So, here we go:
Ever since I was about 12 I've had irrational, violent mood swings. My family noticed this and told me nothing, despite my family history of diabetes and thyroid problems (which also entails hypoglycaemea - hence the moodswings). By the time I was 15 I'd come to terms with the mood swings on my own, believing them to be part of my altogether crappy personality related to adolescent hormones and the like, and felt better and calmer for it. I'm now 18 and my family have just told me that they knew all along, whereas I only found out the official explanation a few days ago.
Unfortunately, I can receive no treatment for my thyroid issues because of a liver disorder I have which means that any blood tests I have will give inconclusive and pretty much random results, so any treatment would have to be based solely on the superficial symptoms (which are not all apparent at the moment, so I'm told).
I can't eat bizarre amounts of chocolate, since this would send me into diabetes-land, and I can drink myself stupid as my liver is also quite likely to be weakened by the disorder and I'm in a high-risk category for cyrrosis. (No one can be sure of this, of course, because the blood tests have no conclusive results, so it's all based on immediate family history and the likelihood of genetic disorders... whoopee)
I love my body, it's just so wacky.