NEW YORK (TheStreet) -- Shares of Sientra (SIEN) - Get Report were falling 42.95% to $11.74 on heavy trading volume Thursday after the breast implant and breast tissue expander maker said the U.K.'s Medicines and Healthcare Products Regulatory Agency suspended CE certification of all of its medical devices made by Silimed.

In a letter filed with the SEC and sent to Sientra's plastic surgeon clients, CEO Hani Zeini said that the "MHRA announcement has no applicability to Sientra's products as it is applicable only to the distribution of Silimed's CE-marked implants in Europe."

Zeini also pointed out that Sientra's products are FDA-regulated and PMA-approved. "Sientra's breast implants and our other products continue to be marketed and available in the United States and there has been no change to the regulatory status of Sientra's FDA-approved breast implants," the CEO wrote.

The company recently said that it relies on Silimed, a third-party manufacturer based in Brazil, as its sole source to manufacture and supply its silicone gel breast implants, tissue expanders, and other products.

About 4.8 million shares of Sientra were traded by 2:27 p.m. Thursday, well above the company's average trading volume of about 70,000 shares a day.

SIEN data by YCharts

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