Steve Jobs’ health has been much discussed, and of concern particularly to nervous Apple shareholders.

He recently took a 5-month leave of absence because his condition was “more complex” than originally thought.

Since that announcement, medical pundits have not been in short supply trying to explain what’s going on. Of the speculation that I’ve read thus far, here are two leading possibilities.

1) Cancer recurrence. It is known that Mr. Jobs underwent surgery for a neuroendocrine pancreatic tumor in 2004. Most cases are removed without complication, but approximately half recur. If this is the case, it is possible that a new mass may be leading his pancreas to over-produce hormones, such as insulin, that can lead to rapid weight loss. I believe this is the most likely explanation.

If there is indeed cancer recurrence, these types of tumors often spread to the liver. There is some speculation that if this is the case, a liver transplant is a possibility.

2) Side effects. The procedure that Mr. Jobs likely underwent in 2004, known as the Whipple procedure, is a major operation, leaving approximately 30 to 50 percent of the pancreas. A partial pancreas may hinder digestion, leading to weight loss being a side effect of the procedure. However, it is unlikely that these side effects would lead to an extended medical leave.

In any case, this is more than a simple “hormone imbalance.” I wish Mr. Jobs all the best with this recent setback in his health.