An intrauterine device (IUD) is a small, T-shaped piece of flexible plastic placed inside the uterus as a form of long-acting reversible contraception. IUDs are highly effective and categorized as either hormonal or non-hormonal. An ovarian cyst is a common, fluid-filled sac that develops on or within an ovary. Many people question whether IUD use influences cyst formation, so this article explores the association between IUD types and their physiological effects on the menstrual cycle.
Understanding Ovarian Cysts
Ovarian cysts are common and often develop as a normal part of the menstrual cycle, known as functional cysts. These form when a follicle, the sac that holds a developing egg, does not behave as expected. A follicular cyst occurs if the follicle fails to rupture and release the egg, continuing to grow with fluid inside. A corpus luteum cyst forms if the follicle releases the egg but then seals up and retains fluid instead of dissolving.
Functional cysts are typically benign and produce no symptoms. They are transient structures, usually resolving on their own within one to three menstrual cycles without medical intervention. Cysts not related to the normal cycle are called pathological cysts, arising from abnormal cell growth. Functional cysts are the type most frequently associated with contraceptive use.
The Link: Hormonal IUDs and Functional Cysts
Hormonal IUDs (e.g., Mirena, Kyleena, Liletta, Skyla) release the synthetic progestin levonorgestrel into the uterus. This hormone primarily prevents pregnancy by thickening cervical mucus and thinning the uterine lining. The progestin also introduces subtle disturbances in the ovarian function of some users.
The hormone partially suppresses the hypothalamic-pituitary-ovarian axis, the signaling pathway between the brain and ovaries. While this suppression is usually not strong enough to stop ovulation completely, it can interfere with the final step: the rupture of the mature follicle. This interference causes the follicle to continue growing and retaining fluid, resulting in a functional ovarian cyst.
Clinical trials confirm that functional cysts occur in a percentage of hormonal IUD users. Reported rates vary significantly; for example, some devices show up to 22% of users developing a cyst in the first year. Other data indicates prevalence between 1.1% and 2.4% over three years. The vast majority of these cysts are small, measuring less than five centimeters, and are usually self-resolving, requiring only watchful waiting from a healthcare provider.
Copper IUDs and Cyst Formation
The non-hormonal copper IUD (e.g., Paragard) operates through a mechanism that does not involve the ovarian cycle. It prevents pregnancy primarily by causing a localized inflammatory reaction within the uterus that is toxic to sperm. Since the copper IUD does not release hormones, it does not interfere with the natural rise and fall of ovarian hormones.
Because of its non-hormonal action, the copper IUD does not alter ovulation or follicular rupture. Users have a risk of functional ovarian cysts similar to those who use no contraception. The prevalence of cysts in copper IUD users is typically low, with reported rates between 1.2% and 2.1%.
Recognizing Symptoms and Seeking Medical Advice
Most functional ovarian cysts are asymptomatic, but some may cause noticeable symptoms. These include a dull ache or pressure in the lower abdomen, often localized to one side. Bloating and a feeling of fullness are also common, resulting from pressure on surrounding structures. While these mild symptoms do not require emergency intervention, they should prompt a conversation with a healthcare provider.
Immediate medical attention is necessary if symptoms are sudden and severe, indicating a complication. Signs of a ruptured cyst include acute, sharp pain, sometimes accompanied by nausea or vomiting. Ovarian torsion, where the ovary twists on its blood supply, causes excruciating, sudden pain and is a surgical emergency.
A healthcare provider typically uses a transvaginal ultrasound to diagnose the cyst, confirming its size and fluid content. Management for a suspected functional cyst is usually watchful waiting, as 94% resolve spontaneously within six months. The presence of a cyst while using a hormonal IUD rarely necessitates device removal, as it is a temporary and expected side effect of the progestin.