Endocrine Abstracts

JOINT3884

Introduction: Giant macroprolactinomas are rare pituitary tumors that can present with atypical radiological features, sometimes mimicking craniopharyngiomas. While dopamine agonist therapy typically leads to significant tumor shrinkage and normalization of prolactin levels, persistent hyperprolactinemia despite radiological resolution may indicate macroprolactinemia, particularly due to Big Big Prolactin (1).

Case Presentation: We present the case of a 27-year-old male with progressive visual disturbances, headaches, and hypopituitarism. MRI revealed a large sellar and suprasellar mass with cystic components and calcifications, initially suggestive of a craniopharyngioma. However, markedly elevated prolactin levels (300 ng/ml) led to the diagnosis of a giant macroprolactinoma. Due to significant visual impairment, surgical intervention was performed, followed by cabergoline therapy (2 mg weekly). After two years, complete radiological tumor resolution was achieved, with no clinical signs of hyperprolactinemia. Despite this, prolactin levels remained elevated (170 ng/ml), prompting further analysis. Polyethylene glycol (PEG) precipitation confirmed the presence of Big Big Prolactin, a high-molecular-weight prolactin complex with reduced bioactivity (2,3). After confirmation, cabergoline was gradually tapered and discontinued.

Conclusion: This case underscores the importance of distinguishing true hyperprolactinemia from macroprolactinemia in patients with persistent hyperprolactinemia despite tumor resolution. Recognizing the Big Big Prolactin phenomenon can prevent unnecessary treatment continuation and misinterpretation of disease activity. Systematic screening for macroprolactinemia should be considered in similar cases to optimize patient management (4).

References: 1. Hattori N. Macroprolactinemia: a new cause of hyperprolactinemia. J Endocrinol Invest. 2014. Link.

2. Sinha YN. Prolactin variants in human serum. Endocr Rev. 1995. Link.

3. Glezer A, Bronstein MD. Approach to the patient with persistent hyperprolactinemia and negative sellar imaging. J Clin Endocrinol Metab. 2006. Link.

4. Kasperlik-Załuska AA, Czarnocka B, Jeske W. Macroprolactinemia in patients with pituitary adenomas. Neuro Endocrinol Lett. 2011. Link.