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Sex-Hormone Binding Globulin (SHBG)

SHGB is the transport protein of testosterone and estradiol in the serum, the tight binding of the hormone to the transport protein prevents the biological activity. SHBG is produced in the liver and in the genitals. The concentration of SHBG depends on several factors:

SHBG lowering factors: androgens, hypothyroidism, obesity, steroid therapy.
SHBG raising factors: age, estrogen, testosterone deficiency, hyperthyroidism, alcoholism, liver disease or several drugs.

Standard Value:

Depending on age and laboratory 15–60 nmol/l.

Laboratory test method:

Sandwich ELISA.

Indications:

SHBG helps to further assess testosterone deficiency in near-normal low testosterone concentrations. The concentration of SHBG enables the calculation of free testosterone with the concentration of testosterone and albumin (Vermeuten et al., 1999) or the calculation of the free androgen index (FAI).

Free testosterone:

1–3% of testosterone in blood is present unbound, more than 97% is bound to binding proteins such as SHBG and albumin. According to Vermeulen's formula, the concentration of testosterone, SHBG and albumin can be used to calculate free testosterone, and the normal value is above 0.25 nmol/l. Free testosterone is considered more clinically relevant than the FAI (Vermeulen et al., 1999).

Free androgen index (FAI):

After the measurement of SHBG and total testosterone, a statement about the bioactive testosterone can be made with the following formula:

FAI = ( Testosterone (nmol/l) × 100 ) \ SHBG (nmol/l)

The standard value of FAI for men is between 30 and 150 depending on age and laboratory. Values below 30 indicate hypogonadism. The free androgen index is considered less reliable than the calculated free testosterone.

Testosterone in serum

Index

FSH in serum

Index: 1–9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

References

Köhn, F.-M. (2004). [diagnosis and therapy of hypogonadism in adult males].
Urologe A, 43(12):1563-81; quiz 1582–3.

Trottmann, M., Dickmann, M., Stief, C. G., and Becker, A. J. (2010). [laboratory workup of testosterone].
Urologe A, 49(1):11-15.

Vermeulen, A.; Verdonck, L. & Kaufman, J. M. A critical evaluation of simple methods for the estimation of free testosterone in serum.
The Journal of clinical endocrinology and metabolism, 1999, 84, 3666-3672

Deutsche Version: Sexualhormon-bindendes Globulin (SHBG)