Both may slow weight loss.
Or aka "increase metabolic resistance" , almost any hormone med according to Jackie Eberstein. On this list
http://forum.lowcarber.org/showthread.php?t=453311
I spoke with her personally when I was on Tamoxifen.
In Dr Westman's new talk on DietDoctor, he also mentions weight loss is slower/harder the older you are, the less active, and for women, the farther into menopause.
https://www.dietdoctor.com/day-low-carb-clinic
So nothing to do about age
...but add more activity, be strict about carbs and calories (Jackie suggested cutting out all nuts, wine and cheese, limit added fats)
Personally I am not a fan of HRT, and wishing you good results from natural treatment, or the shortest course of the lowest dose, to get through the transition.