Sleeping badly before your period is not always "stress".

It is also not always anxiety, lack of discipline, or one isolated bad night.

For many women, the night changes with the hormonal phase. Some notice it as lighter sleep. Others as waking up at 3 in the morning. Others as heat, sweating, irritability, unusual hunger, or a feeling that is hard to explain: the body is tired, but the nervous system will not come down.

The biology behind that pattern is more interesting than generic sleep advice. In the luteal phase, after ovulation, progesterone rises. Basal body temperature also usually rises. And for that night to feel stable, the body needs another signal: darkness.

That signal is called melatonin.

Melatonin is not just the sleep hormone

Melatonin is often reduced to one sentence: "the hormone that makes you sleepy." That is incomplete.

Melatonin is the endocrine signal of darkness. It tells the body that biological night has arrived. Not only because the clock shows a certain time, but because the retina stopped receiving enough light, the suprachiasmatic nucleus adjusted circadian output, and the pineal gland began producing melatonin.

In other words: melatonin does not appear because you "want to sleep." It appears when the body interprets real darkness.

That matters because the reproductive system does not live separately from the circadian clock. The ovary, the corpus luteum, temperature, cortisol, and sleep operate inside a temporal architecture. If the night signal is low, delayed, or fragmented, the body can spend hours in bed without receiving a complete nighttime hormonal signal.

This is where the connection with progesterone begins.

Progesterone, temperature, and a more sensitive night

After ovulation, the corpus luteum produces progesterone. That progesterone prepares the endometrium, modulates the nervous system, and changes basal temperature.

That is why many women see a small increase in temperature after ovulation. It is not a coincidence. Progesterone has a thermogenic effect: it pushes the body toward a higher basal temperature.

The paradox is that to sleep well, the body also needs to dissipate heat. Normally, during the night, core temperature drops and melatonin helps facilitate that transition. In the luteal phase, then, the body has to coordinate two forces:

progesterone raising basal temperature;
melatonin organizing the night and supporting sleep.

When that coordination works, progesterone can feel like calm, deeper sleep, or lower excitability. But when the night is disrupted by light, screens, stress, a late dinner, alcohol, caffeine, heat, or awakenings, the same luteal phase can feel different.

Not because progesterone is "bad". Because progesterone needs context.

The silent bridge: allopregnanolone

Part of progesterone is converted into allopregnanolone, a neurosteroid that modulates the GABA-A receptor, one of the brain's calming systems.

In simple language: progesterone does not only act in the uterus or ovary. It can also transform into a signal that changes how the nervous system feels.

For some women, that pathway feels like more stable sleep. For others, especially if there is premenstrual sensitivity, abrupt neurosteroid shifts, inflammation, stress, or fragmented sleep, it can feel like the opposite: irritability, nighttime anxiety, or "wired-tired" insomnia.

This point explains why universal advice fails. Two women can be in the luteal phase, have progesterone in range, and experience completely different nights. One may feel calm. Another may feel activated. The difference may be in the circadian, thermal, inflammatory, and neurological context.

What the science is beginning to show

A study by Greendale and colleagues in the Journal of the Endocrine Society analyzed melatonin patterns during the menstrual cycle and after menopause. It found that in premenopausal women, the nighttime urinary metabolite of melatonin had a cyclical pattern, with a peak around day 17. In postmenopausal women, levels were lower.

This does not mean we can read your cycle through melatonin. It means something more precise: the darkness signal and hormonal state appear to be in conversation.

Another study, published in Journal of Pineal Research, showed in human luteal cells that melatonin may protect progesterone production under oxidative stress. And recent studies in assisted reproduction have explored how melatonin relates to the follicular microenvironment, oxidative stress, and some markers of reproductive quality.

We have to be very precise here: this does not prove that taking melatonin improves fertility, sleep, or progesterone in all women. It does not justify a universal recommendation.

What it does do is open a useful hypothesis: biological night may be part of the context in which the body produces, uses, and feels progesterone.

Perimenopause: when the night warns you before the calendar does

For Carmen, 47 years old, this conversation is especially important.

Perimenopause usually does not begin as a clean hormonal blackout. It begins as variability. One cycle you ovulate, another you do not. One luteal phase feels normal, another breaks apart. One week you sleep well, another you wake up hot, anxious, or with your heart racing.

Estradiol can rise and fall. Progesterone can become more intermittent because ovulation is no longer as consistent. Nighttime temperature can become less predictable. And circadian amplitude, including the melatonin signal, can decline with age and the hormonal transition.

That is why some women feel that "the night changed" before the cycle disappears.

It is not just insomnia. It may be an early signal of uncoupling: sleep, temperature, progesterone, melatonin, cortisol, and the nervous system no longer moving in the same direction.

The Lua Labs hypothesis: LMPS

Lua Labs proposed a research biomarker called LMPS, for Luteal Melatonin-Progesterone Synchrony Score.

It does not measure melatonin. It does not measure progesterone. It does not diagnose anything.

The idea is more cautious: to study whether nighttime luteal-phase synchrony could, in the future, be inferred through longitudinal signals such as:

sleep regularity;
average sleep and wake times;
awakenings or minutes awake at night;
basal temperature or nighttime temperature from a wearable;
luteal symptoms such as irritability, anxiety, non-restorative sleep, or nighttime heat;
timing of dinner, caffeine, alcohol, and screens;
hormonal phase and life stage.

The point is not to tell you "your melatonin is low." The point is to notice whether your luteal phase changes when your night loses coherence.

A single night says little. Three cycles begin to tell a story.

The question is not "which hormone am I missing"

Wellness culture often turns every symptom into a missing molecule. You slept badly: low melatonin. You are anxious: low progesterone. You wake up hot: low estrogen.

The body is rarely that simple.

The more useful question is usually:

What pattern repeats?
In which phase does it appear?
What happened with sleep, food, light, stress, and temperature?
Does that pattern change in perimenopause?

That is where a longitudinal hormonal intelligence app can offer something different from a period tracker. Not telling you that you are on day 23. Helping you understand what tends to happen in your body when phase, food, sleep, and symptoms align or misalign.

Lua does not replace medical care. It does not diagnose low progesterone, melatonin deficiency, PCOS, perimenopause, or sleep disorders.

But it can help you build the part that almost never makes it into the consultation: a daily, accumulated story of how your body changes over time.

Because your sleep does not live separately from your hormones.

And your hormones do not live separately from the night.

This article summarizes peer-reviewed scientific evidence for educational purposes. It does not replace individual medical evaluation, diagnosis, or treatment. If you have persistent insomnia, intense hot flashes, abrupt cycle changes, suspected perimenopause, or symptoms that affect your daily life, consult a healthcare professional.

Sources

Greendale GA, Witt-Enderby PA, Karlamangla AS, et al. "Melatonin Patterns and Levels During the Human Menstrual Cycle and After Menopause." Journal of the Endocrine Society (2020). https://doi.org/10.1210/jendso/bvaa115
Taketani T, Tamura H, Takasaki A, et al. "Protective role of melatonin in progesterone production by human luteal cells." Journal of Pineal Research (2011). https://doi.org/10.1111/j.1600-079X.2011.00878.x
Wu C, Huang J. "Effects of melatonin as an adjuvant treatment on assisted reproductive outcomes in infertile women: a systematic review and meta-analysis." Frontiers in Reproductive Health (2025). https://doi.org/10.3389/frph.2025.1680984
Hu X, Yin C, Yang Y, et al. "From nighttime light exposure to menstrual health: a review of light-at-night disruptions on circadian rhythm and reproductive hormones." Frontiers in Reproductive Health (2026). https://doi.org/10.3389/frph.2026.1738574
Hosenfeld CS, Herson PS, Spencer RL. "Progesterone and Sleep: A Preclinical Review." Endocrinology (2025). https://doi.org/10.1210/endocr/bqaf047