Oral contraceptives and menstrual cycle influence autonomic reflex function

Area of Science:

• Cardiovascular Physiology
• Respiratory Physiology
• Endocrinology

Background:

• Progesterone and its analogues are known to influence ventilation.
• Female sex hormones play a role in regulating physiological responses.
• Understanding hormonal effects on cardiorespiratory control is crucial.

Purpose of the Study:

• To investigate the role of endogenous and pharmaceutical female sex hormones in ventilatory control.
• To examine hormonal influences on the metaboreflex, mechanoreflex, and CO2 chemoreflex.
• To compare ventilatory and hemodynamic responses between oral contraceptive users and non-users.

Main Methods:

• Recruited women aged 18-30, divided into oral contraceptive (OC) users and non-users (NOC).
• Tested participants in low hormone (LH) and high hormone (HH) phases.
• Utilized passive leg movement (PLM), post-exercise circulatory occlusion (PECO), and 5% CO2 breathing challenges.

Main Results:

• Oral contraceptive users showed attenuated pressor responses during PLM and PECO.
• Oral contraceptive users exhibited a greater ventilatory response during PECO.
• Women in the high hormone phase demonstrated an enhanced ventilatory response to 5% CO2 breathing.

Conclusions:

• Oral contraceptive use attenuates pressor responses to metaboreflex and mechanoreflex activation.
• Oral contraceptive use increases ventilatory response to metaboreflex activation.
• Higher hormone phases enhance the CO2 chemoreflex, potentially due to increased progesterone.