A 33-year-old man was referred to the Department of Respiratory Medicine in our hospital due to severe hypercapnic respiratory failure in March 2008. His respiratory function test showed severe restrictive pulmonary dysfunction, and respiratory muscle strength assessed by measuring maximal static expiratory and inspiratory mouth pressures was severely impaired. After non-invasive positive pressure ventilation was started, he was referred to the Endocrinology Department as he was diagnosed as hypopituitarism in his childhood. Pituitary MRI demonstrated pituitary stalk agenesis, and hormonal examination showed that he had severe growth hormone (GH) deficiency. GH replacement therapy was started in August 2008 and his arterial blood gas values and respiratory muscle strength were improved in 6 months. The current case demonstrated that GH deficiency could be a cause of severe respiratory failure.