Evaluation of Endocrine Tests. C: glucagon and clonidine test in phaeochromocytoma.

BACKGROUND: The diagnosis of phaeochromocytoma is based on the demonstration of catecholamine excess. Urine and plasma metanephrine measurements are highly sensitive tests for the diagnosis of phaeochromocytoma, but moderate elevations in metanephrines lack optimal specificity. In this study we aimed to evaluate the diagnostic value of additional tests, i.e. glucagon stimulation and clonidine suppression test, in patients with moderately elevated catecholamines and/or metanephrines. METHODS: Patients with suspected phaeochromocytoma with moderately elevated catecholamines and/or metanephrines in plasma or urine were subjected to the glucagon stimulation and clonidine suppression test. The presence of phaeochromocytoma was confirmed by histology and the absence by a disease-free extended follow-up. RESULTS: Fifty-five patients were included. Phaeochromocytoma was diagnosed in 11 patients. The follow-up period in patients without phaeochromocytoma was 56 (19 to 154) months. The sensitivity of the glucagon test was 30% and the specificity 100%. The clonidine test had no discriminative power, because the area under the ROC curve was not significantly different from 0.5. CONCLUSION: The clonidine suppression test without normetanephrine measurements and the glucagon stimulation test are not sensitive enough to safely exclude phaeochromocytoma in patients with mildly elevated plasma or urine catecholamines.

Establishment of reference values for endocrine tests. III: Primary aldosteronism.

BACKGROUND: In our laboratory well-defined reference values for the screening test and confirmation test used in the diagnosis of primary aldosteronism were lacking. In this study we established the reference-values of the plasma aldosterone concentration (PA), plasma renin activity (PRA) and PA/PRA ratio after a two-hour upright period, and of the urinary aldosterone excretion after oral sodium loading. METHODS: Fifty healthy volunteers, equally distributed according to sex and aged between 20 and 70 years, went through the screening and confirmation test of primary aldosteronism. PA, PRA and the PA/PRA ratios were measured after a two-hour upright period (screening test). Urinary aldosterone excretion was determined in two 24-hour urine samples after an oral suppletion of 6 g NaCl a day for five days (confirmation test). RESULTS: The following reference values were established: PA (after two-hour upright position) <0.03-1.05 nmol/l (mean: 0.47), PA/PRA ratio 0.05-0.47 (mean: 0.15) and urinary aldosterone excretion after sodium loading <3.0-47.0 nmol/24h (mean: 10.5). PRA showed a significant decrease with advancing age: median values in the 3rd to 7th decade are 3.9, 3.5, 2.5, 1.6 and 2.1 ng A1/ml/h respectively (p=0.04). PA was lower in subjects > or = 50 years old. Age did not affect the PA/PRA ratio or the urinary aldosterone excretion. There were no significant differences between the sexes in any of the above-mentioned parameters. CONCLUSION: In this study we established reference values for the screening and confirmation test used in the diagnosis of primary aldosteronism.