Testosterone (17ß-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.

May be diagnosed by:

• Determination of specific antibodies based on the ELISA technique
• Determination of specific antibodies based on the RIA-technique

Testosterone ELISA:

Competitive immunoenzymatic colorimetric method for quantitative determination of Testosterone in serum or plasma.

Principle 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  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.

Specific performance characteristics:  

Correlation with RIA performed on 52 samples is r = 0.956

Order information: