Abnormal proinsulin levels in thyroid dysfunction measured by a sensitive proinsulin immunochemiluminoassay

Area of Science:

• Endocrinology
• Metabolic Disorders

Background:

• Abnormalities in carbohydrate metabolism are common in hyperthyroid patients.
• Elevated proinsulin levels serve as an early indicator of B-cell impairment.
• Previous studies noted decreased proinsulin in hyperthyroid patients post-therapy and limited data on hypothyroid patients.

Purpose of the Study:

• To investigate the changes in proinsulin levels in hypothyroid patients after thyroxine therapy.
• To confirm the effect of antithyroid therapy on proinsulin levels in hyperthyroid patients.
• To establish the correlation between thyroid function and B-cell function.

Main Methods:

• Utilized a newly developed, sensitive immunochemiluminometric assay for proinsulin measurement.
• Measured basal fasting proinsulin levels in hypothyroid patients before and after thyroxine therapy (n=7).
• Measured proinsulin levels in hyperthyroid patients before and after methimazole therapy (n=12).

Main Results:

• Proinsulin levels significantly increased in hypothyroid patients following thyroxine therapy (4.2 +/- 2.4 vs. 10.0 +/- 5.6 pmol/L, p < 0.05).
• Proinsulin levels significantly decreased in hyperthyroid patients after methimazole therapy (27.8 +/- 26.0 vs. 15.8 +/- 15.7 pmol/L, p < 0.05).

Conclusions:

• Thyroid hormone status directly influences B-cell function, as reflected by proinsulin levels.
• Thyroxine therapy normalizes suppressed proinsulin levels in hypothyroidism.
• Antithyroid therapy effectively reduces elevated proinsulin levels in hyperthyroidism.