A case of insulin resistance associated with acanthosis nigricans.

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Abstract
A 12 yr old male patient with the syndrome of insulin resistance and acanthosis nigricans type A is described. Insulin levels at fasting state and after glucose loading were 149 .+-. 63 .mu. U/ml (mean .+-. SD) and > 1000 .mu.U/ml, respectively; the fasting level of blood glucose was 77.7 .+-. 8.9 mg/ml. 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 < 5% of the radioimmunoassayable insulin. No insulin antibody or antireceptor antibody was detected. Insulin binding to mononuclear cells was decreased to .apprx. 50% of control. Analysis of membrane receptors demonstrated the normal average affinity, dissociation kinetics and negative cooperativity, with a decreased number of receptors. After 2 days fasting, plasma IRI [immunoreactive insulin] levels decreased to 27 .mu.U/ml, while insulin binding kinetics were not affected; thus, the receptor decrease apparently was not secondary to hyperinsulinemia. The decreased number of receptors was probably one of the causes for insulin resistance in this patient.