Three cases of profound hypothyroidism, 2 of whom lapsed into myxoedema coma are reported. All 3 cases presented over a 5 week period. Modern management, especially the use of intensive care, has improved the outcome. All 3 cases survived. Treated hypothyroid patients frequently discontinue their medicines and constitute the majority of patients presenting in myxoedema coma. It is vital that the patient and their families are made aware that treatment must be life-long. Hypothalamic-pituitary dynamic studies with thyrotrophin-releasing hormone (TRH) and luteinizing hormone-releasing hormone (LHRH) were also performed and are reported.