Barely a week after revealing he suffered from a hormone imbalance, and vowing to stay on as Apple's CEO, Steve Jobs, in a letter issued on Wednesday, told Apple employees he is stepping aside for six months.

In the letter, Jobs wrote that "during the past week I have learned that my health-related issues are more complex than I originally thought". As a result, he will take medical leave for that period. Apple Chief Operating Officer Tim Cook will stand in for Jobs in CEO duties.

It was barely 10 days ago that Jobs revealed his doctors has finally diagnosed the reason for his year-long weight loss: a hormone imbalance that was robbing the proteins needed by his body. He assured Apple employees that treatment for what he called "this nutritional problem" was "relatively simple and straightforward, and I've already begun treatment".

See all Apple news

Opinion: Why Steve Jobs is irreplaceable at Apple

He wrote then that he planned to continue in his post but promised that "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".

As COO, Cook handles Apple's global sales and operations. That includes end-to-end management of the company's supply chain, sales activities, and service and support worldwide, according to the Apple website. He also oversees the Mac division and is actively involved in developing strategic reseller and supplier deals. Before coming to Apple, he was vice president of corporate materials for Compaq.

Jobs' health has been a hot topic among pundits since last year. In July, the New York Times reported that Jobs has some health problems but that they were not life-threatening. In August the Bloomberg financial news service posted a revised obituary of Jobs by accident on its wire service.

Network World