is Associated with the Development and Severity of Osteoporosis in Asymptomatic but not Normocalcemic Hyperthyroidism.

Although normocalcemic and asymptomatic hyperparathyroidism (HPT) are becoming more common, they remain only partially understood. Parathyroid hormone (PTH) polymorphisms have been associated with disease severity in classical HPT. The aim of the present study was to evaluate the clinical effect of PTH polymorphism (rs6254) in normocalcemic and asymptomatic HPT. A prospective study of 61 consecutive patients with normocalcemic or asymptomatic HPT was carried out. Secondary causes of HPT were ruled out. All patients were followed for≥1 year. Calcium and phosphorus metabolism parameters were assessed at least twice during the follow-up period to classify as normocalcemic or asymptomatic HPT. Bone mineral density (BMD) and the rs6254 polymorphism genotype were also assessed. Genotype rs6254GG was observed in 23 patients (37.7%) whereas GA and AA genotypes were presented in 29 (47.5%) and 9 (14.8%) patients, respectively. Age, sex and genotype distributions were comparable in both groups. In asymptomatic but not normocalcemic HPT patients, the GG genotype was associated with a significantly higher level of intact PTH [200.2 (SD 76.5) vs. 113.3 (SD 25.9) pg/ml; p<0.01], and significantly lower Z-score densitometry at the femoral neck, proximal femur, and lumbar spine. Both remained significant after adjusting for major confounding factors by multiple linear regression. The present study supports the independent pathogenic effect of rs6254GA polymorphism on the development and severity of BMD complications in patients with asymptomatic but not normocalcemic HPT. Further studies are needed to confirm this finding and to assess the effect of other polymorphisms in normocalcemic and asymptomatic HPT.

Clinical Expression of Calcium Sensing Receptor Polymorphism (A986S) in Normocalcemic and Asymptomatic Hyperparathyroidism.

Normocalcemic and asymptomatic hyperparathyroidism diagnosis are becoming more common. However, their pathophysiology is incompletely known. The aim of the present study was to evaluate the clinical effect of calcium-sensing receptor polymorphism (A986S) in normocalcemic and asymtomatic HPT. Prospective study conducted with 61 consecutive normocalcemic and asymptomatic HPT patients was followed up during a minimum period of 1 year. Secondary causes of hyperparathyroidism were ruled out. Calcium and phosphorus metabolism parameters were evaluated in at least 2 determinations during follow-up to classify as normocalcemic or asymptomatic hyperparathyroidism. Bone mineral density and A986S polymorphism genotype were also analyzed. Thiry-eight patients (62.3%) had the genotype A986A, and 23 (36.7%) patients had A986S (20 patients, 32.8%) or S986S (3 patients, 4.9%). Age, sex, and genotype distributions were comparable in both normocalcemic and asymptomatic hyperparathyroidism. In normocalcemic patients, S allele genotype was associated to statistically significant higher level of intact PTH: 92.0 (SD 18.5) vs. 110.6 (SD 24.4) pg/ml, p<0.05; and remained significant after adjustment by multiple linear regression. In asymptomatic hyperparathyroidism, A986A genotype resulted in a statistically significant higher level of intact PTH, alkaline phosphatase and procollagen amino-terminal propeptide; but only serum calcium remained as an independent predictor of serum intact PTH levels after a multiple linear regression. Bone mineral densitometry between genotypes did not show statistically significant differences. A986S polymorphism of CaSR is an independent predictor of PTH level in normocalcemic hyperparathyroidism patients, but not in asymptomatic hyperparathyroidism. More studies are needed to evaluate the effect of other polymorphisms in normocalcemic and asymptomatic hyperparathyroidism.