SAN FRANCISCO - APPLE'S iconic chief executive Steve Jobs, dogged by speculation about his health, announced on Monday that he is being treated for a 'hormone imbalance' but will remain head of the company.

'I've decided to share something very personal with the Apple community so that we can all relax and enjoy the show tomorrow,' said Mr Jobs, co-founder of the California company behind the Macintosh computer, iPhone and iPod.

'As many of you know, I have been losing weight throughout 2008,' said Mr Jobs, who underwent surgery for pancreatic cancer in 2004 and looked extremely gaunt at his last public appearance in September.

'The reason has been a mystery to me and my doctors,' the Apple CEO said.

'A few weeks ago, I decided that getting to the root cause of this and reversing it needed to become my number one priority.

'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,' Mr Jobs said.

'Sophisticated blood tests have confirmed this diagnosis,' he said. 'The remedy for this nutritional problem is relatively simple and straightforward, and I've already begun treatment.

'But, just like I didn't lose this much weight and body mass in a week or a month, my doctors expect it will take me until late this Spring to regain it,' Mr Jobs said, adding: 'I will continue as Apple's CEO during my recovery.'

The Apple chief said he '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.

'I hope the Apple community will support me in my recovery and know that I will always put what is best for Apple first,' he said. 'So now I've said more than I wanted to say, and all that I am going to say, about this.'

In a statement released simultaneously with Mr Jobs's letter, the Apple board described him as 'one of the most talented and effective CEOs in the world' and said 'if there ever comes a day when Steve wants to retire or for other reasons cannot continue to fulfill his duties as Apple's CEO, you will know it.'

'Apple is very lucky to have Steve as its leader and CEO, and he deserves our complete and unwavering support during his recuperation. He most certainly has that from Apple and its board.'

Apple's share price rallied in reaction to the announcement, gaining 4.22 per cent in New York to close at US$94.58 dollars.

Apple has been notoriously secretive about Mr Jobs's health and was criticised by some analysts for failing to acknowledge his medical issues sooner.

'It's an announcement that could have been made last month and, given the way that Jobs and Apple have traded on his reputation to pitch the company, it should have been,' wrote Staci Kramer on paidContent.org.

Hormonal imbalance is a common symptom of pancreatic cancer and could signal that Mr Jobs isn't done battling the often terminal illness, said Rob Enderle of the Enderle Group in Silicon Valley.

'Steve Jobs is not immortal or super human,' Mr Enderle said, adding that the board of Apple is shirking its duty if it isn't grooming a successor. 'The people Apple has on the bench cannot take the place of Steve Jobs,' he said.

NPD analyst Stephen Baker disagreed, saying that while Mr Jobs is the driving force at Apple, they have 'plenty of talented people to take over' the helm.

Mark Margevicius of research firm Gartner said Mr Jobs has 'great people working for him' but 'Apple very much needs him to drive, innovate and lead.'

'The thing that differentiates Apple is him, he's a man of great vision.'

Speculation about Mr Jobs's health had been rampant since it was announced last month that for the first time in 11 years he would not give the keynote speech at Macworld, the annual cult-like gathering of Apple devotees.

Marketing vice president Phil Schiller is to give the keynote at Macworld, which runs from Jan 6-9 and features more than 450 companies promoting gadgets, gear, software or services tailored for Apple products.

Born in San Francisco on Feb 24, 1955 to a single mother and adopted at a young age, Mr Jobs founded Apple in 1976 with engineer Steve Wozniak after dropping out of college.

He left the company in 1985 after an internal power struggle but returned in 1996 and is credited with reversing Apple's fortunes by launching the iPod and the iPhone.

Under Mr Jobs, Apple has also made its Macintosh computers more compatible with Windows-based PC programs and boosted its share of a market long ruled by machines based on Microsoft software. -- AFP