Secretion of Human Growth Hormone and Insulin in Levodopa Test during Carbamazepine Therapy

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Abstract
The effect of oral administration of carbamazepine for a period of 3 wk on serum growth hormone, serum immunoreactive insulin [IRI] and blood glucose was studied in healthy volunteers using a L-dopa stimulation test. Serum growth hormone rose significantly from 1.3 .+-. 0.3 ng/ml to 16.3 .+-. 3.4 ng/ml in 60 min after L-dopa administration (1000 mg orally) before carbamazepine, and almost similarly from 2.3 .+-. 0.5 ng/ml to 15.1 .+-. 4.0 ng/ml after carbamazepine during the test. No consistent changes were found in blood glucose concentrations in the L-dopa test before or after carbamazepine. Levels of serum IRI were also normal throughout the test and no impairment in insulin secretion was seen during carbamazepine treatment. Carbamazepine probably does not lead to an altered anterior pituitary function or to an impairment in insulin secretion. This is of advantage when growing children or subjects with a risk factor for diabetes are treated. [Phenytoin, another anti-epileptic agent, has been reported to cause hyperglycemia and impairment of insulin secretion.].