There may be many causes
for the high triglycerides, such as obesity, high sugar diets,
diabetes mellitus, excess alcohol intake, familial disposition. However, the most important is Unknown causes which are known as idiopathic factors, such factors which have not been explained as yet.
I am sure that you would be practicing measures to ensure that they remain in the safe range from you. You may find more information at: http://en.wikipedia.