高血圧症におけるaldosterone分泌の指標としての尿中3α, 5β-tetrahydroaldosterone測定の意義
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概要
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Aldosterone secretion can be assessed by measurements of plasma aldosterone concentration (PAC), aldosterone metabolic products in urine, and aldosterone secretion rate (ASR). Blood sampling and determination of PAC have practical and methodological advantages, however, plasma aldosterone shows a diurnal variation and several episodic secretory peaks in normal subjects and various forms of hypertension. Methods based on diurnal urinary excretion integrate the aldosterone secretion over a 24 hour period, thereby minimizing the effect of an intermittent secretory burst. Measurements of urinary aldosterone-18-glucuronide (Aldo-18-g), which represents only about 10 percent of the aldosterone metabolites, have been used in most laboratories because of the less complicated methodology. 3α, 5β-tetrahydroaldosterone (3α, 5β-THAldo) isolated from human urine is the most abundant aldosterone metabolite and represents about 35 per cent. 3α, 5β-THAldo formation in the liver is in contrast to the renal and hepatic origin of Aldo-18-g. To determine ASR, radioisotope-labeled aldosterone has to be injected intravenously, and urine has to be collected during the following 24 hours. Therefore, the characteristics of these parameters must be taken into account for assessing aldosterone secretion.<BR>Urinary 3α, 5β-THAldo, PAC and urinary Aldo-18-g excretion were determined in normal subjects, patients with essential hypertension and patients with primary aldosteronism (PA) in basal condition and in the 9α-fluorohydrocortisone (9αFF) suppression test. The relationship between creatinine clearance (Ccr) and aldosterone parameters was studied in the patients with essential hypertension.<BR>1. Urinary 3α, 5β-THAldo excretion or ASR may be suitable parameters for assessing hyperaldosteronism if PAC or urinary Aldo-18-g excretion is within the normal range in basal condition in the patients with PA.<BR>2. The elevation in PAC and the decrease in urinary Aldo-18-g excretion were observed depending on the degree of changes of Ccr in the patients with essential hypertension.<BR>3. The determination of urinary 3α, 5β-THAldo in the 9αFF suppression test proved to be a most useful tool for the diagnosis of PA, while the determination of urinary Aldo-18-g was not a suitable parameter.<BR>From these results the determination of 3α, 5β-THAldo in hypertensive patients might be a suitable way to detect abnormalities of aldosterone secretion, and it should be noted that proper parameters should be selected for assessing the aldosterone secretion in various forms of aldosterone disorders.
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