Understanding Your Hormones: Estrogen, Progesterone, and the Chemistry of How You Feel

Here is something most of us were never told: the hormones that drive your menstrual cycle do not just handle reproduction. They touch nearly every system in your body -- your brain, your bones, your heart, your gut, your skin, your sleep. They influence how you process emotions, how clearly you think, how deeply you rest, how sensitively you perceive pain, and how readily you feel joy.

Estrogen and progesterone are not background noise. They are conductors.

And yet, most people who menstruate have only a vague understanding of what these hormones actually do. We know they exist. We know they "fluctuate." We might associate them with PMS or pregnancy. But the full picture -- how they work, what they affect, why their rise and fall shapes so much of daily experience -- is rarely taught in any meaningful way.

This article is an attempt to change that. Not with clinical jargon or biochemistry textbook density, but with the kind of clarity that actually helps you understand why you feel the way you feel.

This article is educational, not medical advice. Hormonal health is complex and individual. If you have concerns about your hormone levels or symptoms, please work with a healthcare provider.

The Hormonal Cast: Who Does What

Before diving deep into estrogen and progesterone, it helps to see the full ensemble. Your menstrual cycle involves several hormones working in concert:

| Hormone | Produced By | Primary Role |

|---------|------------|--------------|

| Estrogen (primarily estradiol) | Ovaries (follicles), also adrenal glands and fat tissue | Builds uterine lining, supports mood and cognition, maintains bone density, affects skin and cardiovascular health |

| Progesterone | Ovaries (corpus luteum after ovulation) | Maintains uterine lining for potential pregnancy, promotes calm and sleep, raises body temperature |

| Follicle-Stimulating Hormone (FSH) | Pituitary gland (brain) | Stimulates ovarian follicles to develop |

| Luteinizing Hormone (LH) | Pituitary gland (brain) | Triggers ovulation |

| Testosterone | Ovaries and adrenal glands | Supports libido, energy, muscle maintenance, and assertiveness |

| Gonadotropin-Releasing Hormone (GnRH) | Hypothalamus (brain) | The upstream signal that starts the whole cascade by telling the pituitary to release FSH and LH |

The system works as a feedback loop. The brain monitors hormone levels in the blood and adjusts its signals accordingly. When estrogen reaches a certain level, the brain responds by triggering the LH surge that causes ovulation. When progesterone drops at the end of the luteal phase, the brain registers that pregnancy has not occurred and restarts the cycle.

It is elegant. It is also deeply interconnected with everything else happening in your body, which is why hormonal shifts can feel so all-encompassing.

Estrogen: The Hormone That Builds

Estrogen is the most discussed reproductive hormone, and for good reason -- its influence extends far beyond the uterus. When people say "estrogen," they are usually referring to estradiol (E2), which is the most potent and abundant form during reproductive years. Two other forms exist: estrone (E1), which is dominant after menopause, and estriol (E3), which is primarily produced during pregnancy.

What Estrogen Does in Your Body

In the reproductive system:

Stimulates the growth and thickening of the uterine lining (endometrium) during the follicular phase
Promotes the production of cervical mucus that facilitates sperm transport around ovulation
Supports the maturation of ovarian follicles

In the brain:

Increases serotonin production and receptor sensitivity -- serotonin is a neurotransmitter associated with mood stability, well-being, and calm
Supports dopamine activity -- dopamine is linked to motivation, pleasure, and reward
Enhances verbal memory and learning
Promotes neuroplasticity (the brain's ability to form new connections)
May have neuroprotective effects, which is one reason researchers are studying the relationship between menopause and cognitive changes

In the body:

Maintains bone density by inhibiting the cells that break down bone (osteoclasts)
Supports cardiovascular health by helping maintain healthy cholesterol ratios and blood vessel flexibility
Promotes collagen production in the skin, contributing to elasticity and hydration
Influences fat distribution (estrogen tends to direct fat storage to the hips and thighs rather than the abdomen)
Affects insulin sensitivity and glucose metabolism
Plays a role in the health of the urinary tract and vaginal tissue

The Estrogen Wave: How It Moves Through Your Cycle

Estrogen is not a constant. It follows a distinct pattern each cycle:

Menstruation: Estrogen is at its lowest. This hormonal quiet is part of why the early days of your period can feel stripped-down and raw.

Follicular phase: Estrogen begins to rise as ovarian follicles develop. This rise is gradual at first, then accelerates. As estrogen climbs, so does serotonin production. This is the biological basis for the mood lift, increased confidence, and social energy that many people experience as their period ends.

Ovulation: Estrogen peaks sharply in the day or two before ovulation. This peak is what triggers the LH surge that causes the egg to release. At this point, many people feel their most energetic, articulate, and connected.

Luteal phase: Estrogen drops after ovulation, then has a smaller secondary rise in the mid-luteal phase (driven by the corpus luteum), before falling again toward the end of the cycle. This late-cycle estrogen withdrawal, combined with the progesterone drop, is a major contributor to PMS symptoms.

What Estrogen Withdrawal Feels Like

Because estrogen so directly supports serotonin and dopamine activity, its withdrawal can produce effects that mirror, in miniature, the experience of withdrawing from a mood-supporting medication:

Low mood or sadness
Anxiety or heightened worry
Irritability and a shorter fuse
Brain fog or difficulty concentrating
Disrupted sleep
Increased pain sensitivity
Reduced motivation

This is not "all in your head." It is neurochemistry. The same brain that felt sharp and optimistic when estrogen was high is now operating with less serotonin support. Understanding this does not make the feelings disappear, but it can prevent you from layering self-judgment on top of an already difficult experience.

Progesterone: The Hormone That Settles

If estrogen is the builder, progesterone is the maintainer. Its name comes from "pro-gestation" -- supporting pregnancy. But progesterone's effects extend well beyond the uterus, and understanding it is key to understanding the second half of your cycle.

What Progesterone Does in Your Body

In the reproductive system:

Transforms the uterine lining from a growing layer into a spongy, nutrient-rich environment capable of supporting a fertilized egg
Raises basal body temperature by about 0.3 to 0.6 degrees Celsius after ovulation (this temperature shift is how basal body temperature tracking confirms that ovulation has occurred)
Thickens cervical mucus, creating a plug that protects the uterus

In the brain:

Progesterone is metabolized into a compound called allopregnanolone (ALLO), which acts on GABA receptors -- the same receptors targeted by anti-anxiety medications and alcohol
This GABA activity produces a calming, sedative-like effect
Supports deeper sleep in the early and mid-luteal phase
Can contribute to drowsiness, slower cognitive processing, and a feeling of being "in a fog" when levels are high

In the body:

Relaxes smooth muscle (which can slow digestion, contributing to bloating and constipation)
Can increase appetite and cravings, particularly for carbohydrate-rich and calorie-dense foods -- this is thought to be the body's way of ensuring adequate energy if pregnancy has occurred
Promotes fluid retention, contributing to bloating and breast tenderness
Has anti-inflammatory properties
Interacts with the immune system in complex ways

The Progesterone Wave: How It Moves Through Your Cycle

Progesterone has a simpler pattern than estrogen, but its effects are profound:

Menstruation and follicular phase: Progesterone is very low. It is essentially absent until ovulation occurs.

After ovulation: The corpus luteum (the structure left behind when the follicle ruptures) begins producing significant amounts of progesterone. Levels rise steadily over the first week after ovulation.

Mid-luteal phase: Progesterone reaches its peak, approximately 5 to 7 days after ovulation. This is when its calming effects are strongest -- and also when appetite increases, sleep deepens, and the nesting instinct many people describe tends to kick in.

Late luteal phase: If pregnancy does not occur, the corpus luteum degrades and progesterone production falls rapidly. This sharp drop is a primary trigger for menstruation and is heavily implicated in PMS symptoms.

What Progesterone Withdrawal Feels Like

The rapid decline of progesterone in the late luteal phase removes the calming GABA support that had been present for over a week. This withdrawal can produce:

Anxiety and restlessness (the chemical "blanket" has been pulled away)
Insomnia or disrupted sleep
Mood swings
Heightened emotional reactivity
Physical symptoms: cramping begins as the uterine lining prepares to shed

For people with PMDD (premenstrual dysphoric disorder), this progesterone withdrawal appears to trigger an abnormal sensitivity in the brain's response, leading to severe mood disruption that goes well beyond typical PMS. PMDD is a recognized clinical condition, and if your premenstrual experience is severe, treatment options exist.

Testosterone: The Forgotten Player

Testosterone is typically associated with male biology, but everyone produces it. In people who menstruate, testosterone is produced in smaller amounts by the ovaries and adrenal glands, and it plays a genuine role in the menstrual cycle experience.

What Testosterone Does

Libido: Testosterone is a primary driver of sexual desire. Its slight rise around ovulation contributes to the increase in libido many people notice mid-cycle.
Energy and motivation: Testosterone supports feelings of vitality, drive, and initiative.
Muscle and bone: It contributes to maintaining muscle mass and bone density.
Assertiveness and confidence: Some research suggests testosterone supports risk-taking, competitive drive, and social dominance behaviors.

Testosterone Through the Cycle

Testosterone levels fluctuate less dramatically than estrogen and progesterone, but they do shift:

There is a small but meaningful rise just before and during ovulation
Levels tend to be slightly higher in the follicular phase overall
They are generally lower during the luteal phase

The ovulatory bump in testosterone, combined with peak estrogen, is part of why the days around ovulation often feel like the most confident, energetic, and socially bold point in the cycle.

The Brain-Hormone Connection: Why You Feel What You Feel

Understanding hormones as purely reproductive misses the bigger picture. The brain is one of the most hormone-sensitive organs in the body, and the cyclical changes in estrogen and progesterone directly shape neurotransmitter activity.

Estrogen and Serotonin

Estrogen promotes serotonin in multiple ways:

It increases tryptophan hydroxylase, the enzyme that produces serotonin
It decreases the activity of monoamine oxidase (MAO), an enzyme that breaks serotonin down
It increases the density of serotonin receptors in certain brain regions

This is why rising estrogen in the follicular phase tends to correlate with improved mood, and why falling estrogen in the late luteal phase can produce something that looks and feels a lot like a depressive episode.

Progesterone and GABA

Progesterone's metabolite, allopregnanolone, is one of the most potent natural modulators of the GABA-A receptor. GABA is the brain's primary inhibitory neurotransmitter -- it reduces neuronal excitability and promotes calm.

When progesterone is high (mid-luteal phase), GABA activity increases. This can produce:

A sense of calm or even mild sedation
Deeper, more restorative sleep
Reduced anxiety

When progesterone drops (late luteal phase), GABA support is withdrawn. For most people, this is uncomfortable but manageable. For people with heightened sensitivity to this withdrawal, it can produce:

Severe anxiety
Panic attacks
Insomnia
Depressive symptoms
Emotional volatility

Estrogen and Dopamine

Estrogen also interacts with the dopamine system, which governs motivation, reward, and pleasure. Rising estrogen during the follicular phase supports dopamine activity, which may contribute to:

Increased motivation and goal-directed behavior
Greater sense of reward from social interaction and achievement
Enhanced ability to experience pleasure

The dopamine connection may also explain why some people experience cravings and comfort-seeking behavior during the luteal phase, when estrogen (and by extension, dopamine support) is declining. The craving for chocolate or carbs may, in part, be an unconscious attempt to boost neurotransmitter activity through food.

Hormones Beyond the Cycle: Other Systems They Touch

Bone Health

Estrogen is critical for maintaining bone density. It inhibits osteoclasts (cells that break down bone tissue), which is why the decline in estrogen during perimenopause and menopause is associated with an increased risk of osteoporosis. This is also why prolonged absence of periods (amenorrhea) in younger people is a concern -- low estrogen over time can compromise bone health.

Cardiovascular Health

Before menopause, estrogen appears to have a protective effect on the cardiovascular system. It supports healthy cholesterol profiles, promotes blood vessel flexibility, and has anti-inflammatory properties. The loss of this protection after menopause is one factor in the increased cardiovascular risk that postmenopausal people face.

Gut Health

Progesterone relaxes smooth muscle, including the muscles of the digestive tract. This is why many people experience slower digestion, bloating, and constipation during the luteal phase. Conversely, the drop in progesterone at the start of menstruation can speed up digestion, sometimes leading to loose stools or diarrhea during the period. These are not mysterious symptoms -- they are predictable hormonal effects.

Skin

Estrogen promotes collagen production, skin hydration, and wound healing. Skin tends to look its best when estrogen is high (late follicular phase and ovulation). The hormonal shifts of the late luteal phase -- combined with a relative increase in androgen influence when estrogen and progesterone fall -- can contribute to premenstrual breakouts. This is the same mechanism behind hormonal acne patterns.

Sleep

Both estrogen and progesterone influence sleep architecture:

Progesterone promotes sleep through its GABA-enhancing effects. Sleep quality often improves in the early and mid-luteal phase.
Estrogen supports REM sleep and may reduce the number of nighttime awakenings.
The late luteal phase and early menstruation, when both hormones are low, is when sleep disturbances are most commonly reported.

Immune Function

Hormones modulate the immune system in complex ways. Some research suggests that immune function shifts across the cycle -- with a more pro-inflammatory state during menstruation and a more immune-tolerant state after ovulation (which makes biological sense, as the body would need to avoid rejecting a fertilized egg). This may be why some people notice that they are more susceptible to illness at certain points in their cycle, or why autoimmune conditions can flare cyclically.

Hormonal Disruption: When the System Goes Off-Key

The hormonal system is resilient, but it is not invulnerable. Several factors can disrupt the hormonal patterns described above:

Stress

Chronic stress elevates cortisol, which can suppress the hypothalamic-pituitary-ovarian axis that drives the menstrual cycle. High cortisol can:

Delay or suppress ovulation
Shorten the luteal phase
Cause irregular or absent periods
Amplify PMS symptoms

The stress-hormone connection is one reason why major life changes, grief, job loss, or sustained anxiety can throw your cycle off even when nothing else has changed.

Under-Fueling

The body requires adequate caloric intake -- particularly adequate fat intake -- to produce reproductive hormones. Severe caloric restriction, excessive exercise without adequate fueling, or eating disorders can lead to hypothalamic amenorrhea, where the brain effectively shuts down the reproductive system because it determines that conditions are not safe for pregnancy.

This is not the body being dramatic. It is the body being protective. But the hormonal consequences extend beyond fertility -- bone density, cardiovascular health, mood, and cognitive function are all affected.

Endocrine Disruptors

Certain chemicals found in plastics, pesticides, personal care products, and food packaging can mimic or interfere with hormones. Research on endocrine disruptors is ongoing, but some compounds -- including BPA, phthalates, and certain pesticides -- have been associated with hormonal disruption in both animal and human studies.

PCOS

Polycystic ovary syndrome is one of the most common hormonal conditions, affecting an estimated 8 to 13 percent of reproductive-age people (many of whom are undiagnosed). PCOS involves an imbalance of reproductive hormones -- often elevated androgens and insulin resistance -- that can disrupt ovulation, cause irregular periods, and produce a range of symptoms including acne, unwanted hair growth, weight gain, and fertility challenges.

Thyroid Disorders

The thyroid gland produces hormones that regulate metabolism, and thyroid dysfunction (both hypothyroidism and hyperthyroidism) can significantly affect the menstrual cycle. Thyroid disorders are far more common in people who menstruate and can cause heavy periods, light periods, irregular cycles, or absent periods.

What Testing Can (and Cannot) Tell You

Hormone testing -- typically through blood work -- can provide useful information, but it comes with important caveats:

Timing matters. Hormone levels change throughout the cycle, so a single blood draw only captures a snapshot. Testing progesterone on Day 3 of your cycle, for example, will always show a low result because progesterone is supposed to be low at that point.
"Normal" ranges are wide. What is considered a normal estrogen or progesterone level varies significantly between individuals. A level that causes symptoms in one person may be fine for another.
Context matters more than numbers. A good clinician interprets hormone levels in the context of your symptoms, history, and overall health -- not as standalone data points.
Some conditions are diagnosed clinically, not just by labs. PMDD, for example, is diagnosed based on symptom patterns, not hormone levels (because hormone levels in people with PMDD are often technically "normal" -- the issue is how the brain responds to normal fluctuations).

If you suspect a hormonal issue, advocate for testing that makes sense for your situation, and work with a provider who is willing to listen to your experience alongside the lab results.

Hormones Across the Lifespan

The hormonal patterns described in this article are specific to the reproductive years, but hormones continue to matter -- and shift -- throughout life:

Puberty

The menstrual cycle begins when the hypothalamic-pituitary-ovarian axis matures enough to produce the hormonal cascade that drives ovulation. Early cycles are often irregular as this system calibrates, and it can take several years for a regular pattern to establish.

Pregnancy and Postpartum

Pregnancy involves a dramatic hormonal shift. Progesterone and estrogen rise to levels far beyond anything seen in the menstrual cycle, supported first by the corpus luteum and then by the placenta. After delivery, these hormones crash precipitously, which is one of the factors contributing to postpartum mood changes. Breastfeeding keeps certain hormones elevated (particularly prolactin) and can suppress the return of the menstrual cycle for months.

Perimenopause

The transition toward menopause typically begins in the mid-to-late 40s (though it can start earlier) and involves increasingly erratic hormonal patterns. Estrogen levels become unpredictable -- sometimes surging higher than during reproductive years, sometimes dropping sharply. Cycles become irregular. Symptoms can include hot flashes, night sweats, mood changes, sleep disruption, brain fog, and changes in menstrual flow.

Perimenopause is not a switch that flips. It is a gradual, often years-long transition that can be profoundly disorienting -- especially for people who have not been told what to expect.

Menopause

Menopause is defined as 12 consecutive months without a menstrual period. At this point, the ovaries have essentially ceased producing the cyclical estrogen and progesterone that drove the menstrual cycle. Post-menopausal hormonal changes affect bone health, cardiovascular risk, brain function, metabolism, and more. Hormone replacement therapy (HRT) is one option for managing these effects, and the conversation around its risks and benefits has evolved significantly in recent years.

The Knowledge Gap -- And Why It Matters

Here is the uncomfortable truth: most people who menstruate know less about their own hormones than they know about their phone settings. This is not a personal failure. It is a systemic one. Hormonal health education has been inadequate for generations -- cursory in school, often dismissive in clinical settings, and surrounded by cultural messages that treat hormonal experiences as either too embarrassing to discuss or too trivial to take seriously.

The result is that millions of people spend decades experiencing mood shifts, energy changes, sleep disruptions, pain, and cognitive fluctuations without understanding the biological mechanisms driving them. They blame themselves. They wonder if something is wrong with them. They push through when their body is asking them to rest, and they rest when their body is ready to run.

Understanding your hormones does not fix everything. But it reframes the conversation. It moves you from "what is wrong with me?" to "what is happening in my body right now, and what does it need?"

That shift -- from confusion to comprehension -- is where real self-knowledge begins.

Where Gliss Fits In

Gliss was designed around a simple premise: the more you understand your hormonal rhythms, the better you can navigate your days.

The app does not just track your period. It learns your patterns -- how your mood, energy, sleep, and symptoms map to your unique hormonal cycle over time. It surfaces insights that are specific to you, not generic predictions pulled from population averages. And it does this in language that is warm and clear, not clinical and intimidating.

Because understanding your hormones should not require a biochemistry degree. It should feel like a conversation with someone who has been paying attention.

Your rhythm, revealed.

This article is for educational purposes and is not a substitute for professional medical advice. If you have questions about your hormones or symptoms, please consult a qualified healthcare provider.