Menstrual cycle, cortisol awakening response and autonomic nervous system activity

Aim: The relationship between phasical behavioral fluctuations during menstrual cycle and activity of hypothalamo-pituritary-adrenal (HPA) axis or autonomous nervous system (ANS) is not known. Aim of the current study was to assess activity of these two axes by non-invasive means and, for that purpose, to investigate cortisol awakening response (CAR) and diurnal cortisol release and heart rate variability (HRV). Material and Method: In healthy individual, CAR was assessed at 0, 15, 30 and 60 min post-awakening while diurnal cortisol secretion was assessed at 09:00, 12:00, 17:00 and 22:00 hours in the saliva samples. HRV was determined in 5-min electrocardiogram results by assessing the changes in R-R intervals. Cyclic fluctuations in progesterone and estradiol hormones were measured in the saliva. Four study were done to measure: (1) CAR in menstrual, periovulatory, luteal and premenstrual phases (n=68); (2) diurnal cortisol in menstrual, luteal and premenstrual phases (n=16); (3) daily changes in CAR throughout the cycle (n=16); (4) CAR in premenopausal women during menstrual and premenstrual phases (n=15). HRV was assessed in experiments 1 and 3 during menstrual and premenstrual phases. Results: During menstrual phase, CAR was lower (p<0.05) but diurnal cortisol was higher (p<0.02). In the experiment where CAR was assessed daily, there were phasic and daily differences in CAR (p<0.05). In premenopausal women, CAR was lower during menstrual phase (p<0.00). Sympathetic activity was higher during premenstrual period (p<0.05). Conclusion: It has been shown for the first time that daily and phasic changes occur in CAR and that menstrual CAR is lower. Additionally, it has been shown that autonomous activity shows phasical fluctuations. There seems to practical medical implications of both findings.