Validity of Serum Testosterone, Free Androgen Index, and Calculated Free Testosterone in Women with Suspected Hyperandrogenism

Objectives: There are technical limitations for the currently available methods of measuring serum total and free testosterone in females. The study objectives were to evaluate the usefulness of serum total testosterone, sex hormone-binding globulin (SHBG), free androgen index (FAI), and calculated free testosterone (CFT) in the assessment of androgen status in women investigated for suspected hyperandrogenism.

Methods: This is a case control study that was conducted during the period from 1(st) May 2011 to 31(st) October 2011 on 122 patients aged (18-45 years) whom were referred to the Clinical Biochemistry Laboratory from the Endocrinology and Gynecology Clinics, Royal Hospital, Oman. Women with no clinical feature or laboratory data indicative of hormonal dysfunction and with midluteal progesterone >30 nmol/L were selected as controls (group 1; n=18). The patients were divided into subgroups based on the clinical/laboratory diagnosis of polycystic ovary syndrome (PCOS [group 2; n=19), hirsutism (group 3; n=18), menstrual disturbances (irregularities) or infertility (group 4; n=49), as well as combination of PCOS or hirsutism and menstrual disturbances or infertility (group 5; n=18). Serum total testosterone and SHBG were measured, FAI was calculated as percentage ratio of total testosterone to SHBG values, and CFT was calculated according to Vermeulen equation.

Results: There was a statistically significant difference in the mean levels of testosterone, FAI and CFT in each patient group compared with the control group. For diagnosing hyperandrogenism, each indicator was selected at the recommended cut-off: testosterone >3.0 nmol/L, SHBG <30 nmol/L, FAI >5%, and CFT >32 pmol/L. In group 2, 89.5% and 94.7% of the patients had increased FAI and CFT, respectively; compared with 36.4% for increased testosterone. In group 3, 88.9% and 88.9% of the patients had similarly increased FAI and CFT, respectively; compared with 66.7% for testosterone. In group 4, patients had 63.3% and 73.5% elevated FAI and CFT, respectively; compared with 53.1% for testosterone, while in group 5, patients had 83.3% and 88.9% elevated FAI and CFT, respectively, compared with 61.1% for testosterone.

Conclusion: The diagnosis of hyperandrogenism was most obvious when using CFT or FAI than testosterone alone. It is thus recommended to include these calculated parameters (CFT and/or FAI) in the routine investigation and assessment of women with disorders related to clinical or biochemical hyperandrogenism.