Although several authors have previously shown that circulating anti-insulin antibodies do affect the pharmacokinetics and pharmacodynamics of injected insulin (14), Heise et al. (5) were unable to show this effect in relation to the increase in anti-insulin antibodies induced by inhaled insulin. Heise et al., however, have applied a study design based on the questionable method of the euglycemic clamp (5), which had been criticized before because of its potential imprecision in demonstrating the biological effects of exogenous insulin (6). This method had not been used in the earlier studies (14), which, however, had reported serum free insulin levels (Heise et al. failed to do so). I wonder if the determination of serum free insulin levels would help to explain the apparent discrepancy between the data reported by Heise et al. (5) and those of the previous studies (14)?

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