April 7 (Reuters) - Relypsa Inc, a U.S. maker of treatments for blood disorder hyperkalemia, is exploring a sale following a number of overtures from potential buyers, according to people familiar with the matter.

Relypsa is working with investment bank Centerview Partners Holdings LLC to review offers, the people said. The discussions are in their early stages and may not lead to a sale, the people added, asking not to be identified because the talks are private.

Interest in Relypsa has picked up in recent months after the $2.7 billion sale of ZS Pharma to AstraZeneca Plc, the people said. Relypsa and ZS Pharma are the primary competitors in a race to control the market for hyperkalemia treatment, which some estimates say could be worth more than $6 billion.

Several of the companies that unsuccessfully bid for ZS Pharma have reached out to Relypsa, the people said.

Relypsa declined to comment. Centerview did not respond to a request for comment.

(Reporting by Carl O'Donnell in New York; Editing by Chizu Nomiyama)