Access SHBG Sex Hormone-Binding Globulin 100 determinations, 2 packs, 50 tests/pack

The Access SHBG assay is a paramagnetic particle, chemiluminescent immunoassay for the quantitative determination of Sex Hormone Binding Globulin levels in human serum and plasma using the Access Immunoassay Systems.

INDICATIONS FOR USE
The Access SHBG assay is indicated for use in the assessment of androgen disorders.

SUMMARY AND EXPLANATION
Sex hormone-binding globulin (SHBG) is a glycoprotein responsible for blood transport of testosterone and estradiol.
SHBG is synthesized in the liver and has a high binding affinity for 17-hydroxysteroid hormones. 1,2 Less than 2% of biologically active steroids are free in the circulation with the remainder being bound mostly to SHBG and albumin.
SHBG has a high binding affinity to the 17-hydroxysteroid hormones while albumin has a low binding affinity. 3 Initially, the free portion or unbound hormone fraction was believed to be the only biologically active form. It is now recognized that the portion of hormone that is weakly bound to albumin is also available to the tissues.
The free hormone plus the albumin bound portion of hormones represents the “bioavailable” hormone. 4

The measurement of SHBG can be an important indicator of a chronic or excessive androgenic activity where clinical symptoms would seem to indicate androgen in excess, but androgen levels are normal. Elevated SHBG levels can be seen in persons with androgen insensitivities, hyperthyroidism, cirrhosis of the liver and is found in patients on oral contraceptives or antiepileptic drugs. 4,5,6

Decreased concentrations of SHBG are often seen in men with hypothyroidism and androgen replacement therapy; where women with hirsutism, virilism, polycystic ovarian syndrome (PCOS), elevated androgen levels, obesity and acromegaly will also see a decrease in SHBG levels. 4,7,8 SHBG production is regulated by the androgen/estrogen balance, thyroid hormones, insulin, and dietary factors. 4 The concentration of SHBG is increased by estrogens and decreased by androgens. Therefore, SHBG production is stimulated by estradiol and suppressed by testosterone. As a result, SHBG concentrations are higher in women versus men. 9

Pregnant women have markedly higher SHBG serum concentrations due to their increased estrogen production. 8 Free testosterone can be measured directly by equilibrium dialysis. Alternatively, the non-SHBG-bound fraction may be obtained by precipitation of SHBG-bound testosterone with ammonium sulfate. As both methods are not routinely performed in most laboratories, an indirect method calculation can be utilized to estimate free testosterone. Calculating the Free Testosterone Index (FTI) or the Free Androgen Index (FAI) requires the measurement of total testosterone and SHBG concentrations. 10 The FAI is calculated using the equation