Steve Jobs has suffered dramatic weight loss in the past year

Apple Chief Executive Steve Jobs is to take medical leave until the end of June, saying his health issues were more complex than he first thought.

Mr Jobs revealed last week he was being treated for a "hormone imbalance" but was staying on as the firm's head.

Chief Operating Officer Tim Cook will stand in while Mr Jobs is away.

Diagnosed with pancreatic cancer in 2004, Mr Jobs had appeared increasingly gaunt at recent public appearances, sparking rumours about his health.

Speculation about his health had intensified since December, after Apple said Mr Jobs would not be making his annual keynote address at the Macworld conference in San Francisco.

Directors' support

In an email to employees on Wednesday, Mr Jobs said: "In order to take myself out of the limelight and focus on my health... I have decided to take a medical leave of absence until the end of June.

"As CEO, I plan to remain involved in major strategic decisions while I am out. Our board of directors fully supports this plan."

In last week's statement, Mr Jobs said doctors thought they had found the cause for his weight loss: "a hormone imbalance that has been robbing me of the proteins my body needs to be healthy".

Apple's board said it was giving him "complete and unwavering support".

Apple's share price fell following the announcement, showing how closely the company's fortunes are still identified with the person who helped create it, says the BBC's Greg Wood in New York.

Mr Jobs co-founded Apple in 1976, but left in 1985 to start another computer venture. He returned to Apple in 1997 and became full-time chief executive once again in 2000.