Objective:To investigate the association of a (CA)n dinucleotide repeat polymorphism of ERβ with unknown aetiology hypomenorrhea. Methods:We choosed 100 eumenorrhea women as control group and another 100 hypomenorrhea patients as case group from Southwestern China. At the same time

we bring depuration

clone and sequence analysis to CA repeat polymorphism in 5 intron region of estrogen receptor β to illuminate its repeated sequence polymorphism distributing between control and case group and its relationship with unknown aetieological hypomenorrhea. Results:We got 9 alleles and the repeated number of (CA) n was 16～24. There was not difference between distributing frequencies of CA repeat polymorphism in control and case groups(χ2=7.155

P=0.520). SS genotype was defined as repeat number n≤20

LL for n>20. Case group SS genotype rate was 66%

control group 51%

OR=1.865(95%CI:1.055～3.298).The SS and LL allele genotypes frequency was compared in two groups and the difference was significant(χ2=4.634

P=0.031). Conclusion:ERβ gene CA repeat polymorphism is related to unknown aetiological hypomenorrhea. SS allele genotype may be the risk factor of unknown aetiological hypomenorrhea.