Are regular periods on Tamoxifen bad?

Hi, Kika. I was also diagnosed when premenopausal, and I will try to share some things I learned about tamoxifen. First, it works by fitting in the estrogen receptor on cancer (that may or may not be present) so it can't "feed" on real estrogen. So tamoxifen is not designed to stop your hormone cycle and your periods. One good thing about having periods is that it is thought to negate tamoxifen's very small risk of endometrial cancer because the uterus is getting "cleared out". Second, while tamoxifen can mess with your periods and your hormones, periods are not a reliable indicator of whether tamoxifen is working, or of your hormonal status when you are on tamoxifen. To check your hormonal status you can have a blood test to check your estradiol. That would give the doctors an idea of whether your levels are in normal premenopausal range, or abnormally high, or low enough to suggest you are heading toward menopause. Your gynecologist could order and interpret this test. But what would your doctors do with the information? If your levels are normal or low, that might reassure you. If your levels are abnormally high (as in my case with no periods), would they and you consider ovarian suppression or oophorectomy along with the tamoxifen or an aromatase inhibitor? What would be the risks vs. benefits?

I don't like hearing that your onc is so uninterested and does not answer your questions adequately. I had one of those and I fired him. If your onc is not concerned, she needs to explain why so you can feel reassured. She needs to remember that low risk does not mean no risk, and that you deserve to have your concerns addressed. It is your body and your health, including your mental health. Our mental health does not benefit from worry and stress that a caring doctor could help alleviate.