Stress-induced increases in progesterone and cortisol in naturally cycling women

• Progesterone rises in response to stress during the follicular phase.
• Baseline progesterone was associated with greater cortisol response to stress.
• Cortisol response to stress mediated progesterone responses to stress.

Studies with animals of both sexes show that the adrenal glands release progesterone in addition to cortisol in response to stress. However, little is known about the progesterone response to stress in naturally cycling women. We investigated the effect of stress on estradiol, progesterone, and cortisol levels in women during the follicular phase of the menstrual cycle. We found that physical stress (the cold pressor test) had no effect on estradiol levels, but increased progesterone and cortisol. We also found positive correlations between baseline progesterone and cortisol levels, as well as between the change in progesterone and cortisol before and after water exposure in both the stress and control sessions. Mediation analyses revealed during the stress session, the change in progesterone from baseline to 42-min post-stress onset was mediated by the magnitude of change in cortisol levels across the same time span. Overall, these findings reveal that progesterone released in response to stress as observed in animals and men extends to women during the low ovarian output follicular phase of the menstrual cycle, and that the mechanism of release may be similar to the mechanism of cortisol release.