Hypothyroidism can cause a cholesterol problem (as well as fatigue, headaches, mood
swings, itchy skin, confused thoughts,
depression, and many other fun
symptoms). My surgeon actually suggested that my untreated hypothyroidism may have caused such a problem with my cholesterol that it lead to my gallstones. (First attack at 22.)
I have heard others say part of it is also genetic- if a parent had problems with a gallbladder then their kid might too.