Bromocriptine treatment reduces the cell size in human macroprolactinomas: a morphometric study

Area of Science:

• Endocrinology
• Pathology
• Oncology

Background:

• Macroprolactinomas are pituitary tumors that secrete prolactin (PRL).
• Bromocriptine (Brc) is a dopamine agonist used to treat macroprolactinomas, leading to reduced serum PRL levels and tumor size.
• The precise cellular mechanisms underlying Brc-induced tumor shrinkage require further investigation.

Purpose of the Study:

• To investigate the morphological changes in macroprolactinomas after bromocriptine (Brc) treatment.
• To compare the cellular structure of macroprolactinomas from untreated patients versus those treated with Brc.

Main Methods:

• Surgical removal of macroprolactinomas from untreated and Brc-treated patients.
• Application of light microscopy, immunofluorescence microscopy, and electron microscopy.
• Utilizing electron microscopic morphometry for quantitative analysis.

Main Results:

• Bromocriptine treatment led to significant reductions in macroprolactinoma cell size, with greater cytoplasmic shrinkage than nuclear shrinkage.
• Electron microscopy revealed involution of the rough endoplasmic reticulum and Golgi complex in Brc-treated tumors.
• Increased numbers of secretory granules were observed in some Brc-treated tumors, with no difference between short-term and long-term treatment.

Conclusions:

• Bromocriptine induces significant cellular shrinkage in macroprolactinomas, likely by affecting the endoplasmic reticulum and Golgi apparatus.
• This Brc-induced reduction in cell size contributes to the overall tumor size reduction observed clinically.
• The morphological effects of Brc on macroprolactinomas are evident after 6 weeks of treatment and persist up to 1 year.