Beneficial Effects of High Doses of Cabergoline in the Treatment of Giant Prolactinoma Resistant to Dopamine Agonists: A Case Report with a 21-Year Follow-Up

Introduction: Prolactinomas are pituitary tumors with a very low prevalence in childhood and adolescence compared to adulthood. This condition is preferentially treated with dopamine agonists. Resistance to these drugs is rare. Case Report: We describe the case of a boy diagnosed with mac-roadenoma at the age of 9 and followed up for 21 years. He did not fully respond to treatment with dopamine agonists. His initial prolactin level was 2,400 ng/mL (in males, normal values are <16.0 ng/mL) and never normalized. At the last assessment, his prolactin level was 21.5 ng/mL, recorded after 21 years of treatment with the dopamine agonist cabergoline at a dose as high as 4.5 mg per week. Although the prolactin level remained elevated throughout the follow-up period, the patient never presented a low testosterone level and had normal pubertal development. An MRI of the sella turcica showed that the tumor became progressively cystic and disappeared, but a normal pituitary gland was observed. The pituitary gland retained its normal functions despite a partially empty sella. Discussion: Long-term treatment with high doses of cabergoline may cause cystic degeneration of a prolactinoma considered to be resistant to this treatment, but we cannot rule out the possibility that this outcome represents the natural development of the tumor. (C) 2017 S. Karger AG, Basel