Serotonin (the happiness hormone) – what is it and how does it relate to the other hormonal phases?

If, every time you feel low, sensitive, unmotivated or without any joy in life before your period, you tell yourself it's all in your head – then you should know: that simply isn't true. Serotonin has a decisive influence on your mood, and when its levels drop, as happens during the menstrual phase, that's a real and entirely understandable reason for your lack of enthusiasm and joy.

But what exactly is the connection between serotonin and your menstrual cycle? We explain how each phase of your cycle affects your serotonin levels and what you can do to stay balanced throughout.

What is serotonin? 

Serotonin, also known as the "happiness hormone", is a neurotransmitter that supports communication between the nerve cells in the brain and the rest of the body.

It acts rather like the brain's messenger, relaying signals and impulses through the nervous system and telling the body how to function – which means it plays an important role in a whole host of processes.

Sleep, mood, regulation of anxiety, digestion, wound healing, bone health, blood clotting, libido – serotonin is involved in all of these. At the same time, low serotonin levels have been linked to depression, mania and other health problems.

Serotonin vs dopamine – what's the difference? 

Both serotonin and dopamine are neurotransmitters, that is, chemical messengers that carry impulses and signals from the nerve cells in the brain to the rest of the body. Both are considered happiness hormones and both are involved in regulating mood, which is why they're easily confused. There are, however, crucial differences in their roles and how they work.

Serotonin influences mood, sleep, digestion and other bodily functions. Low serotonin levels in the body can cause sleep disturbances, anxiety and depression.

Dopamine, on the other hand, is primarily associated with pleasure, motivation, satisfaction and reward. Low dopamine levels can lead to exhaustion and a lack of motivation.

What role does serotonin play in the body? 

The emotions you feel, your moods, but also essential bodily functions such as movement and blood clotting are all influenced by serotonin. Its job is to regulate feelings of happiness and anxiety and to ensure the body functions well, both physiologically and psychologically.

The functions of serotonin in the brain and body 

• general details
• we mention that it influences the following:
• sleep
• memory
• bone metabolism
• sexual behaviour
• mood
• appetite
• endocrine system
• blood clotting

Serotonin is more than just a natural mood stabiliser: serotonin levels serve numerous functions in the body and also have a direct effect on sleep, digestion and the ability to heal. It is found throughout the body and influences:

• Sleep: during sleep, serotonin is involved in the alternation between REM and non-REM phases.
• Memory: serotonin influences the duration and intensity of memories, particularly those from a social or emotional context.
• Bone metabolism: very high serotonin levels have been linked to osteoporosis.
• Sexual behaviour: serotonin is involved in controlling sexual function.
• Mood: in the brain, serotonin's task is to balance states such as happiness and anxiety.
• Appetite: serotonin can reduce appetite and heighten the feeling of fullness.
• The endocrine system: serotonin can interact with oestrogen and thyroid hormones and is even involved in the stress response and insulin secretion.
• Blood clotting: high serotonin levels are associated with vasoconstriction of the arteries and the formation of blood clots, which can speed up healing when you're injured.

Why do serotonin levels drop?

As a rule, a healthy serotonin level in the body falls within the range of 80–400 micrograms per litre. There are, however, situations in which this value falls below the optimum – for reasons that may involve a number of biological, psychological or lifestyle factors.

The most common causes of a drop in serotonin include:

• Chronic stress
• Nutrient deficiencies
• Lack of exposure to natural light
• Sleep disorders
• Excessive consumption of alcohol or harmful substances
• Various medical or psychiatric conditions

The connection between serotonin and the female hormones 

Serotonin interacts with the female hormones and contributes to mood as well as to the functioning of the reproductive system. This is precisely why serotonin levels fluctuate markedly alongside oestrogen and progesterone, influencing mood, emotions and bodily functions – particularly across the menstrual cycle, during pregnancy and in the menopause.

Oestrogen and the stimulation of serotonin levels 

Oestrogen can influence the synthesis and metabolism of serotonin, and fluctuations in oestrogen can in turn cause serotonin levels in the brain to rise and fall.

Precisely because the two are so closely linked, their interplay can intensify premenstrual symptoms. Oestrogen levels fall during the luteal phase, which brings about a change in serotonin levels and therefore, automatically, noticeable mood swings.

The link between oestrogen and serotonin is particularly strong during pregnancy, when the high level of oestrogen in the body stimulates a rise in serotonin levels and increases its effectiveness in the brain.

Progesterone and serotonin sensitivity 

Progesterone's effect on serotonin in the brain is the opposite of oestrogen's. It can lower serotonin levels by increasing the activity of the enzymes that break serotonin down.

Progesterone influences both serotonin levels and sensitivity to this neurotransmitter. This happens particularly across the menstrual cycle, when the female hormones undergo natural fluctuations.

Before menstruation, it isn't only the falling oestrogen production that causes serotonin levels to drop, but also the rise in progesterone. These fluctuations can therefore bring about mood changes, anxiety and depressive symptoms – precisely because they alter the amount of serotonin in the brain.

How do a woman's hormonal phases affect serotonin levels?

Since the phases of the menstrual cycle are closely tied to fluctuations in oestrogen and progesterone, and these two female hormones in turn influence the synthesis and metabolism of serotonin, there is a close relationship between the menstrual cycle and serotonin levels in the brain.

Numerous studies have already demonstrated the correlation between oestrogen and serotonin levels during the menstrual cycle. Each phase of the cycle has its own effect and triggers different changes in serotonin within the body.

Various hormonal imbalances can also lead to fluctuations in the amount of serotonin in the body and have a considerable impact on mood, sleep and behaviour.

Follicular phase 

During the follicular phase, when oestrogen is produced in abundance, it stimulates serotonin synthesis and causes levels of this neurotransmitter to rise. These changes contribute to a more positive mood, more energy and a higher pain threshold, as well as improved cognitive performance.

Ovulation 

At ovulation, oestrogen levels in the body reach their peak, immediately followed by a sudden drop. This also causes serotonin to fluctuate and affects mood and motivation.

Luteal phase 

In the luteal phase, both the rise in progesterone and the falling production of oestrogen contribute to a decrease in serotonin levels. When this happens, mood becomes less positive, energy and motivation decline, and symptoms of anxiety or depression may appear.

Menstruation 

Progesterone and oestrogen levels are at their lowest during menstruation, and serotonin levels are usually low during this time too. This is why the symptoms that appeared during the luteal phase in response to falling serotonin levels persist through menstruation as well, until oestrogen levels begin to rise again.

Maintaining optimal serotonin levels according to your cycle phase 

Keeping serotonin levels stable throughout the menstrual cycle – despite the hormonal changes – can be a great help in managing mood swings and symptoms of premenstrual syndrome.

As a rule, changes to lifestyle and diet play an important part in stimulating and maintaining optimal serotonin levels.

Where hormonal imbalances are concerned, however, it's important to speak to a doctor and seek support in order to keep serotonin fluctuations under control.

Recommended foods for maintaining hormonal balance 

In the body, serotonin is synthesised from tryptophan, an essential amino acid used in protein biosynthesis. The fact that it is an essential amino acid means the body cannot produce it itself and must obtain it from outside, through food.

To maintain optimal serotonin levels, it's worth eating tryptophan-rich foods such as eggs, cheese, tofu, nuts, pineapple, turkey, red meat and salmon.

It's also recommended to include complex carbohydrates and sources of omega-3 in your diet to support hormonal health.

Physical exercise 

Regular physical activity has been linked to an increase in the amount of serotonin and dopamine in the brain and contributes to a good mood. Exercise also influences the availability of tryptophan and therefore has an indirect effect on serotonin synthesis.

Exposure to natural light 

Spending time in natural light can help regulate serotonin levels in the body. Bright light – whether from the sun or another source – stimulates the retina and sends a signal to the brain to produce more serotonin.

This is why treatment for seasonal affective disorder often includes light therapy or exposure to sunlight.

Supplements

Certain supplements such as tryptophan, magnesium or B vitamins can influence serotonin levels in the body. Bear in mind, however, that serotonin is closely bound up with your emotional and mental health – so don't take any supplements or medication that can affect brain chemistry without medical advice.

Disorders linked to serotonin and the menstrual cycle 

Disorders linked to serotonin, particularly a drop in its levels in the body, have a direct effect on behaviour and mental health.

In women who suffer from serotonin-related disorders, symptoms can worsen when large fluctuations in oestrogen and progesterone alter serotonin levels in the body across the menstrual cycle. Such disorders may include:

• Premenstrual dysphoric disorder (PMDD): a more severe form of premenstrual syndrome that causes pronounced mood changes 1–2 weeks before menstruation.
• Premenstrual syndrome (PMS): involves a range of physical and emotional symptoms that occur before menstruation, including mood swings, exhaustion and irritability.
• Anxiety: serotonin plays an important role in regulating mood and anxiety, and reduced activity has been linked to higher levels of anxiety.
• Endocrine imbalances: these can directly affect serotonin levels and cause mood changes, anxiety and depression.

Frequently asked questions about serotonin 

It can be a real challenge to understand your body and yourself when you feel your mood is changing out of nowhere. Serotonin plays an essential role in emotional and physical balance, and hormonal changes – particularly those driven by your cycle – can have a direct effect on its levels. That's why we've gathered some of the most common questions about serotonin and how it affects you, and we hope the answers bring you a little more calm and clarity.

What is the connection between serotonin and premenstrual syndrome? 

Before menstruation, oestrogen levels fall and progesterone levels rise – and both hormonal changes have the same effect on serotonin, namely a drop in its levels.

Low serotonin levels in the premenstrual phase have been linked to symptoms such as irritability, sadness, anxiety and food cravings, and contribute to the development of premenstrual syndrome (PMS).

What role does oestrogen play in serotonin production? 

Oestrogen helps raise serotonin levels by stimulating production and increasing the sensitivity of receptors in the brain. When oestrogen levels fall, as they do in the luteal phase, serotonin levels fall too, affecting mood.

What is PMDD and how does it differ from PMS? 

PMDD (premenstrual dysphoric disorder) is a more severe form of premenstrual syndrome (PMS) and involves a more pronounced sensitivity to fluctuations in oestrogen, progesterone and serotonin.

Broadly speaking, PMS involves moderate physical and emotional symptoms such as irritability, lack of motivation and mood swings. PMDD, by contrast, is associated with intense mood disturbances, such as severe low mood, marked irritability and anxiety, which significantly disrupt daily life.

Why do some women become more anxious during menstruation? 

During menstruation, oestrogen and progesterone levels reach their lowest point, which can also keep serotonin at a low level. This encourages the onset of anxiety, which can in turn be intensified by period pain, exhaustion and other typical menstrual complaints.

How does stress affect serotonin levels? 

Chronic stress impairs brain function and can lead to reduced serotonin production. Since cortisol levels rise during stressful periods, an excess of this hormone may disrupt the brain's chemical balance and affect serotonin activity.

How are serotonin levels measured in the body?

Serotonin can be measured using blood tests, but these don't always accurately reflect serotonin levels in the brain. Urine tests don't reliably capture the amount of serotonin either. For this reason, diagnosing imbalances usually requires working with a specialist and carefully monitoring symptoms, rather than relying on laboratory measurements.

Image source: Pexels.com