Background Little information about the current management of patients with thyroid-stimulating hormone (TSH)-secreting pituitary adenomas or about the usefulness of the somatostatin analogue octreotide was contained in the literature.This study aimed to report the efficacy and safety of the long-acting octreotide formulation in patients with TSH-secreting pituitary adenomas after incomplete surgery and octreotide treatment failure.Methods Fifteen patients with TSH-secreting pituitary adenomas (8 men and 7 women),who previously underwent incomplete surgical resection and/or adjuvant radiotherapy (n=12) and failure of octreotide treatment (n=15),followed between 2007 and 2010 in Beijing Tiantan Hospital were included in this study.All patients received 1- to 2-months of the long-acting octreotide formulation treatment after the above combination of treatment.Paired samples t-test was used to analysis the variables.Results After two-month duration of the long-acting octreotide formulation treatment,the mean serum free or unbound thyroxine (FT4) ((16.02±1.72) pmol/L) and free triiodothyronine (FT3) ((2.87±0.43) pmol/L) levels of 15 patients significantly decreased compared with those after octreotide-treatment (FT4,(35.36±7.42) pmol/L,P ＜0.001; FT3,(17.85±7.22) pmol/L,P ＜0.001 ).Mean TSH levels stayed in the normal range after the long-acting octreotide formulation treatment ((0.72±0.21) mU/L) and were significantly lower than the pretreatment value ((5.27±1.04) mU/L,P ＜0.001),post-surgery value ((3.37±0.31) mU/L,P ＜0.001 ) and post-octreotide-treatment value ((4.52±0.41) mU/L,P ＜0.001).In these patients with TSH-secreting pituitary adenomas there was no evidence of tachyphylaxis.Conclusion The long-acting octreotide formulation may be a useful and safe therapeutic tool to facilitate the medical treatment of TSH-secreting pituitary adenomas in patients who underwent incomplete surgery or need long-term somatostatin analog therapy.