NEW YORK (Reuters) - Annaly Capital Management Inc (>> Annaly Capital Management, Inc.) co-founder and co-chief executive Michael Farrell, who underwent cancer treatment earlier this year, has passed away, the New York-listed mortgage real estate investment trust said in a statement on Sunday.

The cause of Farrell's death was not disclosed in the statement. On October 10, the firm said it had appointed Annaly co-founder Wellington Denahan-Norris, 48, as co-CEO to allow Farrell, 61, to focus on his cancer treatment.

"He was a fantastic leader and friend and will be greatly missed. Our hearts go out to his family and all those who were fortunate enough to know him," Annaly said in the statement on Sunday.

Before co-founding Annaly in 1996, Farrell was managing director in the fixed income department of Wertheim Schroder & Co Inc. He started his career in 1971 at E.F. Hutton and Co, a stock brokerage, and went on to work at Merrill Lynch, Morgan Stanley (>> Morgan Stanley) and L.F. Rothschild Mortgage Capital Inc.

Annaly announced in January that Farrell was undergoing chemotherapy and said in May that his cancer was in remission and that his treatment was complete. But he had to undergo additional treatment since August.

Annaly manages a portfolio mostly U.S. government agency mortgage-backed securities. Since its initial public offering in 1997, Annaly says it has paid out over $8 billion in dividends to its shareholders.

(Reporting by Greg Roumeliotis in New York; Editing by Marguerita Choy)

Stocks treated in this article : Morgan Stanley, Annaly Capital Management, Inc.