A steroid is an organic compound with four rings arranged in a specific molecular configuration. Hundreds of steroids exist. Examples include the dietary lipid cholesterol, the sex hormones estradiol and testosterone and the anti-inflammatory drug dexamethasone. Steroids have two principal biological functions: certain steroids (such as cholesterol) are important components of cell membranes which alter membrane fluidity, and many steroids are signaling molecules which activate steroid hormone receptors.
Steroids and their metabolites often function as signalling molecules. Steroids and phospholipids are components of cell membranes. Steroids such as cholesterol decrease membrane fluidity. Similar to lipids, steroids are highly concentrated energy stores. However, they are not typically sources of energy; in mammals, they are normally metabolized and excreted.
Steroidogenesis is the biological process by which steroids are generated from cholesterol and changed into other steroids. The major classes of steroid hormones are Progestogen, Corticosteroids (corticoids), Androgens, and Estrogens. Steroid metabolism in humans is the target of cholesterol-lowering drugs, such as statins. Steroids are primarily oxidized by cytochrome P450 oxidase enzymes, such as CYP3A4. These reactions introduce oxygen into the steroid ring, allowing the cholesterol to be broken up by other enzymes into bile acids. These acids can then be eliminated by secretion from the liver in bile.
High-performance liquid chromatography (HPLC) is extensively used in steroid analysis to separate steroids prior to mass analysis. Various ESI-MS methods have been developed for analysis of different classes, subclasses, and individual steroid species from biological extracts. The major advantages of ESI-MS are high accuracy, sensitivity, reproducibility, and the applicability of the technique to complex solutions without prior derivatization.
An example of the importance of steroid analysis methods is illustrated by recent advances in understanding the Metabolic Syndrome (MS). Although the MS-associated pathologies may vary, the most common are Obesity, Type II Diabetes, Cardiovascular Disease (e.g. Atherosclerosis, Stroke and Hypertension). Several others have been reported as well. Examples are hypertriglyceridemia, altered levels of sex hormones, hypogonadism in men and nephropathy. Several factors such as gender, age, race, lifestyle and diet may contribute to modify its prevalence: men develop cardiovascular diseases at an earlier age than pre-menopausal women, who seem to be protected by the antioxidant properties of estrogens. Sex steroid hormones play an important role in the appearance and development of the MS and of cardiovascular diseases. Variations in the levels of sex hormones, whether normal or pathological, may have significant influence in the onset of several diseases, metabolic syndrome components included, as well as in changes of biological function of tissues and organs.
For further information on these assays and our standard experimental set-up, please download the CellMade Mass Spectrometry Assays – Technical Information and General Instructions leaflet.