Testosterone (17β-hydroxyandrost-4-en-3-one) is a 19-carbon natural steroid hormone with potent androgenic properties. It maintains testicular function and stimulates the development and maintenance of male characteristics. The majority of methods available to estimate testosterone excretion are based on high- performance liquid chromatography (HPLC), gas chromatography coupled with mass spectrometric (GC-MS), and liquid chromatography coupled with mass spectrometric (LC-MS). The legally demanded detection limit in bovine plasma for HPLC-SP and GC-MS is < 0.1 μg/kg (ppb). For screening purposes the sensitive and cost effective ELISA kits can be used.

Methyltestosterone (17α-methyltestosterone) is a synthetic androgen, differing from testosterone by the presence of a methyl group at the C-17 position. It is one of the anabolic steroids illegally used as a growth promoter in cattle. Methyltestosterone is also commonly used by fish farmers for sex reversal in fish to obtain fast-growing-all-male populations for economic gains. The most popular techniques used for Methyltestosterone detection are physicochemical methods like HPLC and GC/MS. ELISA is also a rapid and cost-effective screening method to control abuse of methyltestosterone by governmental agencies and laboratories.

19-Nortestosterone (17-hydroxyestr-4-en-3-one, 17-19- nortestosterone, also named nandrolone) is a C18 anabolic steroid hormone, which differs from testosterone in that it does not possess a C-19 methyl group [8]. 19-Nortestosterone has been used as a growth promoting agent to accelerate weight gain and improve feeding efficiency in animals. The most popular techniques used for 19-Nortestosterone detection are GC/MS, LC/MS. Competitive EIA methods for determination of nortestosterone have been developed.

Trenbolone is a synthetic analogue of the natural sex hormone testosterone and is used as a growth promoter in meat production. Trenbolone exhibits similar hormonal activity as testosterone but with greater anabolic activity. The use of this compound to increase muscle growth and appetite in cattle breeding is prohibited in the EU since 1988 according to council directive 96/23/EC. For high throughput screening of samples, the ELISA test system is an excellent test which can be used in a variety of matrices.