Pharmacologic Resistance in Prolactinoma Patients

Pituitary. 2005;8(1):43-52. doi: 10.1007/s11102-005-5085-2.

Abstract

Pharmacologic resistance to dopamine agonists is defined here as failure to normalize PRL levels and failure to decrease macroprolactinoma size by >or=50%. Failure to normalize PRL levels is found in about one-quarter of patients treated with bromocriptine and 10-15% of those treated with pergolide or cabergoline. Failure to achieve at least a 50% reduction in tumor size occurs in about one-third of those treated with bromocriptine and 10-15% of those treated with pergolide or cabergoline. The cause of dopamine resistance is primarily a decrease in D(2) receptors but the receptors have normal affinity for dopamine. Treatment approaches for patients resistant to dopamine agonists include changing to another dopamine agonist and increasing the dose of the drug as long as there is continued response to the dose increases and no adverse effects with higher doses. Transsphenoidal surgery is also an option. Clomiphene, gonadotropins, and GnRH can be used if fertility is desired. For those not desiring fertility, estrogen replacement may be used unless there is a macroadenoma, in which case control of tumor growth is also an issue and dopamine agonists are generally necessary. In many patients modest or even no reduction in tumor size may be acceptable as long as there is not tumor growth. Hormone replacement (estrogen or testosterone) may cause a decrease in efficacy of the dopamine agonist so that it must be carried out cautiously. Reduction of endogenous estrogen, use of selective estrogen receptor modulators, and aromatase inhibitors are potential experimental approaches.

Publication types

  • Review

MeSH terms

  • Bromocriptine / pharmacology
  • Bromocriptine / therapeutic use
  • Cabergoline
  • Cell Proliferation / drug effects
  • Dopamine Agonists / pharmacology
  • Dopamine Agonists / therapeutic use*
  • Dose-Response Relationship, Drug
  • Drug Resistance
  • Ergolines / pharmacology
  • Ergolines / therapeutic use
  • Estrogens / therapeutic use
  • Female
  • Humans
  • Male
  • Pergolide / pharmacology
  • Pergolide / therapeutic use
  • Pituitary Neoplasms / chemistry
  • Pituitary Neoplasms / drug therapy*
  • Pituitary Neoplasms / pathology
  • Prolactin / metabolism
  • Prolactinoma / chemistry
  • Prolactinoma / drug therapy*
  • Prolactinoma / pathology
  • Receptors, Dopamine D2 / analysis
  • Receptors, Dopamine D2 / drug effects

Substances

  • Dopamine Agonists
  • Ergolines
  • Estrogens
  • Receptors, Dopamine D2
  • Pergolide
  • Bromocriptine
  • Prolactin
  • Cabergoline