Estimation of urinary aldosterone using thin-layer chromatography and fluorimetry

Area of Science:

• Biochemistry
• Clinical Chemistry
• Endocrinology

Background:

• Aldosterone is a key hormone in regulating blood pressure and electrolyte balance.
• Accurate measurement of urinary aldosterone is crucial for diagnosing conditions like hyperaldosteronism.

Purpose of the Study:

• To develop and validate a fluorimetric assay for urinary aldosterone.
• To establish reference ranges for 24-hour and overnight urine samples.
• To evaluate the utility of overnight urine samples for detecting hyperaldosteronism.

Main Methods:

• Hydrolysis of aldosterone conjugates followed by oxidation.
• Thin-layer chromatography on silica gel.
• Fluorescence detection using sulfuric acid on the chromatogram.

Main Results:

• A linear correlation was observed between aldosterone levels and chromatogram peak area.
• The method demonstrated good intra-assay (4.4%) and inter-assay (6.8%) precision.
• Mean aldosterone excretion was 15.7 nmol/24 hours and 2.6 nmol/8 hours (overnight).
• Elevated aldosterone levels were detected in patients with primary and secondary aldosteronism.

Conclusions:

• The developed fluorimetric technique offers an accurate method for urinary aldosterone assay.
• Overnight urine collections are a viable and effective alternative to 24-hour collections for diagnosing hyperaldosteronism.