Study of insulin metabolism in hyperthyroid patients.

Hyperthyroidism is associated with degradation of carbohydrate metabolism. The insulin metabolism in 12 hyperthyroid patients is compared with 10 control subjects. The patients were connected to an artificial beta cell (Biostator GCIIS Miles) for two hours of insulin infusion (40 mU/m2/mn) while glycemia was maintained at its basal level by a modulated glucose infusion. Blood samples were taken, every 15 minutes for insulin and C peptide dosage. In control subjects the insulin steady state level was 93.3 +/- 5 microU/ml whereas this ranged from 42 +/- 3.4 microU/ml to 68 +/- 3.9 microU/ml in hyperthyroid patients. After treatment the insulin level was not quite normal, and ranged from 52 +/- 4.8 microU/ml to 82.2 +/- 9 microU/ml. A glucose intake not corresponding to the same insulin steady state is not therefore to be interpreted. Here there is no evidence of a correlation between the percentage decrease in the insulin test level and the thyroid hormone levels. An impairment of insulin metabolism is suggested in hyperthyroid patients, which might contribute to the decrease in carbohydrate tolerance.