A week after his first letter on the subject, Apple Inc. CEO Steve Jobs sent a memo to his staff explaining his decision to take a medical leave of absence through the end of June.

In his email, Mr. Jobs blamed both the unwanted attention over his health as well as medical problems for his decision to take a five-month sabbatical from day-to-day Apple operations. The memo was made public after the New York Stock Exchange closed yesterday at 4 p.m Eastern time.

"Unfortunately, the curiosity over my personal health continues to be a distraction not only for me and my family, but everyone else at Apple as well," Mr. Jobs said in the email. "In addition, during the past week I have learned that my health-related issues are more complex than I originally thought.

"In order to take myself out of the limelight and focus on my health, and to allow everyone at Apple to focus on delivering extraordinary products, I have decided to take a medical leave of absence until the end of June," he said.

Timothy Cook, Apple chief operating officer since 1998, will take over Mr. Jobs' day-to-day responsibilities in the interim period.

"I know he and the rest of the executive management team will do a great job," Mr. Jobs said in the letter.

"As CEO, I plan to remain involved in major strategic decisions while I am out," he said. "Our board of directors fully supports this plan.

"I look forward to seeing all of you this summer."

The Apple stock lost value in after-hours trading with this announcement. This is not surprising, since the Mr. Jobs' star factor and creative expertise are built into the company's share price and brand value.

What is happening at Apple is also common to companies that build a cult following around a leader without a clear succession plan or alternative spokesmen. The CEO's departure can rob the company of its brand value and also hit the stock.

The 53-year-old Mr. Jobs on Jan. 5 was forced to issue a letter clarifying rumors around his health.

Mr. Jobs, whose company makes the iconic Mac computers and iPhone smartphones, was forced to issue the letter a few weeks after it was announced that he would not deliver the keynote address at the Macworld Conference & Expo in San Francisco. The show for Apple enthusiasts and partners ran through Jan. 8.

This is what Mr. Jobs said in the first letter sent Jan. 5:

Dear Apple Community,
For the first time in a decade, I'm getting to spend the holiday season with my family, rather than intensely preparing for a Macworld keynote.

Unfortunately, my decision to have Phil [Schiller] deliver the Macworld keynote set off another flurry of rumors about my health, with some even publishing stories of me on my deathbed.

I've decided to share something very personal with the Apple community so that we can all relax and enjoy the show tomorrow.

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.

The remedy for this nutritional problem is relatively simple and straightforward, and I've already begun treatment. But, just like I didn't lose this much weight and body mass in a week or a month, my doctors expect it will take me until late this Spring to regain it. I will continue as Apple's CEO during my 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. I hope the Apple community will support me in my recovery and know that I will always put what is best for Apple first.

So now I've said more than I wanted to say, and all that I am going to say, about this.

Steve