• Highly specific monoclonal antibody to ensure accuracy of reported result
  • Highly reproducible results
  • Suitable for measurement of a variety of sample types
  • All reagents are ready to use
  • Part of a developing panel of steroid hormone assays

An automated assay for the quantitative determination of free testosterone in human serum or plasma. Measurements of testosterone are used in the diagnosis of disorders involving the male sex hormones (androgens).

Testosterone (17β-OH-4-androstene-3-one) has a molecular weight of 288 Daltons and is considered to be the principle androgen found in circulation of mature male mammals1. In males it is synthesised and secreted by the Leydig cells located in the interstitium of the testis, and in females testosterone is produced in various locations such as the ovaries, adrenal gland and peripheral tissues, with additional production due to inter-conversion from other steroid hormones. The secretion of testosterone is regulated by luteinising hormone (LH). Testosterone is found in circulation predominantly linked to carrier proteins, the most common of which being sex-hormone binding globulin (SHBG).

Testosterone plays a key part in the development of reproductive tissues and secondary sex characteristics in men. There is an observed and well documented circadian variation of testosterone levels in men with the circulating concentration being higher in the morning and declining throughout the day2. Testosterone levels also decline in ageing males (andropause) and is often associated with loss of muscle and bone mass, leading to osteoporosis, loss of libido, erectile dysfunction, depression and impaired cognitive function3.

In males, the major causes of suppressed testosterone levels include Klinefelter’s Syndrome, testicular damage and pituitary disorders.

In females of all ages, elevated testosterone levels can be associated with a variety of virilising conditions including adrenal tumours and polycystic ovarian syndrome (PCOS).

Measurement of free testosterone can be considered useful in the diagnosis of several conditions including androgen deficiency in men and androgen excess in women4. Assessment of free testosterone levels may prove beneficial5 and may avoid an incorrect diagnosis of hypogonadism in cases when low concentrations of total testosterone are determined and alterations of SHBG are suspected.

1. Jamerson. JL, de Kretser. D, Marshall. JC and De Groot. LJ. Endocrinology – adult and pediatric 6th edition. pp 368-374

2. Brambilla. DJ, Matsumoto. AM, Araujo. AB, McKinlay. JB. The Effect of Diurnal Variation on Clinical Measurement of SerumTestosterone and Other Sex Hormone Levels in Men. J Clin Endocrinol Metab. 2009 Mar; 94(3): 907–913

3. Rajfer, J. Decreased Testosterone in the Aging Male. Rev Urol. 2003;5(suppl 1):S1–S2

4. Shea JL, Wong PY, Chen Y. Free testosterone: clinical utility and important analytical aspects of measurement. Adv Clin Chem. 2014;63:59-84

5. Diver MJ. Analytical and physiological factors affecting the interpretation of serum testosterone concentration in men. Ann Clin Biochem. 2006 Jan;43(Pt 1):3-12.