A 48-year-old female presented with acromegaly, amenorrhea and hyperthyroidism associated with high serum free T4 levels and measurable TSH concentrations. The administration of GHRH induced significant increases in GH, PRL and TSH. Conversely, intravenous infusion of dopamine or oral administration of bromocriptine effectively inhibited GH, PRL and TSH secretion. Serum α-subunit levels were neither affected by GHRH, dopamine nor bromocriptine. Transsphenoidal surgery was performed and immunostaining of the tissue showed that the adenoma cells were positive for GH, PRL or TSH. The patient was treated with bromocriptine at a daily oral dose of 10mg after surgery. Serum TSH were initially suppressed but returned within reference intervals with persistent normalized free T₄ levels. Serum PRL became undetectable and GH levels were stable around 6ng/ml except the periods of poor drug compliance, when serum TSH, GH and PRL levels rose considerably. The patient was followed-up for 10 years without any change in the residual adenoma tissues as detected by magnetic resonance imaging. These findings suggest that long-term bromocriptine therapy is effective in treating the hypersecretory state of a plurihormonal adenoma secreting TSH, GH and PRL.