Estrogen levels in aging women are highly variable.
After menopause the ovaries continue to atrophy and eventually stop producing estrogen altogether.
As you have been told, estrogen is then produced by fatty tissue (adipose synthesis of estrone (E1)).
However, this capacity is variable.
In some women, fatty tissue synthesis can compensate well enough till a very old age, maintaining a steady level. But in other women, this is not so and estrogen continues to decline.
Hence there is a wide variability of estrogen in elderly women, with some continuing to maintain at 100 pmol but in most women it falls further than that with advancing age.
Hope I have been able to clarify the situation for you and helped in resolving your query.
If you need more help, please let me know so l can continue to assist you.
Thank you and I wish you the best of health - stay safe!
Dr. P. Jyoti