What Causes Elevated Trigliceride Levels?

I am a 50 year old man that works out every day for at least two hrs I am 5 10 and weigh 192lbs. I am in great shape, I only drink a couple of beers a week and eat mainly chicken and salads. I recently had an insurance exam when they told me my trigliceride levels were over 1200.. my ? is how can this be possible, I don t fit the criteria for this elevated #, and what can I do to bring it down? thx karl