From the Research
Normal Insulin Levels
- The normal fasting levels of immunoreactive insulin (IRI) have been reported to be around 0.048 +/- 0.009 nM in normal persons 1.
- In another study, the immunoreactive insulin level (IRI) in haemolyzed erythrocytes of normal fasting subjects was 49.2 +/- 3.5 microU/ml, which is approximately 5 times higher compared to the plasma levels of the same subjects 2.
- After an oral glucose load, the IRI levels in normal persons increased to 0.52 +/- 0.077 nM 1.
Comparison of IRI Levels in Different Groups
- Maturity-onset diabetics had higher fasting levels of IRI (0.11 +/- 0.029 nM) compared to normal subjects 1.
- Insulin-requiring diabetics had fasting IRI levels of 0.063 +/- 0.009 nM 1.
- Patients with insulinoma had elevated IRI levels, with one patient having an IRI level of 704 microU.ml-1 during tumor manipulation, which decreased to 9.8 microU.ml-1 after tumor resection 3.
IRI Levels in Response to Different Stimuli
- In normal subjects, the IRI levels increased in response to oral glucose load, with a peak level of 0.52 +/- 0.077 nM 1.
- In patients with organic hyperinsulinism, the IRI levels were inappropriately high for the corresponding blood glucose values, and increased further in response to insulin secretagogues such as glucose, tolbutamide, glucagon, or amino acids 4.