I am 31, female, have had 4 kids, have had hypothyroidism for 12 years now, in the last 2 years I have had trouble with my thyroid. I was on 200mcg of thyroxine in January 11 and had a blood test saying it was over active, had a test 6 weeks later after dropping to 150mcg and they said it was perfect. Had a routine thyroid test last week after losing 30kg (had lap band surgery 6 weeks ago) and came back even more overactive than back in January before I had even started to lose weight. Have you got any idea what might be causing this?