Steve Jobs reveals his mystery illness

After a year of concerns about his gaunt appearance, months of rumours about his declining health and a flurry of speculation a week ago that he may even be at death's door, Apple founder Steve Jobs has broken his silence to insist he remains firmly at the helm of the consumer gadgets giant.

He is suffering a "hormone imbalance", he said in a letter to the Apple faithful gathering at the annual Macworld conference in San Francisco yesterday. That is causing him to lose weight, he said, but he has already begun treatment.

The statement was designed to stem a growing panic over Apple's future, with everyone from shareholders to faithful customers fearful that the company would lose its edge without the leadership of Mr Jobs. He returned from exile a decade ago and restored Apple's fortunes with the launch of the iPod, a new range of must-have Macintosh laptops, and finally the iPhone.

"I've decided to share something very personal with the Apple community so that we can all relax and enjoy the show," he told Macworld attendees. "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 number one 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. The remedy for this nutritional problem is relatively simple and straightforward."

The statement comes after a long line of seemingly contradictory statements from Apple's public relations team, and two weeks after the company said Mr Jobs would not be giving the keynote address at the Macworld conference – an annual institution, where the turtle-necked guru usually strides on to stage to announce the latest world-changing Apple device.

Mr Jobs' medical history includes a struggle with a rare, treatable pancreatic cancer in 2004, and there were rumours last summer that the cancer had returned. Between Christmas and New Year, a tech industry blog created a sensation by claiming Mr Jobs' health was "rapidly declining" and that having Apple's marketing chief Philip Schiller present the keynote address at Macworld was part of a plan to ready the world for a post-Jobs Apple – a story the company immediately denied.

Hormonal imbalance: Symptoms and treatment

*Hormonal imbalance is a known side-effect of pancreatic cancer. One of its symptoms is weight loss. Mr Jobs has not said that the condition he is suffering is linked with his earlier brush with cancer. But yesterday's admission is certain to spark speculation. Pancreatic cancer originates in the pancreas, which produces hormones such as insulin. Mr Jobs had a rare cancer type that originates in the pancreatic cells that produce hormones. A cancerous growth in the organ could lead to the imbalance. Mr Jobs says the remedy for his "nutritional" problem is simple and he has begun treatment which should see him regain weight by the spring. Jeremy Laurance, Health Editor