How do high levels of alt affect offsprings?

Not really: Alt is a reflection of liver enzyme activity. Per se, it does not mean you have an inherited disease. Elevation can be related to things like taking tylenol, (acetaminophen) or drinking too much, having a tumor, etc. There are hundreds of things that can cause alt elevation -- but it is usually not a genetic problem.

How high?: There is wide range for ALT levels in different diseases. Mild elevation in some one who take alcohol, would be expected and would not affect the offspring.