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Frequency of the calcium-sensing receptor variant A986S in patients with primary hyperparathyroidism.

OBJECTIVE
Recent studies have shown an influence of the calcium-sensing receptor variant A986S on the serum calcium concentration, suggesting that this genetic variant could be a candidate for various bone and mineral disorders. The intention of this study was therefore to investigate the frequency of the described calcium-sensing receptor variants A986S, R990G and Q1011E in patients with primary hyperparathyroidism to test the hypothesis as to whether these variants represent risk factors for the development of primary hyperparathyroidism.


DESIGN
Fifty patients with primary hyperparathyroidism were included in the study. One hundred and two healthy blood donors served as controls.


METHODS
Detection of the genetic variants A986S, R990G and Q1011E was done by direct sequencing of exon 7 of the calcium-sensing receptor in leucocyte DNA.


RESULTS
The heterozygous variant A986S was found in 34% (17 of 50) of the healthy age- and sex-matched controls and 40% (20 of 50) of the patients with primary hyperparathyroidism. This difference was not statistically significant (P=0.68). However, in male patients the heterozygous variant A986S was found more frequently (67%, 6 of 9) than in male controls (20%, 2 of 10, P=0.07). The variants R990G and Q1011E were found less frequently (8-20%) in patients and controls without significant differences between the groups. Patients with the heterozygous variant Q1011E had significantly higher serum calcium and parathyroid hormone levels than patients with the wild-type variant (P<0.01). There was no correlation of serum calcium (total and corrected for albumin) with the calcium sensing receptor variant A986S in 102 healthy blood donors (P=0.45).


CONCLUSIONS
The calcium-sensing receptor variants do not, therefore, seem to be major genetic determinants for the development of primary hyperparathyroidism. The variant A986S may possibly represent a risk factor for the development of parathyroid neoplasia in men. Moreover, the presence of the genotype Q1011E might influence the clinical course of the disease. The previously reported significant correlation of serum calcium levels with the genetic variant A986S in healthy subjects could not be confirmed.