Powerful committees in the U.S. Congress held hearings on Tuesday on insulin affordability and high prescription drug prices, an issue both chambers have said is a top priority for the year.

The House Oversight Committee, chaired by Democratic Representative Elijah Cummings, and the Senate Finance Committee, chaired by Republican Senator Chuck Grassley, brought in patient advocates and health policy experts to discuss the burden of high drug costs on consumers and sky-rocketing prices.

Both committees also focused on insulin, which those with type 1 diabetes and some with type 2 diabetes depend on.

High prescription drug costs have consistently polled as a top voter concern and have been a top priority of the administration of U.S. President Donald Trump.

It remains unclear whether Democrats, who control the U.S. House of Representatives, and Republicans, who control the U.S. Senate, will find a bipartisan way to address rising drug costs.

The annual cost of insulin for treating a type 1 diabetes patient in the United States nearly doubled from 2012 to 2016 to $5,705 from $2,864, according to a recent study.

Cummings earlier this month sent letters to 12 pharmaceutical companies asking for detailed information on their pricing practices. He focused on medicines whose costs rose the most over the last five years, including several diabetes medications.

Democrats in the Senate and House earlier this month, including Cummings, also introduced a series of bills aimed at bringing down drug costs. No Republicans have signed onto the legislation.

Ron Wyden, the ranking member of the Senate Finance Committee, said in a statement that the committee invited the heads of several large drug companies to testify on Tuesday, but none were willing to come.