Pre Menstrual  Symptoms: What Causes Them and Why They Happen

In the previous article, we explored how Premenstrual Syndrome (PMS) develops and why some women are more sensitive to hormonal fluctuations than others. We learned that PMS is not simply caused by “too many hormones” or “too few hormones.” Instead, it appears to result from the interaction between changing hormone levels, neurotransmitters in the brain, inflammation, stress physiology, and individual sensitivity.

But what exactly causes the symptoms?

Why do some women become bloated before their period? Why do breasts become tender? Why can emotions suddenly feel overwhelming? Why do food cravings appear seemingly out of nowhere?

Let’s take a closer look at the most common PMS symptoms and the biological mechanisms behind them.

Bloating and Water Retention

One of the most common PMS complaints is bloating. Many women feel that their abdomen becomes swollen, their clothes fit more tightly, and they may even gain several pounds before menstruation.

What Causes It?

The main hormonal player is progesterone.

After ovulation, progesterone rises dramatically. Progesterone influences fluid balance through several mechanisms.

First, progesterone interacts with mineralocorticoid receptors involved in sodium and water regulation. This can alter how the kidneys handle fluid and electrolytes.

Second, progesterone affects blood vessel permeability. Small amounts of fluid can more easily move from blood vessels into surrounding tissues.

Third, progesterone relaxes smooth muscles throughout the body, including those in the digestive tract.

As digestion slows, food remains longer in the intestines. This can contribute to:

• abdominal fullness
• gas
• constipation
• feelings of heaviness

For some women, the combination of fluid retention and slower digestion creates significant abdominal bloating during the late luteal phase.

Why Does It Improve When Menstruation Starts?

As progesterone levels rapidly fall before menstruation, fluid regulation gradually returns toward baseline. Excess fluid is often eliminated during the first days of menstruation, explaining why bloating frequently improves once bleeding begins.

Breast Tenderness and Breast Swelling

Many women notice that their breasts feel swollen, heavier, or painful before their period.

This symptom is known as cyclical mastalgia.

What Causes It?

Both estrogen and progesterone contribute.

During the second half of the cycle:

• Estrogen promotes growth and activity within breast tissue.
• Progesterone stimulates changes in milk-producing glands.

At the same time, fluid retention within breast tissue increases.

The combination of tissue expansion and increased fluid content stretches surrounding structures and nerve endings, producing:

• tenderness
• soreness
• heaviness
• swelling

Women with stronger hormonal sensitivity often experience more severe symptoms.

Mood Swings and Emotional Sensitivity

Many women report feeling emotionally vulnerable before menstruation.

Small frustrations may suddenly feel overwhelming. Some women cry more easily, become more sensitive to criticism, or feel emotionally fragile.

What Causes It?

The answer largely involves estrogen and serotonin.

Estrogen supports serotonin production and receptor sensitivity.

Serotonin helps regulate:

• mood
• emotional stability
• stress resilience
• feelings of well-being

During the late luteal phase, estrogen levels fall.

For women sensitive to these hormonal changes, serotonin activity may decrease.

This can lead to:

• emotional sensitivity
• increased reactivity
• sadness
• reduced stress tolerance

The emotional response itself is real. Women are not imagining these changes; measurable neurochemical shifts are occurring within the brain.

Irritability and Anger

Many women describe feeling “short-tempered” before menstruation.

Minor inconveniences that would normally be manageable may suddenly trigger frustration or anger.

What Causes It?

Several factors likely contribute.

Falling estrogen may reduce serotonin activity.

At the same time, changes in progesterone and its metabolite allopregnanolone affect GABA receptors.

GABA is the brain’s primary calming neurotransmitter.

In many women, allopregnanolone promotes relaxation. However, in susceptible individuals, fluctuations in allopregnanolone may paradoxically increase:

• irritability
• tension
• emotional instability

This may explain why some women feel emotionally unsettled during the days preceding menstruation.

Anxiety and Nervous Tension

For some women, PMS is characterized more by anxiety than sadness.

They may experience:

• nervousness
• racing thoughts
• tension
• restlessness
• feelings of being overwhelmed

What Causes It?

Again, progesterone and allopregnanolone play important roles.

The brain normally adapts to changing levels of these hormones throughout the cycle.

However, some women appear particularly sensitive to luteal-phase fluctuations.

As progesterone declines before menstruation, changes in GABA signaling may temporarily increase anxiety symptoms.

Stress can significantly amplify this effect.

Women under chronic stress often report more severe PMS-related anxiety because elevated cortisol further disrupts neurotransmitter balance.

Fatigue and Low Energy

Many women feel exhausted during the days leading up to menstruation.

Why Does This Happen?

Several factors may contribute simultaneously.

Increased Progesterone

Progesterone naturally has calming and sedative properties.

For some women, high progesterone levels create:

• sleepiness
• reduced motivation
• lower energy levels

Changes in Neurotransmitters

Fluctuations in serotonin can affect motivation and energy production.

Increased Energy Requirements

The luteal phase is metabolically active.

Research suggests that energy expenditure may increase slightly after ovulation.

The body is maintaining the uterine lining and preparing for a possible pregnancy.

This increased physiological demand may contribute to feelings of fatigue.

Sleep Disturbances

Many women sleep less well before menstruation, which further worsens fatigue.

Food Cravings

Cravings for chocolate, sweets, salty foods, or carbohydrates are among the most recognizable PMS symptoms.

Why Do Cravings Occur?

Several mechanisms are involved.

Serotonin

Low serotonin activity can increase cravings for carbohydrate-rich foods.

Carbohydrates temporarily increase serotonin availability in the brain, creating short-term improvements in mood.

The brain may therefore drive cravings as an attempt to compensate for changing neurotransmitter levels.

Blood Sugar Regulation

Hormonal fluctuations may influence insulin sensitivity.

Some women become more vulnerable to blood sugar fluctuations during the luteal phase, increasing hunger and cravings.

Increased Energy Needs

The body may naturally require slightly more calories during the luteal phase.

Some studies suggest that calorie requirements increase by approximately 100–300 calories per day after ovulation.

Headaches and Migraines

Hormonal headaches frequently occur before menstruation.

Why?

The primary trigger appears to be estrogen withdrawal.

When estrogen falls rapidly before menstruation, susceptible women may develop:

• headaches
• migraines
• increased sensitivity to light
• nausea

Estrogen influences blood vessel tone, neurotransmitter activity, and pain perception.

Rapid hormonal changes can therefore trigger migraine pathways in vulnerable individuals.

Acne and Skin Changes

Many women experience breakouts before their period.

What Causes It?

Although estrogen declines before menstruation, androgen activity becomes relatively more dominant.

Androgens stimulate sebaceous glands within the skin.

This increases:

• oil production
• clogged pores
• inflammation

The result may be:

• acne
• pimples
• oily skin

Most commonly around:

• the chin
• jawline
• lower face

Sleep Disturbances

Some women struggle with sleep during the late luteal phase.

Why?

Several mechanisms may contribute:

• anxiety
• elevated stress levels
• temperature regulation changes
• fluctuating progesterone levels

Progesterone raises basal body temperature after ovulation.

This slight increase may make some women more susceptible to nighttime awakenings.

Poor sleep further worsens mood symptoms, cravings, and fatigue.

Brain Fog and Difficulty Concentrating

Many women report feeling mentally slower before menstruation.

They may experience:

• forgetfulness
• difficulty concentrating
• reduced productivity
• mental fatigue

Why Does This Happen?

The exact mechanism remains under investigation.

However, hormonal fluctuations influence:

• serotonin
• dopamine
• GABA
• stress hormone signaling

These systems all contribute to attention, motivation, and cognitive performance.

For some women, the late luteal phase may temporarily reduce mental sharpness.

Constipation Before Menstruation

Progesterone slows smooth muscle activity throughout the body.

This includes the muscles responsible for moving food through the intestines.

As a result:

• bowel movements slow down
• stool remains longer in the colon
• more water is absorbed
• constipation becomes more likely

This effect is strongest during the progesterone-dominant luteal phase.

Diarrhea When Menstruation Begins

Ironically, constipation may suddenly switch to diarrhea once menstruation starts.

Why?

The main culprit is prostaglandins.

As menstruation begins, the uterus produces prostaglandins to help shed the uterine lining.

These compounds stimulate uterine contractions.

Unfortunately, they also affect nearby intestinal muscles.

The result can be:

• loose stools
• diarrhea
• abdominal cramping
• more frequent bowel movements

Women with severe menstrual cramps often experience more severe digestive symptoms because both are driven by higher prostaglandin activity.

Changes in Libido

Sexual desire may fluctuate throughout the cycle.

Many women experience peak libido near ovulation when:

• estrogen is high
• testosterone is relatively higher
• fertility is greatest

By contrast, libido may decrease during the late luteal phase.

Why?

Several factors contribute:

• declining estrogen
• increasing fatigue
• bloating
• breast tenderness
• mood symptoms

Some women, however, experience increased desire shortly before menstruation, highlighting the highly individual nature of hormonal responses.

Key Takeaways

PMS symptoms arise from a complex interaction between reproductive hormones, neurotransmitters, prostaglandins, fluid regulation, inflammation, and stress physiology.

The symptoms are real biological responses to hormonal fluctuations. Estrogen, progesterone, serotonin, GABA, cortisol, and prostaglandins all contribute to the emotional, physical, and cognitive changes many women experience during the days leading up to menstruation.

Understanding the mechanisms behind these symptoms can help women recognize that PMS is not a sign of weakness or poor self-control. It is a physiological process that varies greatly between individuals. While some women experience only mild changes, others may face significant challenges that deserve understanding, support, and appropriate care.

In the next article, we will explore what can make PMS worse, including stress, poor sleep, dietary factors, inflammation, and hormonal imbalances, and discuss evidence-based strategies that may help reduce symptoms naturally.