IIT Madras & US Researchers study impact of Oral Contraceptives on Blood Pressure

CHENNAI : Indian Institute of Technology Madras (IIT Madras) and University of Minnesota, U.S. Researchers are studying the impact that oral contraceptives can have on the blood pressure of women who engage in dynamic exercises.

Certain oral contraceptives are known for increasing resting blood pressure but the exercise blood pressure response during large muscle exercise (like cycling or running) is not currently well-understood. In addition, research was equivocal on whether blood pressure was, indeed, influenced by the hormonal fluctuations during the menstrual cycle.

The research team identified that both oral contraceptive use and general fluctuations in endogenous ovarian hormone (like estrogens) in young women (20-25 years of age), did not influence blood pressure with lower body exercise and activation of skeletal muscle sensory neurons, which are known to contribute to exaggerated blood pressure responses in people with cardiovascular diseases.

The lead investigators of this research included Dr. Manda Keller Ross and Mr. Miguel Anselmo from the University of Minnesota, Minneapolis, U.S. and Dr. Ninitha A.J., Assistant Professor, Department of Biotechnology, IIT Madras. Dr. Ninitha AJ. received support through the Science and Engineering Research Board’s ‘Core Research’ Grant while Prof. Manda Keller Ross was supported by National Institutes of Health (NIH), U.S.

Their findings were published in the reputed peer-reviewed journal American Journal of Physiology – Regulatory, Integrative and Comparative Physiology (https://doi.org/10.1152/ajpregu.00017.2024)

Elaborating on this research, Dr. Ninitha A.J., Assistant Professor, Department of Biotechnology, IIT Madras, said, “Oral contraceptives or birth control pills are taken by women to prevent pregnancy, reduce acne, menstrual cramps, and risk of ovarian cysts. According to a study by Martin and colleagues, around 70 % of female athletes took oral contraceptives at a point in their career and thus it is important to understand how they affect blood pressure. The findings of this study have wide application and are of importance as it sheds light on the influence of oral contraceptives on blood pressure response to exercise in women.”

Further, Dr. Manda Keller Ross, Assistant Professor at the University of Minnesota, Minneapolis, U.S., added, “We have little information on how the EPR changes in women across the life span. Menopause, the cessation of hormone production in the ovaries, occurs at around 50 years old and cardiovascular risk increases in women throughout and after the menopause transition. The next step of this work is to determine if the EPR is a contributing factor to the cardiovascular risk in menopausal females.”

Exercise can acutely increase blood pressure due to increased sympathetic nerve activity (fight or flight) from skeletal muscle sensory neurons known as ‘Exercise Pressor Reflex’ (EPR). The EPR results in an increase in blood flow from the heart to the skeletal muscle to meet the needs of the muscle. The EPR is known to be greater in males compared with premenopausal females and is also known to be exaggerated in people with cardiovascular disease.

Estrogens are cardioprotective, they reduce sympathetic activity and increase blood flow to the skeletal muscle via nitric oxide bioavailability. Thus, the researchers expected that during the ovulation phase of their menstrual cycle, when estadiol peaks, women would have the lowest EPR compared with females during the early follicular phase (where estradiol is the lowest) and with oral contraceptive use, which also results in low serum estradial levels.

However, the researchers demonstrated that regardless of the phase of the menstrual cycle or oral contraceptive use, the EPR was similar in the women. This suggests that oral contraceptives do not increase the blood pressure response in women more so than in those who do not use oral contraceptives.

Sex differences in the cardiovascular response to exercise have been demonstrated and may be dependent on sex hormone levels. Furthermore, oral contraceptives (OCs) have been shown to exaggerate the blood pressure response to upper extremity exercise.

The results of this study indicate that neither endogenous nor exogenous (OC) sex hormones modulate BP during lower extremity dynamic exercise or with group III/IV afferent activation in young, healthy females.