amenorrhea following treatment with tamoxifen

I took tamoxifen for four years for breast cancer prophlyaxis but had to discontinue treatment due to development of cataracts.  I menstruated regularly while taking tamoxifen but have not had a period since stopping it.  I understand this sometimes happens with tamoxifen.  Can you explain why?

[CCF-RN,MSN-rf]

Dear wuhanmom:  Tamoxifen is a SERM (selective estrogen receptor modulator) which, oversimplified, means that it blocks estrogen from the breast tissue but may actually provide increased estrogen to other areas such as the ovaries.  This may be a possible explanation. It may be worth while to have a gyn examiniation.  If this is of concern, your ovarian function could be checked to see "where you are" in terms of ovarian function.