Serum parathyroid hormone levels are associated with FokI polymorphism of the vitamin D receptor gene in untreated postmenopausal women.

Background: Allelic variants in polymorphisms of the vitamin D receptor (VDR) gene have been related to the incidence of secondary, as well as primary, hyperparathyroidism. In spite of their pathophysiological importance, the relationships between VDR genotypes and serum PTH regulation in normal women have not been extensively investigated.

Methods: We studied the association between the VDR gene (FokI polymorphism) and serum parathyroid hormone (PTH) levels during the winter in 95 untreated, postmenopausal women with normal values of serum PTH. We checked statistically for years since menopause (YSM) and serum ionized calcium. Intergroup differences in serum PTH levels between FF, Ff, and ff allele combinations of FokI polymorphism were evaluated using a one-way ANCOVA and the least significant difference (LSD) multiple comparisons test.

Results: Significant intergroup differences were found in PTH values (P<0.035, ANCOVA), which were higher in the ff than in the FF genotype (P<0.01, LSD). No differences in serum PTH were found between allele combinations in ApaI, TaqI, and BsmI polymorphisms.

Conclusion: Our findings suggest that the FokI polymorphism of the VDR gene is closely related to the magnitude of PTH secretion and/or degradation in postmenopausal women. The causal importance of this phenomenon in the development of postmenopausal osteoporosis remains to be determined.