"Invasive giant prolactinoma" is a large prolactinoma (>4 cm in dimension) presenting with serum prolactin levels of >1000 ng/dL and mass related clinical symptoms. Here we report a patient with a giant prolactinoma presented with central hypogonadism, suppressed adrenal and thyroid function, supra sellar extension, visual field impairment and high prolactin level.The patient was treated with cabergoline, levothyroxin and prednisolone. After 18 months, tumor size markedly reduced, associated with adrenal function and visual field improvement, but central hypogonadism and secondary hypothyroidism persisted.Previous studies showed normalization of thyrotropin secretion after treatment but it remained low in our patient even after 18 months follow up.