What causes breast pain after inserting a Mirena IUD?

　　Breast pain after inserting the Mirena IUD may be related to side effects, or it could be due to pre-existing conditions such as mammary gland hyperplasia or breast fibroadenoma. Insertion of the Mirena IUD may exacerbate these underlying conditions, leading to breast and nipple pain. Patients are advised to seek medical attention promptly and undergo appropriate examinations followed by symptomatic treatment.

　　1. Side Effects

　　The Mirena IUD is a hormonal intrauterine device that releases levonorgestrel. After insertion, the device releases progesterone within the uterine cavity, which can stimulate the development of mammary gland alveoli, causing breast congestion, swelling, and pain, including nipple tenderness.

　　2. Mammary Gland Hyperplasia

　　In patients who already have mammary gland hyperplasia, the release of progesterone from the Mirena IUD may further promote alveolar proliferation, worsening existing breast symptoms and resulting in noticeable breast swelling and nipple pain.

　　3. Breast Fibroadenoma

　　For patients with breast fibroadenoma, the progesterone released by the Mirena IUD inside the uterine cavity may further stimulate excessive proliferation of breast cells, causing the fibroadenoma to enlarge and compress nerves or surrounding tissues, thereby leading to breast swelling and nipple pain.

　　Besides the above causes, breast cancer may also present similar symptoms. Therefore, patients are strongly advised to seek early medical evaluation and timely treatment.