Normal insulin levels
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Understanding Normal Insulin Levels: Insights from Recent Research
Normal Insulin Levels in Healthy Individuals
Basal Insulin Levels in Healthy Adults
Basal insulin levels are crucial for maintaining normal blood glucose levels. In healthy individuals, basal insulin levels are typically around 0.2 units per kilogram per day (U/kg/d) when near-normal glycemia is achieved through continuous subcutaneous insulin infusion or once-nightly basal insulin. This dosage helps to normalize fasting plasma glucose (FPG) levels while avoiding significant hypoglycemia.
Insulin Levels in Pre-Pubertal Children
In pre-pubertal children, insulin levels vary with age and sex. Median serum insulin levels range from 17.4 pmol/L in 3- to 3.5-year-old girls to 53.5 pmol/L in 10.5- to 11-year-old girls. Boys of the same age groups have slightly lower median insulin levels, ranging from 13.2 pmol/L to 43.0 pmol/L. These values provide a reference for normal insulin levels in children and highlight the continuous increase in insulin levels with age.
Insulin Levels During Pregnancy
During pregnancy, insulin levels in amniotic fluid increase significantly. Between the 13th and 25th weeks of gestation, insulin levels rise from an average of 1.3 to 5.1 µU/ml. This increase continues from the 27th to the 42nd weeks, reaching levels between 6 and 9.1 µU/ml. These levels are essential for fetal development and indicate normal insulin transfer via fetal urine.
Insulin Response to Exogenous Administration
Serum Insulin Levels Post-Insulin Injection
After the administration of exogenous insulin, serum insulin levels peak at different times depending on the type of insulin used. For instance, after injecting 10 units of regular insulin subcutaneously, the peak serum insulin concentration is approximately 26.2 µU/ml at 60 minutes. In contrast, NPH insulin peaks between 2 and 9 hours post-injection, with the peak level correlating with the dose administered. This variability underscores the challenge in maintaining normal blood sugar levels in insulin-deficient diabetic patients.
Insulin Sensitivity and Resistance
Insulin Sensitivity Indices
Insulin sensitivity can be assessed using indices calculated from basal and oral glucose tolerance test (OGTT)-induced insulin, glucose, and free fatty acid (FFA) levels. The Insulin Sensitivity Index for glycemia (ISI(gly)) and blood FFA (ISI(ffa)) are around 1 in normal subjects, with variations between 0 and 2. These indices are reduced in overweight individuals, those with impaired glucose tolerance (IGT), and non-insulin-dependent diabetes mellitus (NIDDM) patients. This reduction indicates decreased insulin sensitivity in these populations.
Impairment in Beta-Cell Function
In obese youth with normal glucose tolerance, increased 2-hour plasma glucose levels are associated with a specific impairment in beta-cell responsiveness, independent of insulin sensitivity. This impairment is evident even when the 2-hour plasma glucose levels are within the normal range, suggesting a continuum of risk for developing type 2 diabetes mellitus.
Conclusion
Understanding normal insulin levels and their variations across different populations and conditions is essential for managing and diagnosing metabolic disorders. Basal insulin levels, insulin response to exogenous administration, and insulin sensitivity indices provide valuable insights into normal and impaired insulin function. These findings highlight the importance of tailored insulin therapy and monitoring to maintain optimal glucose levels and prevent complications.
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