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How Does Mirena Work for Fibroids?

Uterine fibroids, also called leiomyomas or myomas, are noncancerous growths that form in the uterus. Fibroids can range in shape and size and symptoms vary greatly. Many women never realize they have fibroids or their physicians discover them accidentally during a routine examination. However, some women require treatments and one such treatment is the use of levonorgestrel, or Mirena.


The National Institutes of Health explains that uterine fibroids are the most common type of tumor found in the pelvis and that as many as one in five women of childbearing years may have uterine fibroids 1. The cause of uterine fibroids is unknown, but the growth of the tumors seems to depend largely on the hormone estrogen. As long as a woman is menstruating, the fibroid will likely continue to keep growing, though usually slowly.


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Uterine fibroids develop in the muscle tissue of the uterus, according to the American Congress of Obstetricians and Gynecologists. The National Institutes of Health explains that uterine fibroids can be myometrial, occurring in the muscle of the uterine wall, submucosal, occurring just under the surface of the uterine lining, subserosal, occurring just under the outside covering of the uterus or pendunculated, protruding from a stalk on the outside of the uterus or inside the uterine cavity 1. Some fibroids are small, barely discernable within the uterus, while others can grow large enough to fill the pelvis or abdominal cavity. A woman may have one fibroid or multiple fibroids. The growth of uterine fibroids is unpredictable 1. Many fibroids may stay very small, while others grow rapidly or continue growing for a number of years.


Symptoms of uterine fibroids often include abdominal fullness, bleeding between periods, increased urinary frequency, heavy menstrual bleeding, menstrual periods that last longer than normal, feeling of pressure in the lower abdomen, pain during intercourse, pelvic cramping or painful periods. The American Congress of Obstetricians and Gynecologists explains that other symptoms may include enlarged uterus and abdomen, miscarriages and infertility.


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Mirena is an intrauterine device approved by the Food and Drug Administration for use as birth control as well as to help relieve heavy bleeding in women suffer from heavy bleeding and pain caused by uterine fibroids, according to 2. Mirena works by releasing a steady dose of progestin, a hormone that provides relief of symptoms, but does not shrink tumors.

Side Effects

Like all medications, Mirena has side effects. Common side effects include:

  • acne
  • back pain
  • breast pain
  • changes in menstrual bleeding
  • changes in sex drive
  • bleeding
  • cramping
  • headache
  • nausea
  • vomiting
  • weight gain
  • cramping during placement
  • according to 2

In rare cases, an allergic reaction may occur. Signs of an allergic reaction include

  • rash
  • hives
  • itching
  • breathing difficulties
  • chest tightness
  • swelling of the mouth
  • lips or tongue

Other severe reactions can include

  • genital sores
  • fever
  • breast lumps
  • vision changes
  • sudden leg pain
  • severe headache
  • vomiting
  • unusual vaginal discharge or odor
  • sudden crushing chest pain
  • painful sexual intercourse

Patients should alert their physician to these conditions immediately.