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. Chin Med J 2012;125(15):2758-2763