Reviewed by:
Dr. Myrna Assaf — Gynecologist specializing in menopause and hormonal disorders, with a focus on intimate health.
Dr. Patricia Núñez de Aysa — Medical expert in Longevity, specialist in rehabilitation and non-surgical traumatology.
Dr. Joel Cuesta Gascón — Medical expert in sports medicine, rehabilitation, and nutrition.
Last updated: May 2026.

In 30 seconds

• "Women are cyclical" is not a metaphor or a New Age cliché. It's a biological reality with neurological, metabolic, and emotional foundations.
• The menstrual cycle has 4 phases (menstrual, follicular, ovulatory, and luteal) regulated by estrogens, progesterone, LH, and FSH, interacting with serotonin, dopamine, cortisol, and GABA.
• These fluctuations don't just affect the uterus: they change energy, sleep, cognition, mood, and stress tolerance.
• Understanding your cycle isn't about labeling your identity; it's useful clinical information. And when something goes awry, it's a signal that deserves attention, not normalization.

"We are cyclical" is not an excuse: it's biology

The phrase circulates on social media, in consultations, in conversations between friends. Sometimes it's said with admiration, and other times, let's be honest, it sounds a bit like an excuse or a New Age cliché. But behind that idea lies real, concrete, and fascinating biology.

We are cyclical. And it's not a metaphor.

Throughout the menstrual cycle — which normally lasts between 21 and 35 days — the body goes through four distinct phases, each orchestrated by a different combination of hormones. These hormonal changes don't stay in the uterus: they affect the brain, the nervous system, mood, concentration ability, physical energy, and even how we process stress.

It's not that you're a different person one week. It's that the biological ground you live on changes every week. And that has real consequences.

"The cycle is not just reproductive. It is neurological, metabolic, and emotional."

The four main hormones

To understand what happens in each phase, you first need to know the main players that direct the process:

Estrogens

Primarily produced by the ovaries. They support energy peaks, mental clarity, sociability, and motivation in the first half of the cycle. They modulate serotonin and dopamine production in the brain.

Progesterone

The protagonist of the second half. It has a calming and sedative effect on the nervous system because it acts on GABA receptors, the same ones used by anxiolytics. But when it drops sharply at the end of the cycle, it can drag down mood with it.

LH and FSH (luteinizing and follicle-stimulating)

These hormones coordinate follicle development and trigger ovulation. Their peak marks the midpoint of the cycle and has direct effects on energy and libido.

These hormones don't work in isolation: they interact with serotonin, dopamine, cortisol, and GABA, the neurotransmitters that regulate mood, motivation, and stress response. When hormones fluctuate, these brain messengers also shift. This is why the cycle is felt not only physically but also mentally.

Quick chart: the 4 phases of the cycle

🌑 Menstrual Phase (approximately days 1-5)

The cycle begins with menstruation. Estrogen and progesterone levels are at their lowest point of the month, and this is noticeable. The brain has reduced access to serotonin, which can lead to increased sadness, irritability, or a need for withdrawal.

Something interesting happens in these first few days: while the body goes through this renewal process, thoughts tend to become introspective. Many women describe more clarity for reviewing what isn't working, for making decisions that had been postponed, or for wanting to be alone without having to explain themselves.

It's not drama or hypersensitivity. It's that the veil of social activation maintained by estrogens lifts for a moment, and what lies beneath comes to the surface.

What usually appears: tiredness, increased need for warmth and rest, lower tolerance for noise and social plans, more reflective and less executive thinking.

🌒 Follicular Phase (approximately days 6-13)

Once menstruation ends, estrogen levels begin to gradually rise. And with them, almost everything improves. Energy increases, sleep is usually more restorative, appetite stabilizes, and a renewed desire to start new things appears.

In the brain, estrogens boost the production of serotonin and dopamine: well-being and motivation. This is the phase where many women feel most like themselves: with ideas, initiative, a desire to socialize, and to tackle projects that at other times in the cycle seemed too big.

Thinking becomes more convergent and action-oriented. There's greater ease in learning, public speaking, and negotiation. This is no coincidence: the hippocampus — the brain area related to memory and learning — is especially sensitive to estrogens.

What usually appears: optimism, mental clarity, creativity, desire to connect, increased tolerance for physical exertion.

🌕 Ovulatory Phase (approximately days 14-16)

The LH peak coincides with the time of highest energy in the cycle for many women. Estrogen levels are at their peak, and there's also a small surge in testosterone, which translates into greater confidence, more initiative, and increased libido.

From a communicative perspective, it's striking: several studies have observed that during ovulation, people tend to speak more fluently, be more persuasive, and perceive themselves as more attractive. It's not vanity; it's neurochemistry.

It's also the time when the body—and mind—are more outwardly oriented. More social openness, more willingness to take risks, more capacity to lead. If there's something important to do that requires energy and presence, this phase is usually a good ally.

What usually appears: peak energy and vitality, increased extroversion, confidence, ease in making quick decisions.

🌘 Luteal Phase (approximately days 17-28)

After ovulation, the follicle that released the egg becomes a corpus luteum and begins to produce progesterone. This hormone has a calming and sedative effect on the nervous system—it acts on GABA receptors, as we've seen—but it has a dual nature.

First part of the luteal phase

In the first few days after ovulation, many women feel a kind of pleasant stillness: less rush, greater capacity for tasks requiring sustained concentration, a greater tendency toward detailed thinking. Creativity usually becomes richer and less urgent: more appropriate for deep work than for brainstorming.

Second part: the home stretch

When progesterone and estrogens drop together in the last 5-7 days before your period, the body goes into an alert state. Serotonin drops, sensitivity to cortisol increases, and what many women know well appears: irritability, anxiety, sadness, hypersensitivity, carbohydrate cravings, fatigue, difficulty sleeping well.

This isn't inevitably PMS, but it is physiology. Whether this period is mild, moderate, or incapacitating depends on many factors — nutrition, sleep, chronic stress, systemic inflammation, hormonal history — and not on whether one is "dramatic" or not.

We discuss this in depth in this article: Premenstrual syndrome: what worsens it and how to realistically alleviate it.

What usually appears: first part: calm and concentration. Second part: increased emotional sensitivity, fatigue, need for more self-care.

Why does this matter?

It's not so that we make the cycle an identity or turn it into an excuse for anything. It's so that we stop interpreting fluctuations as symptoms of something wrong with us.

When a woman feels more tired, more sensitive, or less sociable on certain days of the month, the usual cultural response is for her to try harder, not exaggerate, or simply manage it. And that ignores that there is a very concrete biological reason behind what she is feeling.

Knowing one's own cycle — not the one in books, but the real one, with its peculiarities — allows us to anticipate moments of greater vulnerability, plan better, ask for support when needed, and, above all, stop judging ourselves by the same standard every day of the month.

"It's not that you're 'weird' that week. It's that your biology is different that week."

The cycle as a vital sign

In medicine, there's a growing recognition of a concept: the menstrual cycle is a vital sign. Just like blood pressure, heart rate, or temperature, it reflects how the body is functioning overall.

When the cycle is altered — when PMS is debilitating, when fatigue in certain phases is paralyzing, when regularity disappears, when very heavy or very light bleeding occurs — the body is signaling something that deserves attention, not normalization.

Some reasons to consult a professional:

• Consistently very irregular cycles (especially outside of adolescence and perimenopause).
• Very heavy bleeding that affects your quality of life.
• PMS or dysmenorrhea (menstrual pain) that prevents you from living normally several days a month.
• Suspicion of PCOS (Polycystic Ovary Syndrome), endometriosis, or adenomyosis.
• Loss or absence of menstruation (amenorrhea) with no clear cause.
• Very marked cyclic mood changes (rule out PMDD).
• New symptoms starting at age 35-40 (possible perimenopause).

Cyclicality is not weakness

The idea that women are less reliable or less productive because they are cyclical comes from centuries of equating variability with instability. But hormonal variability is not a design flaw. It is a complex system that responds, adapts, and, when well cared for, functions with extraordinary precision.

Understanding this system — as healthcare professionals, as patients, as people — is the first step to stop working against it and start working with it.

And that, without a doubt, deserves more conversation than we are having.

When the cycle needs support

Knowing the phases is the first step. Supporting them well is the next. This includes the basics — sleep, nutrition, movement, stress management — and, when necessary, specific evidence-backed supports.

To support the cycle naturally, without blocking it, we formulated Cyklo: a combination of vitex agnus-castus, magnesium, vitamin B6, turmeric, ginger, omega-3, and piperine designed to support hormonal balance, reduce inflammation, and improve mood throughout the cycle. It is formulated by doctors and intended for continuous use.

If you have questions about your case, schedule a free medical consultation with our team (including an assessment with Dr. Myrna Assaf in gynecology when appropriate) or contact us via WhatsApp.

Frequently asked questions

Is it normal to experience mood swings throughout the cycle?

Yes, within a range. Mild variations in energy, sociability, libido, or focus are physiological. Changes that limit your daily life (deep sadness, intense anxiety, uncontrollable irritability) warrant evaluation, especially to rule out PMDD.

How long should a menstrual cycle last?

Between 21 and 35 days in adult women. Occasional variations are normal; sustained patterns outside this range warrant a medical review.

Can I train hard during any phase of the cycle?

Yes, but perceived performance changes. In the follicular and ovulatory phases, it is usually optimal; in the late luteal phase, it is advisable to listen to your body, lower intensities if needed, and prioritize recovery.

Does the birth control pill "eliminate" cyclicality?

Yes, combined pills inhibit the natural cycle and provide more stable hormone levels. This may be desirable for some women and not for others. It is a decision that should be made with informed consent and with a professional.

Why do I notice PMS more as I get older?

After 35-40 years of age, perimenopause usually begins, and cycles become more irregular and, in some women, more symptomatic. It is a good time to review your approach.

Can diet change how I experience my cycle?

Yes, very much so. Sufficient protein, fiber, omega-3, micronutrients (magnesium, vitamin D, B6), and avoiding ultra-processed foods and excessive alcohol are factors that clearly modulate cyclic symptoms.

Do I need to track my cycle?

It's not mandatory, but it helps a lot. Simple tracking (app or planner) for 2-3 cycles gives you valuable information about your real patterns: when symptoms appear, what makes them worse, and what helps you.

When will I notice the effects of a hormonal supplement like Cyklo?

Hormonal regulation is a gradual process. It is common to notice changes between the first and second cycle of consistent intake. Consistency is key: the endocrine system does not respond to isolated impulses.

Bibliographical references

• Reilly TJ, Patel S, Unachukwu IC, et al. The prevalence of premenstrual dysphoric and premenstrual syndrome: A systematic review and meta-analysis. J Affect Disord. 2024;356:135-147.
• Sundström-Poromaa I, Gingnell M. Menstrual cycle influence on cognitive function and emotion processing — from a reproductive perspective. Front Neurosci. 2014;8:380.
• Pletzer B, Harris TA, Scheuringer A, Hidalgo-Lopez E. The cycling brain: menstrual cycle related fluctuations in hippocampal and fronto-striatal activation. Neuropsychopharmacology. 2019;44(11):1867-1875.
• Schmalenberger KM, Tauseef HA, Barone JC, et al. How to study the menstrual cycle: Practical tools and recommendations. Psychoneuroendocrinology. 2021;123:104895.
• Diamond MP, Eichner A, Mortensen E, et al. Menstrual cycle, mood, and behavior. Womens Health (Lond). 2022;18:17455057221117315.
• Yonkers KA, Simoni MK. Premenstrual disorders. Am J Obstet Gynecol. 2018;218(1):68-74.
• ACOG Committee on Adolescent Health Care. The Menstrual Cycle as a Vital Sign. Committee Opinion No. 651.

Keep reading:

• Premenstrual syndrome: what worsens it and how to alleviate it
• Symptoms of menopause: what changes you might notice and how to support this stage