RESEARCH TRIANGLE PARK – Leaders of two House committees have sent letters to Novo Nordisk and two other drug giants seeking information abut increasing costs of insulin, according to CNBC.

Novo Nordisk operates a huge insulin manufacturing facility in Johnston County.

CNN reports that from 2012 until 2016, the cost of insulin for people with type 1 diabetes nearly doubled, from $2,864 per year to $5,705, citing  a study out this month from the Health Care Cost Institute, a nonprofit research institute.

WRAL TechWire has reached out to the company, which is based in Denmark, for information about this report as well as a story on Tuesday in which a Senate committee led by Iowa Senator Chuck Grassley also complained about insulin prices.

Insulin pricing under review as Congress begins hearings on drug prices

Letters were sent to Novo Nordisk as well as Eli Lilly and Sanofi by Energy and Commerce Committee Chairman Frank Pallone, Jr, D-Nj, and Oversight and Investigations Subcommittee Chair Diana DeGette, D-Co, according to CNBC.

“When patients go without insulin — or ration their doses — there can be tragic consequences,” Pallone and DeGette wrote. “As one of the few manufacturers of insulin in the United States, your company is well-suited to shed light on these issues and offer potential solutions.”

So far none of the companies has commented.