Heavily enlarged breasts may be related to factors such as heredity, obesity, pregnancy, medication, and macromastia. 1. Heredity: When adolescent women develop breast hypertrophy, it is often considered to be related to family genetic factors. If the mother and other close relatives have enlarged breasts, the chances of their children having enlarged breasts will increase. 2. Obesity: Studies have found that people with a body mass index greater than 30kg/m2 have a significantly higher chance of developing breast hypertrophy. Breast enlargement can be improved through weight control. 3. Pregnancy: During pregnancy, breast tissue is highly responsive to prolactin and progesterone stimulation, which can also lead to breast hypertrophy. 4. Drugs: Studies have found that after using drugs such as penicillinamide, cyclosporine, glucocorticoids, etc., adverse reactions to the drugs may occur, stimulating the proliferation of mammary tissues and leading to heavy breast hypertrophy. 5. Macromastia: Macromastia mostly occurs in puberty and pregnancy, the reason is still unclear, may be due to the breast tissue over-sensitivity to estrogen, can lead to breast hypertrophy. There may be other clinical causes of breast hypertrophy, so it is recommended to go to the breast surgery department of the hospital as soon as possible in order to clarify the cause of the disease.