Free androgen index
The free androgen index or FAI is the molar ratio of total testosterone in nmol / l to sex hormone-binding globulin (SHBG) in nmol / l multiplied by 100; as a dimensionless quantity, it does not itself have a unit.
FAI = total (total) testosterone (nmol / l) × 100 / SHBG (nmol / l).
Testing
Numerous medical laboratories offer appropriate tests. Usually 1 ml of serum is required.
rating
The FAI provides an indication of possible hormonal deficiency symptoms or reactive hormonal excess symptoms, i.e. either too little SHBG or too much testosterone is present. There are no standardized framework values for him, only common value ranges as indicators for disturbances. The values usually range from 30 to 150 and are age-dependent.
The sole determination of the testosterone present in the body does not give a clear statement about the proportion of SHBG bound and thus for the bioavailable fraction . Testosterone is only a small part (1 to 2%) in free form and is otherwise bound to SHBG and other plasma proteins ( albumin ). The extraordinarily high affinity to SHBG provides the basis for evaluation via the FAI.
Blood should be taken in the morning as early as possible (between 7:00 and 10:00) due to the daily fluctuations in which the salary decreases with the course of the day.
Reference values
| gender | Age | Standard value |
|---|---|---|
| Women | regardless of age | <5.5 |
| Men | 21-30 | 36-155 |
| 31-40 | 31-116 | |
| 41-50 | 21-69 | |
| 51-60 | 13-61 | |
| 61-70 | 9-49 | |
| > 70 | 7-45 |
Values below 30 in men indicate significant deficiency symptoms with possible effects such as: fatigue, erectile dysfunction , osteoporosis, etc.
Web links
- Free androgen index field trial by Siemens (PDF; 23 kB)
-
Sex hormone binding globulin (SHBG) (PDF; 214 kB)
- Ly LP, Handelsman DJ: Empirical estimation of free testosterone from testosterone and sex hormone-binding globulin immunoassays . In: Eur. J. Endocrinol. . 152, No. 3, March 2005, pp. 471-8. doi : 10.1530 / eje.1.01844 . PMID 15757865 . English
- Leo Vankrieken: Testosterone and the Free Androgen Index (PDF; 39 kB) Diagnostic Products Corporation, Siemens Healthcare. May 1997. Accessed November 1, 2009. English
- Online calculation of the FAI
Individual evidence
- ↑ Polycystic Ovarian Syndrome - Women with androgen excess . Pharmaceutical Newspaper Online. Retrieved November 4, 2015.