Apple CEO Steve Jobs--long the subject of health rumors--released an open letter to Apple's community Monday morning, explaning Jobs recent decision to not keynote the upcoming MacWorld conference. According to the letter, Jobs is suffering from a "hormone imbalance" which has been causing jobs to lose weight this year. Jobs said that the reason for the weight loss has been a "mystery to me and my doctors" until recently. Jobs said that he would continue as Apple's CEO while he recovers from the health problem. Jobs was diagnosed with pancreatic cancer five years ago; the announcement that Jobs would not keynote MacWorld set off a flurry of rumors in recent weeks about Jobs health and the possibility of his pancreatic cancer taking a turn for the worse.