Higher cortisol:cortisone ratios in the preovulatory follicle of completely unstimulated IVF cycles indicate oocytes with increased pregnancy potential.

Background: Conception following gonadotrophin-stimulated IVF and embryo transfer has been associated with a higher intrafollicular cortisol:cortisone ratio and decreased metabolism of cortisol to cortisone. The role of glucocorticoids in human oocyte maturation is not fully understood, but active glucocorticoid (cortisol) may be important. This study relates intrafollicular cortisol and cortisone concentrations to oocyte fertilization and embryo implantation in unstimulated cycles.
Methods: Patients aged <40 years with favourable sperm underwent unstimulated IVF-embryo transfer. Study 1 related intrafollicular cortisol levels to oocyte and IVF outcome: (i) fertilized, pregnant (n = 9); (ii) fertilized, not pregnant (n = 21); and (iii) unfertilized (n = 12). Study 2 was a case-control study of 27 patients (same outcome groups of equal size) which measured intrafollicular cortisol, cortisone and the cortisol:cortisone ratio.
Results: Conception cycles demonstrated higher cortisol concentrations compared with the fertilized group (study 1) [median (95% confidence interval): 299 (249-330) versus 227 nmol/l (185-261); P < 0.05] and higher cortisol:cortisone ratios when compared with the unfertilized group (study 2) [7.38 (5.23-9.19) versus 3.56 (1.75-7.46) respectively; P = 0.02]. Of the women with cortisol:cortisone ratios greater than the outcome independent mean of 5.90, 58% conceived compared with only 13% with ratios <5.90 (P < 0.02).
Conclusion: Higher cortisol:cortisone ratios in conception cycles suggest that active glucocorticoid may be important for final oocyte maturation and embryo implantation in unstimulated cycles.