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Morphological effects of octreotide on growth hormone-producing pituitary adenomas
S Ezzat1, E Horvath, A G Harris
1Department of Medicine, University of Toronto, Ontario, Canada.
Abstract:
The SRIH analog octreotide is a potent GH-inhibiting agent that has been used to effectively treat patients with acromegaly. To investigate the morphological changes induced by octreotide on GH-producing pituitary tumors, we examined 86 adenomas from acromegalic patients who participated in a multicenter study. GH- producing pituitary adenomas removed from 43 patients treated preoperatively with octreotide for 4 months were compared to those obtained from 43 untreated acromegalic patients. Tissue samples were studied by histology, immunohistochemistry, and transmission electron microscopy as well as light microscopic and ultrastructural morphometry. The morphological appearance of some tumors was unaltered by octreotide treatment. Necrotic changes were not apparent in any. Acidophilia and GH immunoreactivity were more pronounced in the octreotide-treated tumors. Perivascular and interstitial fibrosis was more prevalent in the octreotide group (72% vs. 42%). An increase in hormone granularity was obvious in 4 of 15 densely granulated and 2 of 9 sparsely granulated (SG) tumors from treated patients. A decrease in cell size was conspicuous in 4 of 15 densely granulated and 2 of 10 SG adenomas. There was a slight downward trend in the cell and cytoplasmic size in all treated tumors and a slight upward trend in secretory granule size in treated SG adenomas. Only 2 of 9 SG adenomas in the octreotide group, however, demonstrated a statistically significant reduction in cell and cytoplasmic size. There was no statistically significant change in the size of nuclei, secretory granules, or lysosomes between the 2 groups. Decreased cell size and increased granularity were not linked, however. We conclude that there are no striking morphological alterations in GH pituitary adenomas that can be consistently associated with octreotide treatment.
Insights
Octreotide, a growth hormone (GH)-inhibiting agent, showed no significant morphological changes in GH-producing pituitary adenomas. While some minor alterations like increased fibrosis and granularity were observed, they were not consistently linked to treatment.
Area of Science:
- Endocrinology
- Oncology
- Pathology
Background:
- Acromegaly is characterized by excessive growth hormone (GH) production, often from pituitary adenomas.
- Octreotide, a somatostatin analog, is a GH-inhibiting agent used in acromegaly treatment.
- Understanding treatment-induced morphological changes in pituitary adenomas is crucial for assessing therapeutic efficacy.
Purpose of the Study:
- To investigate the morphological alterations in GH-producing pituitary adenomas after preoperative octreotide treatment.
- To compare histological and ultrastructural features of adenomas from treated versus untreated acromegalic patients.
Main Methods:
- Analysis of 86 pituitary adenomas from acromegalic patients (43 treated with octreotide, 43 untreated).
- Utilized histology, immunohistochemistry, transmission electron microscopy, and morphometry.
- Compared morphological features including cell size, granularity, fibrosis, and immunoreactivity.
Main Results:
- Octreotide treatment did not induce striking or consistent morphological changes in GH-producing pituitary adenomas.
- Increased perivascular/interstitial fibrosis and GH immunoreactivity were more prevalent in treated tumors.
- Minor trends observed included increased hormone granularity and decreased cell size in some treated adenomas, but these were not statistically significant across all cases.
Conclusions:
- Octreotide treatment does not lead to significant, consistent morphological alterations in GH-producing pituitary adenomas.
- Observed changes like increased fibrosis and granularity are not definitively linked to octreotide's therapeutic mechanism at the morphological level.
- Further research may be needed to elucidate subtle treatment effects on pituitary adenoma morphology.