A 16-year-old girl had symptoms of vomiting, malaise and weight loss for two months. Blood tests revealed an elevated activity of liver enzymes and hyperthyroidism. Although the patient at first denied the possibility of pregnancy, a pregnancy was subsequently confirmed. Hyperemesis gravidarum was diagnosed based on the combination of the clinical symptoms, pregnancy and increased serum human chorionic gonadotrophin and oestradiol. Hyperemesis gravidarum also explained the demonstrated biochemical hyperthyroidism and elevated liver enzyme levels. Rapid alleviation of all the clinical symptoms was seen after termination of this unwanted pregnancy. Although vomiting, malaise and weight loss in children can have many different causes, in girls at a sexually mature age a pregnancy with possible hyperemesis gravidarum should certainly also be considered and a gynaecological examination performed.