Testosterone

GWB-BA839A

Testosterone (17& beta; -Hydroxy-4-androstene-3-one) is a steroid hormone from the androgen group. In postpubertal males testosterone is secreted primarily by the testes with only a small amount derived from peripheral conversion of androstenedione. In adult women over 50% of serum testosterone is derived from peripheral conversion of androstenedione secreted by the adrenal and ovary with the remainder from direct secretion of testosterone by these glands. The majority of circulating testosterone is bound by SHBG and a smaller portion is bound by albumin. Only 1-2% exists in circulation as unbound or free testosterone. Testosterone effects can be classified as virilizing and anabolic effects although the distinction is somewhat artificial as many of the effects can be considered both. Anabolic effects include growth of muscle mass and strength increased bone density and strength and stimulation of linear growth and bone maturation. Virilizing effects include maturation of the sex organs and after birth (usually at puberty) a deepening of the voice growth of the beard and axillary hair (male secondary sex characteristics). Testosterone levels decline gradually with age in men (andropause). The signs and symptoms are non-specific and are generally associated with aging such as loss of muscle mass and bone density decreased physical endurance decreased memory ability and loss of libido. In females of all ages elevated testosterone levels can be associated with a variety of virilizing conditions including adrenal tumors and polycystic ovarian disease. Principles of the assay: Microtiter strip wells are precoated with anti-Testosterone antibodies (solid-phase). Testosterone in the sample competes with added horseradish peroxidase labelled Testosterone (enzyme-labelled antigen) for antibody binding. After incubation a bound/free separation is performed by solid-phase washing. The immune complex formed by enzyme-labelled antigen is visualized by adding Tetramethylbenzidine (TMB) substrate which gives a blue reaction product. The intensity of this product is inversely proportional to the amount of Testosterone in the sample. Sulphuric acid is added to stop the reaction. This produces a yellow endpoint colour. Absorption at 450 nm is read using an ELISA microwell plate reader. Storage and Stability: The reagents are stable up to the expiry date stated on the label when stored at 2. . . 8 & deg; C. Limitations of the Test: Bacterial contamination or repeated freeze-thaw cycles of the specimen may affect the absorbance values. References Joshi U. M. et al. ; Steroids 1979 34 (1) 35Turkes A. et al. ; J Endocrinol. 1979 81 (2) P165Ismail A. A. Niswender G. D. Midgley A. R. ; J. Clin. Endocr. Metab. 1972 34 177 ? 184Rajkowski K. M Cittanova N Desfosses B. and Jayle M. F. Steroids 29 no 5 1977Widsdom G. B. ; Clin. Chem. 1976 22/8 1243 - 1255