| Abstract: | We described a 12 7/12-year-old boy presenting the syndrome of insulin resistance and acanthosis nigricans Type A. Insulin levels at fasting state and after glucose loading were 149 +/- 63 microunits/ml (mean +/- SD) and over 1000 microunits/ml, respectively, while fasting levels of blood glucose were 77.7 +/- 8.9 mg/dl (mean +/- SD). A marked resistance to exogenous insulin was observed. Circulating levels of insulin antagonists such as growth hormone, cortisol and glucagon, were within the normal range. Proinsulin was less than 5% of the total radioimmunoassayable insulin. Insulin antibody and anti-receptor antibody were not detected. Insulin binding to mononuclear cells were decreased to about 50% of controls. Analysis of membrane receptors demonstrated the normal average affinity, dissociation kinetics and negative cooperativity with a decreased number of receptors. After two days fasting, plasma IRI levels decreased to 27 microunits/ml, however insulin binding kinetics were not affected. This might suggesting that the receptor decrease was not secondary to hyperinsulinemia. These findings indicate that a decreased number of receptors was one of the causes for insulin resistance in the patient. |
