MELBOURNE, Aug 28 (Reuters) - Australia's Fortescue said on Monday its metals division head and co-CEO Fiona Hick was leaving after less than six months in the role, being replaced by Dino Otranto.

The world's forth-largest iron ore miner, which is overseen by executive chairman, founder, and major shareholder Andrew Forrest, has been beset by senior management turnover over the past two years.

Hick, who took on the co-CEO role in February, will depart the company by mutual decision, with Otranto, who was appointed head of the company's iron ore division two years ago, stepping into the role.

"It's been a bit of a revolving door, and quick, quicker than you'd expect," said Barrenjoey analyst Glyn Lawcock.

"But their operating performance has been second to none. Dino hasn't missed a beat. Volume has continued to grow and they have still done a good job and keeping their costs down."

Fortescue on Monday reported a 23% drop in annual profit, hurt by declining prices for iron ore and the brunt of an impairment charge of $726 million.

Mark Hutchinson will continue to lead Fortescue Energy and both leaders will report to Forrest and the Fortescue Board, the company said.

Ian Wells, Fortescue's chief financial officer, stepped down at the end of January, meaning almost all of the senior executive leadership team from a year previous had changed. (Reporting by Melanie Burton in Melbourne and Aishwarya Nair in Bengaluru; Editing by Kim Coghill and Lincoln Feast)