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Carcinoids are neuroendocrine tumors. They produce physiologically active substances which can cause carcinoid syndrome and carcinoid heart disease at higher concentrations. The char­acteristic changes seen in carcinoid heart disease are carcinoid endocardial plaques. The pathogenesis of carcinoid heart disease is not completely understood. An attempt was made to show the differences in biochemical markers between two groups of patients: those with carcinoid heart disease and those without it. Through these differences we hoped to get some insight into the pathogenesis of carcinoid heart disease and to be able to verify the diagnostic value of these biochemical markers. One of the objectives was also to calculate the incidence of carcinoid heart disease in patients with carcinoid syndrome in Slovenia.

Our hypotheses were as follows: 1. Levels of chromogranin A, 5-HIAA and TGF-P1 will be significantly higher in the group with carcinoid heart disease compared to the control group. 2. Concentrations of 5-HIAA before treatment with octreotide will be significantly higher in the group with carcinoid heart disease compared to the control group. 3. Treatment with octreotide will not prevent the appearance of carcinoid heart disease. The study was prospective and included all patients in Slovenia who were diagnosed with and treated for carcinoid syndrome at the time. They were divided into two groups based on echocardio- graphic findings typical for carcinoid heart disease. Serum concentrations of chromogranin A were measured using RIA, urinary concentrations of 5-HIAA were measured using HPLC, and serum concentrations of TGF-P1 were measured using ELISA. Nonparametric tests were used for statistical analysis.

The most common echocardiographic finding in the group with carcinoid heart disease was tricuspid regurgitation with morphologic changes of the tricuspid valve. The group with carcinoid heart disease had significantly higher concentrations of chromogranin than the con­trol group. The correlation between serum concentrations of chromogranin A and urinary concentrations of 5-HIAA was statistically significant during for the period before treatment with octreotide and for the period when control measures were made. Differences in 5-HIAA concentrations between the two groups were statistically significant only for the peri­od when control measures were made, but not for the period before treatment. The decrease in urinary concentrations of 5-HIAA after treatment was not statistically significant and nei­ther were differences in the serum concentrations of TGF-P1. The incidence of carcinoid heart disease did not depend on the duration of symptoms of carcinoid syndrome. Serum con­centrations of chromogranin A and urinary concentrations of 5-HIAA were found to be useful in the diagnostics and follow-up of patients with carcinoid syndrome and carcinoid heart dis­ease. The levels of 5-HIAA established in our study indicate an important role of serotonin in the pathogenesis of carcinoid plaques. Treatment with octreotide does not cause a significant decrease in the 5-HIAA concentrations and has no impact on the appearance of carcinoid heart disease. Serum concentrations of TGF-P1, on the other hand, were not found to be help­ful in the diagnostics of carcinoid syndrome or carcinoid heart disease.