Premenstrual Dysphoric Disorder (PMDD) is characterized by severe and significant mood swings in the days preceding your period. Whilst the exact causal mechanism remains unknown, research suggests that the condition arises from abnormal neurological reactions to hormonal fluctuations occurring during the menstrual cycle.

Attention-deficit/hyperactivity disorder (ADHD) and its symptoms are known to impact men and women differently. Emerging research indicates that the hormonal fluctuations during certain phases of the menstrual cycle, can either worsen, or improve symptom severity in women.

Addiction disorders and addictive behaviors in women have been linked to the menstrual cycle, with substance abuse increasing before and during menstruation for some women. Interesting research is emerging correlating relapse risk with ovulation.

Irritable Bowel Syndrome (IBS) is a common condition that can affect both men and women. However, growing research identifies differences between the sexes in both presentation and symptomatology. For women, the luteal phase of our cycle was correlated with higher constipation frequency and pain severity, likely linked to estrogen and progesterone levels.

Polycystic Ovarian Syndrome (PCOS) affects 5-10% of American women, however research into what causes the disease is still emerging. Several studies have suggested a bi-directional link between gut microbiota and PCOS, endometriosis, and cancer. The microbiome affects every stage and level of female reproduction. Alterations, specifically in the gut microbiome, have specific impacts on the reproductive endocrine system.

Sleep duration and quality can be affected by your menstrual cycle. Elevated progesterone levels in your luteal phase can inhibit the neurotransmitters that regulate your sleep cycle.

REM (rapid eye movement) sleep is a particular type of sleep characterized by intense dreaming. It is important for cognitive development and mood regulation. Elevated progesterone in your luteal phase can also increase body temperature, which can reduce REM sleep during this part of your cycle.

Basal metabolic rate (BMR) may be higher during the luteal phase. This is because an increase in progesterone increases energy use, which can speed up your metabolism.

Insulin resistance is a metabolic syndrome that causes the body’s cells to resist insulin, creating an ineffective uptake of glucose (sugar) from the blood. Chronic high blood sugar is a leading cause of type 2 diabetes. Estrogen has been identified as a protective factor against metabolic syndromes such as insulin resistance. For women, this means our risk of developing insulin resistance and/or diabetes actually increases post menopause, when our estrogen levels decrease. Conversely, progesterone is associated with increased insulin resistance. For women who are premenopausal and already struggling with insulin resistance, blood sugar levels may spike in the mid-luteal phase, due to rising progesterone levels.

Anterior Cruciate Ligament (ACL) tears are more common in women than they are in men. Research has found that the laxity (stiffness) of connective tissues like tendons and ligaments is influenced by estrogen - high estrogen levels can decrease ligament stiffness, making them more prone to tearing. During ovulation, estrogen is at its highest, and women have been found to be at a greater risk of tearing their ACL during this phase of their cycle.

Isometric strength is the force that a muscle or muscular group can produce without significant change in muscle length. In simple terms, it is how long you can hold a wall sit or plank. Isokinetic strength is the peak force a muscle can produce at a constant speed - think running at a fixed speed on a treadmill, or cycling at the same speed on an exercise bike. Research on how fluctuating hormones impact athletic capacity for women has been limited, due to a history of performing sports science studies predominantly on male athletes. Emerging evidence however, is provoking - maximal isometric and isokinetic strength possibly peaks just before and during ovulation. These fluctuations appear to mirror changing estrogen and progesterone levels, with research finding that estrogen has a positive impact on muscle mass and strength.

Subjective athletic performance (i.e. how we feel while exercise) appears to suffer when we are on our period, or in our late luteal phase.

Inflammation is the body’s immune system’s response to injury or infection. Menstruation - the shedding of our uterine lining - is an inflammatory process. Research is emerging that suggests menstrual induced inflammation temporarily impacts the whole body - not just the uterus. Blood draws completed while women were menstruating revealed inflammatory markers that were indicative of systemic - rather than local - inflammation. For women who already deal with chronic inflammation, or reproductive conditions that have an inflammatory component like endometriosis, having a better understanding of how the menstrual cycle can worsen inflammatory symptoms can inform our treatment plans.

Immune response also fluctuates with the menstrual cycle. Immune protection, particularly around the female reproductive tract, weakens during and after ovulation, to increase a woman’s chance of getting pregnant. This ‘dip’ in immunity can increase a woman’s susceptibility to vaginal infections such as thrush, or STD’s like HIV and HPV.

Vasodilation is the widening of blood vessels - it helps maintain healthy blood pressure levels and ensures efficient blood flow. Estrogen has been found to profoundly impact heart health - specifically in its ability to promote vasodilation. During the follicular and ovulatory phase of the menstrual cycle, these cardio-protective benefits may be more pronounced, due to rising estrogen levels.

Heart rate variability (HRV) is a measure of the time variation between heart beats. During the follicular and ovulation phase when estrogen rises and peaks, HRV tends to be elevated. During the luteal phase, when progesterone rises, HRV may decrease. Reduced HRV has been associated with a greater risk for cardiovascular events. For women who are at risk of a cardiovascular event, extra precautions may need to be taken in correlation with their menstrual cycle.

Heavy menstrual bleeding (HMB) and irregular cycles have been associated with cardiovascular disease (CVD). Short cycle length has been associated with an increased risk of coronary heart disease and myocardial infarction (heart attack).

Menopause (the cessation of our periods) is characterized by falling estrogen levels. Given estrogen’s cardioprotective properties, it is unsurprising that CVD risk for women sharply increases post-menopause.