Apple Inc. co-founder and Chief Executive Steve Jobs said Wednesday he is taking a medical leave until the end of June - just a week after the cancer survivor tried to assure investors and employees his recent weight loss was caused by an easily treatable hormone deficiency.

Apple (nasdaq: AAPL - news - people )'s stock plunged 7 percent.

Jobs, 53, said in a letter last week that he would remain at Apple's helm despite the hormone problem, and that he had already begun a "relatively simple and straightforward" treatment. But in an e-mail to employees Wednesday, Jobs backtracked.

"During the past week I have learned that my health-related issues are more complex than I originally thought," he wrote.

Apple's shares have surged and crashed over the last year in step with rumors or news about the CEO's health and his gaunt appearance. While the top executive's health is an issue for investors in any company, at Apple the level of concern reaches fever pitch because Jobs has a hand in everything from ideas for new products to the way they're marketed. Investors fear that without Jobs, Apple will not be able to sustain its growth of the last decade, which has seen Apple branch out from its Mac computers into the iPod and the iPhone.

Last week, Jobs said his disclosure of his hormone problem was "more than I wanted to say, and all that I am going to say" about his health. It came on the eve of Macworld, the biggest Apple trade show of the year, and Jobs said he wanted everyone to relax and enjoy the show.

Even so, the limited amount of medical information in that announcement did little to soothe Wall Street's nerves, and in interviews last week analysts predicted that the health watch would continue.