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Dopamine resistance of prolactinomas
1Division of Endocrinology, Metabolism and Molecular Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA. molitch@northwestern.edu
Pituitary
|December 17, 2003
Summary
Dopamine agonist resistance in pituitary tumors is defined by normalized prolactin (PRL) levels or tumor size reduction. Cabergoline shows higher efficacy than bromocriptine, with various treatment options available for resistant cases.
Area of Science:
- Endocrinology
- Oncology
- Pharmacology
Background:
- Dopamine agonists are primary treatments for prolactinomas.
- Resistance to dopamine agonists is a clinical challenge, impacting treatment efficacy.
- Understanding resistance mechanisms is crucial for optimizing patient management.
Purpose of the Study:
- To define and quantify resistance to dopamine agonists based on prolactin normalization and tumor shrinkage.
- To investigate the characteristics of dopamine agonist-resistant pituitary tumors.
- To explore alternative treatment strategies for patients resistant to dopamine agonists.
Main Methods:
- Defined resistance by failure to normalize PRL levels or achieve >=50% tumor size reduction.
- Compared resistance rates among bromocriptine, pergolide, and cabergoline.
- Analyzed in vitro D2 receptor characteristics of resistant tumors.
- Reviewed treatment options including dose escalation, drug switching, surgery, and fertility-sparing therapies.
Main Results:
- Resistance rates for normalizing PRL: bromocriptine (24%), pergolide (13%), cabergoline (11%).
- Resistance rates for >=50% tumor reduction: bromocriptine (~33%), pergolide (10-15%), cabergoline (10-15%).
- Resistant tumors show decreased D2 receptor number but normal affinity.
- Dopamine agonist dose increase is viable if tolerated and effective; surgery is an option.
Conclusions:
- Cabergoline demonstrates superior efficacy in managing pituitary tumors compared to bromocriptine and pergolide.
- Dopamine agonist resistance is characterized by reduced D2 receptor density.
- Management of resistant cases requires individualized strategies, including alternative medications, surgery, or hormonal therapies, with careful consideration of fertility and tumor growth.