Growth hormone (GH) and thyroid stimulating hormone (TSH)-secreting pituitary adenomas are very rare and they account for only 0.5% for all pituitary adenomas. These adenomas are usually treated with surgery, but this surgery is not easy because the tumor is usually huge and invasive. We reported here on a case of a GH-TSH-secreting adenoma in a 23-year-old male patient who was initially treated with octreotide LAR. He presented with symptoms of headache, palpitation and a visual defect that he had for the 3 months. He had hypertrophy of the frontal bone and enlargement of both the hands and feet. The visual field test showed bitemporal hemianopsia. The laboratory examinations showed high serum levels of free T4, TSH and free alpha-subunit. Additionally, the serum levels of GH and insulin-like growth factor-I (IGF-I) were increased. GH was not suppressed below 1µg/L by an oral 75g glucose loading test, and TSH was not stimulated by thyrotropin-releasing hormone (TRH). Because sellar MRI showed invasive macroadenoma encasing the vessels, we initially tried octreotide LAR for treatment. A year later, the IGF-I and thyroid function tests were normalized and the size of the tumor was reduced with cystic change. The symptoms of palpitation and headache were improved without a change of the visual field defect.