Apple's CEO Steve Jobs has revealed that he is being treated for a “hormone imbalance” and has been told to rest by doctors.
Jobs sparked fresh health fears last month after it was announced that he would no longer give the keynote speech at Apple's Macworld conference.
In a letter sent to the Apple Community, Jobs said he had decided to “share something very personal” in order to quash speculation that he was on his “death bed”.
He wrote: “As many of you know, I have been losing weight throughout 2008. The reason has been a mystery to me and my doctors. A few weeks ago, I decided that getting to the root cause of this and reversing it needed to become my #1 priority.
“Fortunately, after further testing, my doctors think they have found the cause -- a hormone imbalance that has been "robbing" me of the proteins my body needs to be healthy. Sophisticated blood tests have confirmed this diagnosis.”
Jobs, who survived pancreatic cancer in 2004, said he would continue to act as Apple's chief executive while he received treatment.
A statement from Apple's Board said Jobs would have their “complete and unwavering support during his recuperation”.
Jobs' letter has arrived a day before he would have been due to deliver the Macworld keynote address in San Francisco.
Apple’s senior vice president of worldwide product marketing, Phil Shiller, is due to deliver the speech in Jobs' place.