Background: There are two known polymorphisms of clinical relevance in the follicle-stimulating hormone (FSH) receptor exon 10, alanine or threonine at position 307, and asparagine or serine at position 680, giving rise to two discrete allelic variants: Thr307/Asn680 and Ala307/Ser680. At position 680, three FSH receptor variants are possible: Asn/Asn, Asn/Ser, and Ser/Ser. We hypothesized an association between FSH receptor polymorphisms and ovarian reserve.
Methods: FSH receptor polymorphisms at position 680 were studied in a population of 68 infertile women. We used serum FSH level at cycle day 3 as a screening for ovarian reserve. DNA was extracted from peripheral leukocytes in whole blood by using PCR and DNA sequencing in order to determine the type of FSH receptor.
Results: The distribution of FSH receptor variants was Asn/Asn (AA) 35%, Asn/Ser (AS) 24%, and Ser/Ser (SS) 41%. In women with normal ovarian reserve, FSH levels at cycle day 3 were 5.6 +/- 1.9 (AA group), 6.7 +/- 1.3 (AS group), and 5.7 +/- 1.7 (SS group) (non-significant). Corresponding FSH levels at cycle day 10 were 6.9 +/- 1.9, 6.3 +/- 1.7, and 8.3 +/- 2.8 (P < 0.01, AA and AS vs. SS group). In the SS group, FSH levels at cycle day 10 were significantly higher than they were at cycle day 3 (P < 0.05).
Conclusions: The results show that Ser/Ser-680 predominates in the studied infertile population. Furthermore, women with normal ovarian reserve and the Ser/Ser FSH receptor variant had significantly higher FSH levels, compared to women with Asn/Asn and Asn/Ser variants. FSH receptor genotyping may, thus, be interesting as an adjunct indicator of ovarian reserve for infertile women undergoing assisted reproduction, and may be helpful in the determination of the starting dosage of FSH in in vitro fertilization.