It is traditionally taught that estrogen is produced by the granulosa cells of the follicle. But before menarche, where does the estrogen come from? Is it from the thin layer of granulosa cells lining the primordial follicles? The adrenal zona reticularis produces androgens physiologically. Are they converted to estrogen? If yes, by whom? If not by the ovary, would the levels of estrogens be same in prepubertal boys and girls?
More importantly, are there estrogens in a girl before menarche? If yes wouldn't they cause endometrial changes?