Background Subclinical apoplexy of pituitary functional adenoma can cause spontaneous remission of hormone hypersecretion.The typical presence of pituitary growth hormone (GH) adenoma is gigantism and/or acromegaly.We investigated the clinical characteristics of patients with spontaneous partial remission of acromegaly or gigantism due to subclinical apoplexy of GH adenoma.Methods Six patients with spontaneous remission of acromegaly or gigantism were enrolled.The clinical characteristics,endocrinological evaluation and imageological characteristics were retrospectively analyzed.Results In these cases,the initial clinical presences were diabetes mellitus or hypogonadism.No abrupt headache,vomiting,visual function impairment,or conscious disturbance had ever been complained of.The base levels of GH and insulin growth factor-1 (IGF-1) were normal or higher,but nadir GH levels were all still ＞1 μg/L in 75 g oral glucose tolerance test.Magnetic resonance imaging detected enlarged sella,partial empty sella and compressed pituitary.The transsphenoidal surgery was performed in 2 cases,and the other patients were conservatively managed.All the patients were in clinical remission.Conclusions When the clinical presences,endocrine evaluation,biochemical examination and imageology indicate spontaneous remission of GH hypersecretion in patients with gigantism or acromegaly,the diagnosis of subclinical apoplexy of pituitary GH adenoma should be presumed.To these patients,conservative therapy may be appropriate.