Apple Inc. founder and chief executive Steve Jobs said he will take a medical leave of absence from the company until the end of June, according to an e-mail from the CEO to Apple employees.
"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," Jobs wrote in the e-mail. "In addition, during the past week I have learned that my health-related issues are more complex than I originally thought."
Tim Cook, Apple's chief operating officer, will take on the chief executive responsibilities until Jobs' return.
Apple's shares fell 6.54 percent in after-hours trading on the news of Jobs' medical leave.
"Steve Jobs is a pop culture icon," said, Avi Greengart, an industry analyst with research firm Current Analysis. "There's definitely the notion that Steve Jobs is Apple."
"Where Steve Jobs' [absence] will be most acutely felt long-term is deciding what products to kill, what products to keep … making the decisions that enable a healthy set of platforms," he said, adding that Jobs's e-mail indicates that he will continue to be involved in decision-making while he is on leave.
"Apple has a very deep bench - there are a lot of talented individuals up and down," Greengart told ABCNews.com. But he also said that no matter how talented Jobs' successor may be, he or she may not have the same pull in terms of decision-making.
"He is the leader. He is their icon," said Piper Jaffray analyst Gene Munster. "Without him, there will be some questions about where this goes in the future."
The shift comes a little more than a week after Jobs issued a statement downplaying widespread speculation about his apparent weight loss over the past year, including rumors that a pancreatic condition he had suffered had worsened. The 53-year-old attributed his gaunt appearance to an easily treated hormone imbalance.
Jobs' assertion is buoyed by the fact that the pancreatic condition he survived -- called a neuroendocrine tumor, or NET -- is much less deadly than the more common form of pancreatic cancer that took the lives of "Last Lecture" professor Randy Pausch and New York Times reporter Dith Pran, and which actor Patrick Swayze now faces.
Only about 2,000 to 3,000 neuroendocrine tumor cases are diagnosed in the United States each year, and up to half of those with malignant forms of these tumors are still alive after five years, according to statistics from the National Cancer Institute. When those with nonmalignant forms of these tumors are included, the survival rate is even higher.
Conversely, doctors estimate that about 30,000 people were diagnosed with the deadlier form of pancreatic cancer this year, which has a five-year survival rate of about 5 percent.
"My decision to have [Apple marketing chief] 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," Jobs noted in a statement issued Jan. 5, on the first day of the MacWorld 2009 conference. "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."
Jobs further noted in his Jan. 5 letter that the remedy for the problem is "relatively simple and straightforward," and that he has already begun treatment to correct the condition.
An e-mailed message to an Apple spokesperson for further comment was not immediately returned. Following Jobs' announcement, Apple Inc. released a statement indicating that Jobs will continue to hold the CEO post for the company.
Pancreatic cancer experts said an effective lockdown on Jobs' medical particulars since he first announced he had a pancreatic tumor in 2004 makes it difficult to determine for certain the exact nature of his condition.
"He's done a very good job of keeping this private," said Dr. Harold Frucht, associate professor of clinical medicine at Columbia University.
But he said that judging from the information available, it is unlikely that Jobs required a Whipple procedure -- an operation that removes a large portion of the pancreas and can lead to profound hormonal imbalances.
Instead, he said, he believes the surgeon who operated on Jobs probably performed what is called an enucleation -- a procedure in which a doctor in essence scoops a tumor out of the organ, leaving most of the pancreas intact.
"A lot of surgeons would have done a Whipple procedure, but for neuroendocrine tumors this is not generally necessary," Frucht said. "Good surgeons who have dealt with a lot of these tumors would conduct the surgery without taking out the pancreas."
Frucht said hormonal imbalances are not rare in patients with a neuroendocrine tumor, and these symptoms can resurface years after these tumors are removed. And he concurred that if indeed Jobs had suffered from a neuroendocrine tumor, the treatment for rebalancing his hormone levels would likely be a simple matter.
"Probably up to 60 percent of patients with a biochemical cure after surgery -- all hormone levels are normal and no tumor on imaging -- will have a recurrence of hormone excess production," he said. "Treatment would be simple -- medical treatment to treat the manifestations of excess hormone production."
However, Dr. Anne Peters, director of USC clinical diabetes programs, said it is still possible that Jobs underwent a Whipple procedure, the operation most often performed for the most common form of pancreatic cancer. And she said the downstream effects of this procedure can also lead to weight loss, as the operation normally removes the tissue responsible for producing important digestive enzymes.
"Life after a Whipple is difficult, because these hormones and enzymes need to be replaced, and often the treatments aren't quite as good as the body's own production of them," she said. "My post-Whipple patients tend to be thin, and have to work hard to maintain adequate nutrition."
She added that the treatment for this type of lingering condition are also straightforward, though they must be maintained for life.