Combined effects of the variants FSHB -211G>T and FSHR 2039A>G on male reproductive parameters.

CONTEXT

A polymorphism in the FSHB promoter (-211G>T, rs10835638) was shown to influence male serum FSH levels, whereas a polymorphism in the FSH receptor gene (FSHR; 2039A>G, rs6166) was previously shown to be associated with FSH levels in women only.

OBJECTIVE

The objective of the study was to analyze the effects of both FSHB -211G>T and FSHR 2039A>G on male reproductive parameters.

DESIGN AND SETTING

A total of 1213 German men attending an infertility clinic were genotyped by TaqMan assay.

PATIENTS

Patients included male partners in infertile couples without known causes for male infertility.

MAIN OUTCOME MEASURES

An association analysis of single and combined single-nucleotide polymorphism genotypes with clinical parameters was performed.

RESULTS

The FSHB -211G>T T-allele showed significant dosage effects for FSH (-0.51 U/liter per T-allele), LH (0.28 U/liter), and bitesticular volume (-3.2 ml). Statistical significance was enhanced severalfold after a meta-analysis comprising 3017 men. TT carriers were significantly more prevalent among men with lower sperm counts. The FSHR 2039A>G G-allele exhibited nonsignificant trends for associations with higher FSH and reduced testicular volumes. However, in the combined model, FSHR 2039A>G significantly modulated the more dominant effect of FSHB -211G>T on serum FSH and testicular volume among the T-allele carriers.

CONCLUSIONS

By analyzing both single-nucleotide polymorphisms for the first time, we convincingly show that indeed FSHR 2039A>G has an effect also in males. In the proposed model of the combined effects, FSHB -211G>T acts strongly on male reproductive parameters, whereas the FSHR 2039A>G effects were approximately 2-3 times smaller. Clinically this is of importance because oligozoospermic patients carrying unfavorable variants affecting FSH action may benefit from FSH treatment.