Hepatic haemangioendothelioma is a rare vascular tumour in infants and may be associated with a unique form of thyroid function abnormalities. Hepatic haemangioendotheliomata is capable of producing an excess of the thyroid hormone inactivating enzyme, type 3 iodothyronine deiodinase. The increased enzyme activity leads to rapid degradation of thyroid hormones, resulting in frank hypothyroidism. We report a case of a three-month-old neonate with multiple hepatic haemangioendotheliomata and associated hypothyroidism. The patient required increasing doses of thyroid hormone.