APPLE HAS moved to quell speculation about the health of its chief executive Steve Jobs by announcing he has a hormone imbalance which caused him to lose weight throughout 2008.

Mr Jobs traditionally gives the keynote address at Macworld, the annual conference for Apple users, which is being held in San Francisco this week.

Last month, Apple announced its chief executive would not be appearing at the show and that this would be the last time Apple participated at Macworld, which is organised by a separate company

The news that the keynote address would be presented by Philip Schiller, the technology firm’s senior vice-president of marketing, led to speculation that the company’s co-founder was terminally ill, a fact which Mr Jobs acknowledged in an open letter to the “Apple community” which the company published yesterday.

Mr Jobs had treatment for pancreatic cancer in 2004 but both he and the company have been tight-lipped about his health since then, claiming it was a personal matter.

During the few public appearances the Apple co-founder made in 2008, he looked extremely gaunt. In his letter, he acknowledged that he had been losing weight last year for reasons unknown to both he and his doctors. “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,” he wrote yesterday.

He said the treatment, which he has begun, is relatively simple and straightforward, but it is likely to be late spring before he regains weight. Mr Jobs said he will continue as chief executive during that time. “I will be the first one to step up and tell our board of directors if I can no longer continue to fulfil my duties as Apple’s CEO.”

Apple’s board of directors, which includes former US vice-president Al Gore and Google chief executive Eric Schmidt, issued a statement saying Mr Jobs has their “complete and unwavering support during his recuperation”.

Although the note was out of character for both Mr Jobs and Apple, his parting line suggests that he wants to draw a line under speculation about his health.

“So now I’ve said more than I wanted to say, and all that I am going to say, about this,” he finished the letter.