The vitamin D receptor fokI start codon polymorphism and bone mineral density in male hypogonadotrophic hypogonadism

The genetic factors determining bone mineral density (BMD) are not well characterized. Many studies have investigated the relationship between the fokI polymorphism of vitamin D receptor (VDR) gene in diverse populations and gender, resulting in conflicting outcomes. Because peak bone mass in men is closely related to sufficient androgen release, the contribution of VDR gene on BMD might have been masked by hormonal status of adulthood. We therefore investigated the relationship between the fokI polymorphism of VDR and BMD in male patients with idiopathic hypogonadotrophic hypogonadism (IHH). Sixty-five untreated male patients with IHH and 39 healthy matched controls were evaluated. fokI polymorphism ("f" allele) was detected by polymerase chain reaction (PCR)-restriction fragment length polymorphism using restriction endonuclease fokI, and BMD was measured by dual Energy X-ray absorpsiometry in lumbar spine, femur and radius. The distribution of FF, Ff, and ff alleles in patients with IHH and controls were not different (patients; 46%, 51%, 3% and controls; 51.3%, 46.1%, 2.6%, respectively). BMD levels in patients with IHH were significantly lower than controls. We categorized patients and control subjects in subgroups according to whether they had homozygous FF and heterozygous Ff genotype. No differences in BMD were seen between control subgroups, but total femur and femoral neck BMD were significantly lower in patients bearing heterozygous Ff genotype with IHH than homozygous FF ones (p=0.017 and p=0.009, respectively). Ff genotype might run down the BMD in cortical bone of femur, which needs to be proved in further studies.