LOVE that JohnsHopkins ask an expert site....I asked the question and it was answered within a few minutes:
I was on tamoxifen from 6/2000 until 6/2005, from age 31.5 to age 36.5. My periods were pretty regular for all 5 years. My first 2 periods after tamoxifen have been much heavier than they used to be. Is this normal? And if so, can I typically expect them to become lighter after a couple of months, or will it be heavy for the duration? I am seeing my GYN next week for a routine check, but wondered from your perspective. Thank you.
its not unusual for the lining of the uterus to thicken as a side effect of tamoxifen. it now is able to rid itself of that additional lining with menstruation. your gyn will evaluate you to let you know how long to anticipate this happening. congrats on being done!
Here is the link: