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In vivo responsiveness of morphological variants of growth hormone-producing pituitary adenomas to octreotide
S Ezzat1, G Kontogeorgos, D A Redelmeier
1Department of Medicine, University of Toronto, Canada.
Abstract:
The somatostatin analog, octreotide, is an inhibitor of growth hormone (GH) secretion that has been used to treat patients with GH-producing pituitary tumors. In this study we investigated the in vivo responsiveness to treatment with this analog in patients harboring different morphological types of GH-producing pituitary adenomas. Both GH and insulin-like growth factor I (IGF-I) plasma levels in 30 patients treated with octreotide (300 micrograms/day) for 4 months preoperatively were compared with those from 30 patients who did not receive treatment preoperatively. Tissue samples were studied using ultrastructural and immunohistochemical techniques. Amongst patients harboring densely granulated (DG) adenomas, mean GH levels were reduced to 32 +/- 9% by octreotide, to 30 +/- 7% by surgery and to 26 +/- 9% of baseline by both interventions. Surgery was equally as effective in lowering GH levels in patients with sparsely granulated (SG) adenomas as it was in those with DG adenomas; in patients with SG adenomas, GH levels were reduced by surgery alone to 37 +/- 16% and to 24 +/- 15% when performed following octreotide pretreatment. In contrast, treatment with octreotide alone in patients harbouring SG adenomas reduced GH levels to only 70 +/- 13% of baseline (p < 0.02 compared to surgery alone, or surgery and octreotide). We conclude that the GH inhibitory effects of octreotide are significantly better in patients harboring DG somatotroph adenomas compared with those harboring SG adenomas.
Insights
Octreotide, a growth hormone (GH) inhibitor, effectively reduces GH levels in patients with densely granulated (DG) pituitary adenomas. However, its efficacy is limited in sparsely granulated (SG) adenomas compared to surgery.
Area of Science:
- Endocrinology
- Oncology
- Neurosurgery
Background:
- Growth hormone (GH)-producing pituitary tumors, or adenomas, are a significant clinical challenge.
- Octreotide, a somatostatin analog, is a known inhibitor of GH secretion used in treating these tumors.
- Pituitary adenomas exhibit varying morphological types, potentially influencing treatment response.
Purpose of the Study:
- To investigate the in vivo efficacy of octreotide in patients with different morphological types of GH-producing pituitary adenomas.
- To compare the effects of octreotide treatment, surgery, and a combination of both on GH and IGF-I levels.
- To determine if octreotide's GH inhibitory effects differ between densely granulated (DG) and sparsely granulated (SG) adenomas.
Main Methods:
- A comparative study involving 60 patients with GH-producing pituitary adenomas.
- 30 patients received octreotide (300 micrograms/day) for 4 months preoperatively; 30 served as a control group.
- Plasma GH and IGF-I levels were measured, and tissue samples underwent ultrastructural and immunohistochemical analysis.
Main Results:
- Octreotide significantly reduced GH levels in patients with DG adenomas (32% of baseline).
- In SG adenomas, octreotide alone showed limited efficacy (70% of baseline GH), while surgery was more effective.
- Combined octreotide and surgery yielded similar GH reductions in both DG and SG adenomas.
Conclusions:
- Octreotide demonstrates superior GH inhibitory effects in patients with DG somatotroph adenomas compared to SG adenomas.
- Surgical intervention remains a highly effective treatment for GH reduction in both adenoma types.
- Preoperative octreotide treatment may offer benefits when combined with surgery, particularly in DG adenomas.