By AppleInsider Staff

Published: 09:00 AM EST

In an open letter to Apple fans Monday, Steve Jobs revealed that he's being treated for a hormone imbalance that has contributed to his rapid weight loss, but says he plans to remain Apple's CEO for the foreseeable future.

The decision to have marketing chief Phil Schiller deliver tomorrow's Macworld keynote "set off another flurry of rumors about my health, with some even publishing stories of me on my deathbed," Jobs wrote, explaining that for the first time in over a decade he's spending the holiday season with his family, rather than intensely preparing for a presentation.

"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," he continued.

"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 said he's begun treatment for the nutritional problem. And while the solution is relatively simple and straightforward, he warned that it will take until late Spring for him to regain much of the weight he lost during the 2008 calendar year.

"I will continue as Apple’s CEO during my recovery," he wrote. "I have given more than my all to Apple for the past 11 years now. I will be the first one to step up and tell our Board of Directors if I can no longer continue to fulfill my duties as Apple’s CEO. I hope the Apple community will support me in my recovery and know that I will always put what is best for Apple first."

In a separate statement issued Monday, Apple's Board of Directors said "Apple is very lucky to have Steve as its leader and CEO, and he deserves our complete and unwavering support during his recuperation."

"It is widely recognized both inside and outside of Apple that Steve Jobs is one of the most talented and effective CEOs in the world," the statement said. "As we have said before, if there ever comes a day when Steve wants to retire or for other reasons cannot continue to fulfill his duties as Apple’s CEO, you will know it."

Jobs said he decided to share details of his personal situation with the Apple community so that everyone "can all relax and enjoy the show tomorrow."