Copper toxicity associated with intrauterine devices
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Copper Toxicity and Systemic Safety in Copper Intrauterine Device (Cu-IUD) Users
Multiple studies have examined whether copper intrauterine devices (Cu-IUDs) cause copper toxicity in users. Research in both animal models and human populations consistently shows that Cu-IUDs do not lead to significant increases in blood copper levels or systemic copper toxicity, even with long-term use or at doses much higher than those used clinically. In animal studies, rats implanted with Cu-IUDs at up to 60 times the clinical dosage for the equivalent of over 15 years in humans showed no signs of systemic or local organ toxicity, and their liver and kidney functions remained normal throughout the study period . Similarly, in human studies, women using Cu-IUDs for various durations did not have higher blood copper levels or more symptoms of copper toxicity compared to non-users, and no clinically significant adverse effects were observed Atef2024Crandell2021Prema1980+1 MORE.
Blood Copper Levels and Clinical Symptoms in Cu-IUD Users
A review of several studies found that most did not detect an increase in blood copper levels among Cu-IUD users, while a few reported small increases. However, all studies measured total copper rather than the free copper form, which is more relevant to toxicity, making the clinical significance of these findings uncertain . In a recent cross-sectional study, no differences in blood copper levels or copper toxicity symptoms were found between long-term Cu-IUD users, short-term users, and non-users, supporting the safety of these devices . Additionally, urinary copper excretion was similar between users and non-users, suggesting that copper released from the device is not readily absorbed systemically .
Local Effects and Side Effects: Inflammation and Bleeding
While systemic toxicity is not a concern, local side effects such as abnormal uterine bleeding and inflammation are more common. The initial "burst release" of copper ions after device insertion can cause local tissue irritation, leading to side effects like bleeding and pain, which typically decrease over time as copper release stabilizes Fan2021Bastidas2019Yang2024. Research into the molecular mechanisms has shown that copper ions can alter the expression of certain microRNAs in the endometrium, contributing to local tissue injury and abnormal bleeding . However, these effects are generally limited to the uterus and do not indicate systemic copper toxicity.
Innovations to Reduce Local Copper Toxicity
To address local side effects, new materials and alloys for Cu-IUDs are being developed. Alloys such as ultra-fine-grained copper-magnesium (Cu-0.4Mg) and copper-iron (Cu-5Fe) have been shown to reduce the initial burst release of copper ions, improve biocompatibility, and decrease local tissue inflammation, while maintaining contraceptive effectiveness Fan2021Yang2024. These innovations may further reduce the risk of local adverse effects without increasing systemic copper exposure.
Conclusion
Current evidence strongly supports the systemic safety of copper intrauterine devices, with no significant risk of copper toxicity in users, even with long-term use. Blood copper levels remain within normal ranges, and systemic symptoms of copper toxicity are not observed. Local side effects, such as bleeding and inflammation, are more common but are being addressed through advances in device materials. Overall, Cu-IUDs remain a safe and effective contraceptive option for most women.
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