Role of copper in IUDs
Chantler, E.N.
Ippf Medical Bulletin 18(4): 1-2
1984
ISSN/ISBN: 0019-0357 PMID: 12266319 Document Number: 237575
This report analyzes the contraceptive potential of copper IUDs. The antifertility action of copper in IUDs is considered to involve 1) inhibition of zinc-containing metalloenzymes in the uterus, 2) reduced activity in the endometrial steroid receptor, 3) production of low levels of human chorionic gonadotropin in the luteal phase, 4) depression of ovum transport through the uterine tubes and inhibition of the penetration of cervical mucus by sperm, 5) elevation of the fibrinoloytic activity of the endometrium, and 6) depression of the synthesis of prostaglandins. These biochemical and physiological changes in response to copper released from the IUD are thought to cause only a local effect and systemic accumulation of copper from the device is considered unlikely. The rate of release of copper varies during the time the device remains in the uterus, declining exponentially during the 1st 2 years of use and then increasing as a result of destabilization and fragmentation of the accumulated layer of copper corrosion products. Accelerated copper loss is associated with menorrhagis, higher parity, and the presence of a cervical lesion at the time of IUD insertion. However, accelerated loss of the copper coil does not seem to cause either copper toxicity or decreased contraceptive efficiency. Women with insulin-dependent diabetes may manifest a different copper corrosion process and possibly a higher incidence of contraceptive failure. Since copper IUDs must be replaced more often than inert devices, there is a risk of increased incidence of pelvic inflammatory disease, reported to occur more frequently after replacement of an IUD. The longterm retention of copper IUDs probably has the same risk of infection as that associated with inert devices, and there is no evidence to link the presence of copper with any bacteriostatic or bactericidal action in vivo. The probability of fragmentation is reduced by new types of devices in which the copper wire is replaced by copper bands or a core of an inert metal is included inside the copper wire. It is concluded that copper IUDs, especially the newer devices with a more stable copper component, provide a successful fertility control method.