Increased levels of estradiol (E2) or estrone (E1) are seen in: Girls and Women: Early (precocious) puberty Tumors of the ovary or adrenal glands Boys and Men: Enlarged breasts (gynecomastia) Tumors of the testicles (testicular cancer) or adrenal glands [labtestsonline.org]

Estradiol or other hormone levels may be tested in the evaluation of precocious puberty in girls (the onset of signs of puberty before age seven), delayed puberty and in assisted reproductive technology (ART) to monitor ovarian follicle development in [healthywomen.org]

Side effects include: bloating breast soreness headaches leg cramps indigestion nausea vaginal bleeding fluid retention, leading to swelling Some types of hormone therapy can also increase the risk of a stroke, blood clots, and uterine and breast cancer [medicalnewstoday.com]