Insulin metabolism in hypothyroidism

Area of Science:

• Endocrinology
• Metabolic Research

Background:

• Glucose intolerance is a common observation in hypothyroid patients.
• Insulin resistance has been proposed as the underlying mechanism for this glucose intolerance.

Purpose of the Study:

• To investigate whether insulin resistance contributes to glucose intolerance in hypothyroid patients.
• To compare insulin pharmacokinetics and glucose-lowering effects in hypothyroid, normal, and treated euthyroid individuals.

Main Methods:

• Intravenous administration of porcine insulin (0.1 U./kg.) to ten hypothyroid patients, ten normal subjects, and six treated euthyroid patients.
• Measurement of serum immunoreactive insulin concentrations, insulin half-life, distribution space, and fractional/metabolic clearances.
• Monitoring of plasma glucose concentrations over time post-insulin administration.

Main Results:

• Serum insulin levels and insulin clearances were comparable across all three groups.
• Hypothyroid patients experienced a prolonged decrease in plasma glucose levels after insulin administration compared to controls.
• The hypoglycemic effect of exogenous insulin was more sustained in hypothyroid patients.

Conclusions:

• There is no evidence of insulin resistance in hypothyroid patients.
• Hypothyroid patients may exhibit increased sensitivity to insulin action.
• Glucose intolerance in hypothyroidism is not attributable to insulin resistance.