With rumors swirling about the health of Steve Jobs after Apple's CEO decided not to deliver the keynote address at the Macworld Conference & Expo show this week, Jobs revealed the truth behind his absence.

In a letter, Jobs said he's "decided to share something very personal with the Apple community so that we can all relax and enjoy the show." Jobs went on to write that he's been mysteriously losing weight throughout the year and that a few weeks ago he decided to make it his "No. 1 priority" to figure out why.

After undergoing a series of tests, Jobs said his doctors believe a hormone imbalance has been "robbing" him of proteins that his body needs to be healthy. Jobs wrote that he has already begun a "relatively simple and straightforward" treatment, but that he will not be able to regain all of the lost weight until late spring.

Jobs said he will remain the CEO at Apple during his recovery.

"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," Jobs wrote in a letter. "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, 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. He most certainly has that from Apple and its Board."