Insulinlike growth factor binding proteins and tumor hypoglycemia
1Metabolic Unit, Department of Medicine, University Hospital, CH-8091 Zürich, Switzerland.
Trends in Endocrinology and Metabolism: TEM
|March 1, 1995
Summary
Nonislet cell tumor hypoglycemia is a rare metabolic disorder linked to tumors overproducing insulin-like growth factor (IGF) II. This leads to enhanced IGF II bioavailability, causing low blood sugar despite normal IGF II levels.
Area of Science:
- Endocrinology
- Metabolic Disorders
- Oncology
Background:
- Nonislet cell tumor hypoglycemia is a rare metabolic disorder.
- Pathogenesis is poorly understood due to limited analytic methods.
- It is increasingly recognized as a paraneoplastic syndrome.
Purpose of the Study:
- To elucidate the pathogenetic mechanisms of hypoglycemia in nonislet cell tumors.
- To identify the role of insulin-like growth factor (IGF) II propeptide.
- To explain the discrepancy between tumor IGF II secretion and serum IGF II levels.
Main Methods:
- Analysis of serum insulin and IGF II levels.
- Investigation of IGF II propeptide and mature IGF II.
- Assessment of IGF binding protein complexes and IGF II bioavailability.
Main Results:
- Tumors oversecrete unprocessed (big) IGF II propeptide.
- Negative feedback suppresses mature IGF II production.
- Altered distribution within IGF binding protein complexes enhances IGF II bioavailability.
- Serum IGF II RIA values remain within normal limits, masking the condition.
Conclusions:
- Nonislet cell tumor hypoglycemia is caused by enhanced IGF II bioavailability.
- Tumor-derived big IGF II propeptide drives the disorder.
- The condition is a paraneoplastic syndrome with unique IGF II regulatory mechanisms.
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