Urinary Steroids Measured by Modern Separation Techniques and Applied as Biomarkers in Stress Studies

Ilona      Oledzka; Tomasz      Baczek

Abstract

A biomarker is a measure of the interaction occurring in the biological systems between the organism and the potential risks that may be of chemical, physical, or biological character. The measured response of the body caused by this interaction can be of physiological, functional or biochemical character and can be captured at the cellular or molecular level.

Steroids, especially cortisol and cortisone, are valuable biomarkers serving primarily the assessment of the organisms reaction to exposure to chronic stress. The problem of stress and its impact on the development of endocrinological, metabolic, psychiatric and cardiovascular diseases has been the subject of intense research for some years. Studies on cortisol and cortisone in biological materials such as serum, plasma, urine, or saliva were applied to measure stress levels in the body. The advantage of urine-based measurements lies in non-invasive nature of the method of sampling. The serum cortisol and cortisone levels may be increased in certain disease states such as diabetes, obesity, hyperthyroidism, and in pregnancy. Therefore, measurement of free cortisol in urine is the most reliable way to diagnose either stress disorder, or the functioning of the hypothalamic-pituitary-adrenal (HPA) axis.

In the review, several validated high-performance liquid chromatography (HPLC) and micellar electrokinetic capillary chromatography (MECC) assays for determination of steroids in urine samples were compared. Because these methods are automated, simple, rapid, and sensitive, they can be applied easily to the analysis of urine samples. However, HPLC is sometimes limited in its separation efficiency, and the consumption of organic solvents is relatively high. On the other hand, the important drawback of MECC is that sometimes it cannot be sensitive enough to determine low concentrations, e.g., when the sample injection volume is low and the optical path-length short. Nevertheless, it finally seems that MECC offers greater separation efficiency than HPLC and significantly reduces the analysis time and the operating costs compared to HPLC.

In summary, those methods carry a great analytical potential, especially because urine, used as biological matrix and treated as a biological fluid, is easy to obtain in non-invasive collection procedures.

Keywords: Urine, Biomarkers, Steroid hormones, Stress studies, High-performance liquid chromatography (HPLC), Micellar electrokinetic capillary chromatography (MEKC)