Hypothyroidism is occasionally developed during human growth hormone (hGH) treatment. However, there is little evidence for the development of hyperthyroidism associated with hGH treatment. The development of hyperthyroidism associated with hGH treatment has rarely been reported. Recently we experienced one case. Herein we describe the clinical course and outcome of hyperthyroidism in this patient. This case is familial short stature. This patient developed hyperthyroidism during 18 months treatment with hGH. He showed positive thyrotropin-binding inhibiting immunoglobulin (TBII). He did not show typical clinical symptoms of hyperthyroidism. After treatment with methimazole for 2months, thyroid function returned to normal. Hyperthyroidism associated with hGH treatment may occur by chance. However, incidence of hyperthyroidism among patients with familial short stature and the absence of a family history of it indicate that hGH may have causative effect in the development of hyperthyroidism.