Tamoxifen Side Effects/Fingernails.

Vaginal discharge is a common, well-documented side effect of tamoxifen due to its estrogen-like effects on the uterus, while brittle/weak nails, although less commonly discussed, are recognized as a potential, less common side effect, often linked to changes in hormone levels. These occur because tamoxifen acts as an estrogen blocker in some tissues (like breast) but an activator in others (like the uterus), influencing cell growth and tissue hydration.
Tamoxifen causes broad anti-estrogen effects, which can result in overall, systemic reduction in moisture and changes to collagen and protein production in skin, hair, and nails.
My sister takes tamoxifen and has experienced similar changes.

On 20 mg of tamoxifen I had weaker nails, on 5 mg they are fine. I agree with @kathleen1314 that its an estrogen, collagen thing.
I also have a vaginal discharge, but there is very little with the 5 mg dose. I have not had any issues with irritation or infections. But I have just started a vaginal tablet moisturizer containing hyaluronic acid because the thinner skin in the vagina/vaginal wall does get irritated during sex. My PCP recommended the brand Revaree by Bonifide, non-prescription, but there are other available brands.

I started Tam Jan. 1st & I am taking a half-dose (10 mg) which might make a difference. Haven't noticed changes in my nails, only an occasional mild headache & some "warm" flashes! Interesting how we all have different reactions.

@cynthiaofstedal hello and welcome to connect. These are all pretty common complaints with anti-estrogen therapy, and even more shocking if you had not already entered menopause.
I found both of these things to be true although since nails are dead tissue and only grow so fast I did not have nail changes that fast from anti estrogen therapy. However, I had very fast changes with the nail bed from pretty much every cancer treatment I have had including anti estrogen treatments. My solution has unfortunately became over time to keep my nails very short so that I don’t break them lengthwise creating pain.
Have you had any other systemic cancer treatments? Could this be a change to the nail bed, creating a weak nail?

@auntieoakley I too have experienced soft nails. Solution is just keep them short and file often💕