Steve Jobs reassures investors about health

Reveals hormone imbalance as cause of weight loss

NEW YORK -- Steve Jobs has been suffering from a hormone imbalance, but is healthy enough to continue to fulfill his job functions, the Apple CEO said in an open letter Monday -- a day ahead of the annual Macworld Conference & Expo event.

Jobs, who also serves on the board of Walt Disney, traditionally gives the keynote speech there, but recently announced that Phil Schiller, Apple's senior vp worldwide product marketing, will do so this year. That set off a flurry of renewed speculation about Jobs' health after the tech pioneer lost weight last year.

Apple shares rose in early Monday trading.

"As many of you know, I have been losing weight throughout 2008," Jobs said in a letter addressing the Apple community. "The reason has been a mystery to me and my doctors."

After recently making this issue and further tests his top priority, Jobs said "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."

Jobs, criticized by some investors as not forthcoming enough on his health, didn't detail possible causes for the hormone imbalance. But he called it a "nutritional problem" with a "relatively simple and straightforward" treatment that he has begun.

"My doctors expect it will take me until late this spring to regain (my weight,)" he said before promising: "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."

Apple hasn't outlined any potential succession plans so far in case Jobs leaves the CEO post.

"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 board said in a statement on Monday.

"Apple is very lucky to have Steve as its leader and CEO, and he deserves our complete and unwavering support during his recuperation. He most certainly has that from Apple and its board."