An acromegalic patient with nontoxic autonomous goiter was sequentially treated with octreotide and bromocriptine. Before therapy, serum GH, PRL and insulin-like growth factor-I (IGF-I) levels were increased. Free T₃ and free T₄ were within the normal range with suppressed TSH levels, whereas ¹²³Iodine-uptake of thyroid was 5.6% after 24h. During treatment with octreotide and bromocriptine, serum GH, PRL, and IGF-I became normal and free T₃ and free T₄ were slightly but significantly decreased, but TSH levels remained very low. After thyroidectomy, thyroglobulin, free T₃ and free T₄ were further decreased, and the TSH levels were recovered to normal. These findings suggested that octreotide and bromocriptine inhibit the release of thyroid hormones from the autonomous thyroid gland directly or indirectly through the decline in IGF-I.