The Association of Body Mass Index and Biochemical Hyperandrogenaemia in Women with and Without Polycystic Ovary Syndrome

Objective: To investigate the association between BMI and different androgen parameters in women with PCOS and normal ovulatory women.

Study Design: A cross sectional, observational study was carried out. A total of 286 patients aged 20-44years were recruited. One hundred and sixty-five women had a diagnosis of PCOS and 121 women were ovulatory with no clinical or biochemical or ultrasound evidence of PCOS. The PCOS and non-PCOS groups were sub-divided into two subgroups based on BMI (BMI≤30kg/m(2) and BMI>30kg/m(2)). Androgen parameters measured were testosterone, androstenedione, free androgen index and sex hormone-binding globulin (SHBG). Testosterone and androstenedione were measured using tandem mass spectrometry. Free androgen index (FAI) was calculated using the formula: (testosterone/SHBG)×100. Spearman rank correlations were used to determine relationship between BMI and androgens.

Results: The PCOS group had a higher BMI compared with the non-PCOS group (28.9±5.8, 24.5±4.1). Total testosterone, androstenedione, and FAI were significantly higher while SHBG was lower in the PCOS group. A correlation between BMI and total testosterone was not observed in either group. Positive correlations were observed between BMI and FAI in both PCOS (p<0.001) and non-PCOS groups (p=0.02) while a positive correlation was observed between BMI and androstenedione in the PCOS group (p=0.001). SHBG correlated negatively with BMI in both groups.

Conclusion: A strong correlation exists between BMI and FAI but not with total testosterone, possibly due to the mediation of SHBG. Hyperandrogenaemia in the form of androstenedione seems to be augmented in PCOS with increasing BMI. A direct causal relationship between BMI and androgenaemia was not established.