Can Chromatography Help Test Cortisol Levels?
Oct 09 2018
Cortisol is one of the body’s main hormones. Along with adrenaline, cortisol is part of our fight or flight response - but this hormone does so much more than help us run from attack. A recent paper in the Asian Journal of Pharmaceutical and Clinical Research - Measurement of cortisol in human plasma and urine by ultra performance liquid chromatography-tandem mass spectrometry - reports on a new chromatography method that uses internal standards to help in the analysis of cortisol levels in plasma and urine.
Cortisol – receptors everywhere
Cortisol is a steroid hormone in the glucocorticoid class, which in turn are part of the corticosteroid class. Glucocorticoid receptors are found in every cell in the human body - which means that cortisol can be used by any cell in the body. It also works with our brains to control our moods and motivations.
Cortisol is made in our adrenal glands - small organs just above the kidneys - and then released into the blood stream which transports cortisol all around the body. With almost every cell able to capture cortisol, it has many different actions in the body depending on the type of cell it binds to. Metabolism control, anti-inflammatory response, influencing blood pressure and helping women give birth are just some of the roles of cortisol.
The method developed by the scientists in the Middle East uses a new internal standard to help analyse cortisol. The Saudi Arabian researchers report that they have used tolperisone as the internal standard - which they state is more readily available than the tradition internal standard of d-4 cortisol. Tolperisone is a type of muscle relaxant which is readily available and has a low incidence of reactivity with other drugs.
An internal standard, also known as IS, is simply a compound added to both sample and control to allow a better analysis in terms of identification and quantification in chromatography runs. It is easy for small variations in conditions - oven temperature, gas flows, injection technique - to occur between even consecutive chromatography runs. By using an internal standard, these variations can be taken in account and their effects reduced when carrying out the final analysis.
Chromatography hits the mark
The team report that a literature review considers either gas or liquid chromatography to be a more reliable test for cortisol levels in urine and serum than the radioimmunoassay method usually used. However, these GC and LC methods use denatured cortisol as the IS - a substance that is not readily available.
The method they developed using tolperisone as the IS with liquid chromatography in conjunction with tandem mass spectrometry (LC-MS/MS) was successful in determining cortisol in both urine and plasma samples. Developing new chromatography methods is the subject of the article, Using Different HPLC Column Chemistries To Maximise Selectivity For Method Development.
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