How Estrogen and Serotonin Affect Mood Swings Before a Woman’s Period

Author: Rohan Smith | Functional Medicine Practitioner | Adelaide, South Australia

Quick Answer

Mood swings before a woman’s period are commonly linked to fluctuations in estrogen and their downstream effects on serotonin, a key neurotransmitter involved in mood regulation. As estrogen rises and falls across the menstrual cycle, it can influence serotonin production, receptor sensitivity, and breakdown. These shifts may contribute to premenstrual symptoms such as irritability, low mood, anxiety, and emotional sensitivity (1–3).

Understanding Estrogen and Serotonin

Serotonin is a neurotransmitter that plays a central role in regulating mood, emotional stability, anxiety, sleep, and appetite. While it is often described as a “feel-good hormone,” serotonin primarily functions as a chemical messenger within the nervous system and is closely linked to hormonal mood changes (4).

Estrogen is a steroid hormone best known for its role in reproductive health, but it also has wide-ranging effects on brain function, neurotransmitter activity, and emotional processing (5).

How Estrogen Influences Serotonin Function

Serotonin Synthesis

Estrogen has been shown to upregulate the activity of tryptophan hydroxylase, the rate-limiting enzyme involved in serotonin synthesis. Higher estrogen availability is associated with increased serotonin production within the brain, a process that may also be influenced by serotonin synthesis and methylation pathways (6,7).

Serotonin Receptor Sensitivity

Estrogen can enhance the expression and sensitivity of specific serotonin receptors, particularly 5-HT_1A and 5-HT_2A receptors. Increased receptor sensitivity allows serotonergic signalling to function more effectively and is associated with greater mood stability (8,9).

Serotonin Reuptake and Availability

The serotonin transporter (SERT) is responsible for clearing serotonin from the synaptic space. Estrogen has been shown to reduce SERT expression and activity, allowing serotonin to remain active for longer periods and potentially enhancing its mood-regulating effects (10,11).

The Menstrual Cycle and Premenstrual Mood Changes

Follicular Phase: Rising Estrogen

During the follicular phase of the menstrual cycle, estrogen levels gradually rise. This increase is associated with enhanced serotonin production and signalling, which often corresponds with improved mood, motivation, and emotional resilience (12).

Luteal Phase: Estrogen Withdrawal

In the luteal phase, particularly in the days leading up to menstruation, estrogen levels decline. This withdrawal can result in reduced serotonin activity, increasing vulnerability to mood symptoms such as irritability, sadness, anxiety, and emotional reactivity. These changes are commonly observed in premenstrual syndrome (PMS) and tend to be more pronounced in premenstrual dysphoric disorder (PMDD) (13,14).

Cognitive Function and Neuroprotection

Estrogen–serotonin interactions are not limited to mood regulation. Together, these systems play an important role in cognitive processes such as memory, learning, and emotional regulation. Estrogen supports synaptic plasticity and neuroprotection, in part through its influence on serotonergic pathways (15,16).

Menopause and Mood Vulnerability

During the menopausal transition, sustained declines in estrogen can disrupt serotonergic signalling. This neurochemical shift may contribute to the increased risk of depressive symptoms, anxiety, and mood instability reported by some women during perimenopause and menopause (17,18).

Why This Matters Clinically

Understanding how estrogen modulates serotonin helps explain why mood symptoms often follow predictable hormonal patterns across the menstrual cycle. It also provides insight into why broader hormonal imbalances may further influence mood regulation and emotional wellbeing. This understanding also helps explain why certain interventions—such as selective serotonin reuptake inhibitors (SSRIs) or hormone-based therapies—may reduce premenstrual mood symptoms in some individuals (19,20).

When to Consider Further Support

Premenstrual mood changes that are severe, persistent, or disruptive to daily functioning may warrant further assessment. This includes symptoms suggestive of PMDD, mood changes that worsen predictably across the cycle, or emotional symptoms occurring alongside fatigue, sleep disruption, or hormonal irregularities.

Key Takeaways

• Estrogen plays a regulatory role in serotonin production, receptor sensitivity, and reuptake.
• Declining estrogen levels in the luteal phase may reduce serotonin activity.
• These neurochemical changes help explain common premenstrual mood symptoms.
• Hormonal mood shifts reflect physiological processes, not personal weakness.

Understanding Hormonal Mood Shifts — and Knowing When to Look Deeper

Premenstrual mood changes can be distressing, especially when they recur predictably each month or begin to affect relationships, work, or overall wellbeing. Because estrogen and serotonin are closely linked, mood symptoms often reflect underlying hormonal patterns rather than isolated emotional concerns.

At Elemental Health and Nutrition, individuals in Adelaide are supported through an evidence-informed functional medicine approach that considers hormonal rhythms, nervous system regulation, nutritional status, and lifestyle factors together. A personalised assessment may help clarify contributing physiological drivers and guide appropriate next steps for long-term mood and hormonal support.

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