Testosterone, Free
High Quality Assays with Reproducible and Reliable Results
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The DRG:HYBRiD-XL Free Testosterone is an enzyme immunoassay for the quantitative in vitro diagnostic measurement of free testosterone in serum and plasma.Only for use with the DRG:HYBRiD-XL Analyzer.Testosterone is a steroid hormone (androgen) produced by special endocrine tissue (the Leydig cells) in the male testicles. It is also produced by the adrenal glands in both males and females and, in small amounts, by the ovaries in females. Testosterone effects can be classified as virilizing and anabolic effects. Virilizing effects include maturation of the sex organs. Anabolic effects include growth of muscle mass and strength, increased bone density and strength, and stimulation of linear growth and bone maturation. It is presentin large amounts in males during puberty and in adult males. In women, testosterone is converted to estradiol, the main sex hormone in females. Testosterone production is stimulated and controlled by luteinizing hormone (LH), which is manufactured by the pituitary gland. Testosterone levels are diurnal, peaking in the early morning hours and with the lowest levels in the evening. Levels also increase after exercise and decrease with age. Testosterone is present in the blood as "free" testosterone (1-4%) or bound testosterone (~98%). The latter may be loosely bound to albumin (38%), or to a specific binding protein called Sex Hormone Binding Globulin (SHBG) (60%). Both the albumin-bound and free fractions may be biologically active, while SHBG effectively inhibits testosterone action. Measurement of the free or unbound fraction of serum testosterone has been proposed as a means of estimating an abnormal testosterone level in males and females. Free testosterone levels are elevated in women with hyperandrogenism associated with hirsutism in the presence or absence of polycystic ovarian disease. It may also help diagnose premature or delayed puberty in females and infertility in males. In addition, free testosteronemeasurements may be more useful than total testosterone in situations where SHBG is increased or decreased. Decreased SHBG levels can be seen in obesity, hypothyroidism, androgen use, and nephritic syndrome. Increased levels are seen in cirrhosis, hyperthyroidism, and estrogen use.The DRG:HYBRiD-XL Free Testosterone Kit is a solid phase enzyme-linked immunosorbent assay (ELISA) based on the principle of competitive binding. The antibody coated wells (ACW) of the reagent cartridges are coated with a monoclonal [mouse] antibody directed towards a unique antigenic site of the testosterone molecule. Endogenous free testosterone of a patient sample competes with a testosterone-horseradish peroxidase conjugate for binding to the coated antibody. After incubation the unbound conjugate is washed off. The amount of bound peroxidase conjugate is inversely proportional to the concentration of free testosterone in the sample. Having added the substrate solution, theintensity of colour developed is inversely proportional to the concentration of free testosterone in the patient sample.
