Dozens of women urged the U.S. Food and Drug Administration on Thursday to withdraw Bayer AG's permanent contraceptive device, Essure, saying not enough is known about its potential to harm users.

The FDA called a meeting of its advisory panel to weigh the benefits and risks of Essure following complaints from thousands of women who said it had caused life-altering side effects from chronic pain and bleeding to autoimmune disorders such as psoriasis and lupus.

Essure consists of two small nickel-titanium coils which are inserted through the vagina into the fallopian tubes. The device was billed as a non-surgical alternative to tubal ligation and was welcomed by doctors when it was first cleared by the FDA in 2002.

Since then, a growing number of women have reported problems. Thousands joined a Facebook group called "Essure Problems" where women share their experiences with the device.

The group pressed the FDA to investigate the device, which initially appeared at least as safe and effective as tubal ligation, the other method by which women can become sterilized.

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More than 5,000 adverse events have been reported to the FDA, though it is not always clear what role Essure played in the event.

Mark Bell, a metals engineering consultant who was one of more than 40 speakers at the meeting, said he analyzed a number of Essure devices after they had been removed from patients, and believes there are latent manufacturing processing problems with the devices.

"It's my expert option is that Essure is not a safe product," he said.

Some women discussed how their coils migrated from the fallopian tube into the pelvic cavity or around the bowel causing acute pelvic pain. Others described debilitating fatigue and the onset of symptoms suggestive of a systemic immune system response to the device.

The FDA asked the panel to discuss whether the device should be restricted in some patient groups, or whether changes should be made to the product's label. It also asked the panel to recommend whether additional clinical trials should be conducted.

The committee was not asked to formally vote on their recommendations but the FDA will weigh their opinions as it decides what to do about the device.

Panelists discussed the role of nickel or other metals in potentially sparking symptoms.

"It would be worth collecting information about nickel sensitivity to see if it is connected with some of the symptoms," said Marsha Wills-Karp, chair of the department of environmental health sciences at Johns Hopkins University.

The standard skin patch test for nickel allergy does not reliably predict whether a person will have a systemic allergic reaction and there is no FDA-approved blood test to measure a person's hypersensitivity before being implanted with the device.

Panelists recommended strengthening the product label to provide more information about potential adverse events and the creation of a patient registry to track adverse events.

They also recommended more training for doctors, including how to remove the coils and suggested a protocol be developed to intervene earlier when patients complain about persistent pain.