Just a week after trying to assure investors of his health, Apple chief Steve Jobs announced Wednesday he will take a leave of absence till end-June because of health problems more complex than thought, causing shares to plunge and analysts speculating over the leadership of the tech company.

Jobs, 53, said last week that his dramatic weight loss was from hormone imbalance. In a vague statement released Wednesday, Jobs did not specify the cause of his poor health.

The next six months are going to be basically a trial period for Tim Cook to be CEO, said Brian Marshall at Broadpoint Amtech.

If that period goes well, my expectation is that Steve will pass the baton over to Tim in June and basically Steve will be his senior adviser.

Apple is more dependent on its CEO than most other companies which leave analysts and investors concerned over who will lead the company while Jobs takes his leave of absence.

Steve is a critical judge of the company's business, and that maestro role that he performs is what makes Apple great. But there is no maestro-in-training to take over Steve's role, said Roger Kay of Endpoint Technologies.