Giant pituitary prolactinoma with falsely low serum prolactin: the pitfall of the "high-dose hook effect": case report.

Abstract

OBJECTIVE AND IMPORTANCE:

We present a case of a giant prolactinoma with a falsely low serum prolactin concentration determined by a two-site chemiluminometric assay. Awareness of the possibility of the "high-dose hook effect" in such cases will prevent preoperative misdiagnosis.

CLINICAL PRESENTATION:

A patient with a giant invasive pituitary tumor was found preoperatively to have serum prolactin of 31 ng/ml. Pathological examination of the excised tissue, however, demonstrated strong staining for prolactin.

INTERVENTION:

Serial dilutions of the serum disclosed hyperprolactinemia of 280,000 ng/ml, establishing the presence of the "high-dose hook effect." Treatment with pergolide (Permax; Athena Neurosciences, S. San Francisco, CA) decreased tumor size and lowered serum prolactin by more than 99%.

CONCLUSION:

A "high-dose hook effect" needs to be suspected in every patient with a giant pituitary adenoma (>3 cm) and normal serum prolactin. Subsequently assaying the diluted serum will reliably disclose this phenomenon and allow correct diagnosis and therapy.

• Authors: A L Barkan, W F Chandler
• Journal: Neurosurgery (Neurosurgery) Vol. 42 Issue 4 Pg. 913-5; discussion 915-6 (Apr 1998) ISSN: 0148-396X [Print] United States
• PMID: 9574657 (Publication Type: Case Reports, Journal Article)

Chemical References

• Dopamine Agonists
• Pergolide
• Prolactin

Topics

• Adult
• Dopamine Agonists (therapeutic use)
• Humans
• Luminescent Measurements
• Magnetic Resonance Imaging
• Male
• Pergolide (therapeutic use)
• Pituitary Neoplasms (blood, drug therapy, surgery)
• Prolactin (blood)
• Prolactinoma (blood, drug therapy, surgery)