Rapid Re-expansion of a Macroprolactinoma After Early Discontinuation of Bromocriptine Bromocriptine Withdrawal and Tumor Re-expansion Orrego et al.

Abstract. Prolactin (PRL)-secreting pituitary adenomas are the most common functioning pituitary tumors. Medical treatment with dopamine agonists is the therapy of choice for macroprolactinomas ($10 mm). Withdrawal of bro-mocriptine after weeks or months of uninterrupted therapy has been associated with rapid tumor re-expansion as evi-denced by x-ray and CT scanning of the pituitary region. We report a patient with a giant macroprolactinoma who had a dramatic response to bromocriptine (tumor volume shrink-age of 53 % within a month) but rapid re-expansion to its original dimensions one week after discontinuation of bro-mocriptine. To our knowledge, this is the first time that the rapid shrinkage/re-expansion of a macroprolactinoma has been documented with serial MRI scans