Hormones

Part 1

Your cycle

How your hormones move

Four hormones drive your cycle: FSH and LH from your brain, oestradiol and progesterone from your ovaries. Tap a phase, or slide across the chart to look day by day.

OestradiolProgesteroneLHFSH

Drag or tap across the chart to look day by day.

Each line is scaled to its own peak (= 1): you see each hormone's pattern, not the amount. Tap or slide for the real values: the median in 20 women measured daily.

Establishment of detailed reference values for luteinizing hormone, follicle stimulating hormone, estradiol, and progesterone during different phases of the menstrual cycle on the Abbott ARCHITECT analyzer.

Stricker R, Eberhart R, Chevailler MC, Quinn FA, Bischof P et al.

Clin Chem Lab Med 2006 · PMID 16776638

Temperature regulation in women: Effects of the menstrual cycle.

Baker FC, Siboza F, Fuller A

Temperature (Austin) 2020 · PMID 33123618 · PMCID PMC7575238

The balance between progesterone and oestradiol

In the chart each line is scaled to its own peak, so oestradiol and progesterone look equally large. Convert the values to the same unit and you see how strongly the balance shifts after ovulation: in the first half there's 1 to 4 times as much progesterone as oestradiol, in the second half 40 to 70 times. This prepares the womb lining. There's no single 'right' ratio, so always read your values together with your cycle day and symptoms.

Progesterone per oestradiol (median, same unit)

Early follicular 4×

Late follicular 1×

LH peak 4×

Early luteal 44×

Mid-luteal 73×

Late luteal 43×

Group median per phase: progesterone divided by oestradiol, both in nmol/L. In one woman this can differ a lot.

Establishment of detailed reference values for luteinizing hormone, follicle stimulating hormone, estradiol, and progesterone during different phases of the menstrual cycle on the Abbott ARCHITECT analyzer.

Stricker R, Eberhart R, Chevailler MC, Quinn FA, Bischof P et al.

Clin Chem Lab Med 2006 · PMID 16776638

Diagnosis and treatment of luteal phase deficiency: a Committee Opinion.

Practice Committee of the American Society for Reproductive Medicine and Practice Committee of the Society for Reproductive Endocrinology and Infertility

Fertil Steril 2026 · PMID 42414147

What if that shift doesn't happen?

Without ovulation, progesterone doesn't rise. Oestradiol then acts unopposed on the womb lining, often leading to irregular periods. Doctors call this 'unopposed oestrogen'; online it's often called oestrogen dominance. It's more common than you'd think: in about 1 in 12 cycles in healthy women, and more often in these situations:

Heavy training, eating too little

Half the cycles of exercising women had no ovulation or a short second half, against 4% in inactive women.

Perimenopause

In women aged 43 to 53, the share of cycles with ovulation fell from 81% to 65% over 3 years.

PCOS, thyroid and prolactin

Known causes of cycles without ovulation.

How to check. A progesterone test in the second half of your cycle shows whether you ovulated. One test can mislead, so repeat it if in doubt.

Increased androgen, anti-Müllerian hormone, and sporadic anovulation in healthy, eumenorrheic women: a mild PCOS-like phenotype?

Sjaarda LA, Mumford SL, Kissell K, Schliep KC, Hammoud AO et al.

J Clin Endocrinol Metab 2014 · PMID 24606085 · PMCID PMC4037725

High prevalence of subtle and severe menstrual disturbances in exercising women: confirmation using daily hormone measures.

De Souza MJ, Toombs RJ, Scheid JL, O'Donnell E, West SL et al.

Hum Reprod 2010 · PMID 19945961

Factors related to declining luteal function in women during the menopausal transition.

Santoro N, Crawford SL, Lasley WL, Luborsky JL, Matthews KA et al.

J Clin Endocrinol Metab 2008 · PMID 18285413 · PMCID PMC2386686

Evaluation and management of abnormal uterine bleeding in premenopausal women.

Sweet MG, Schmidt-Dalton TA, Weiss PM, Madsen KP

Am Fam Physician 2012 · PMID 22230306

Cleveland Clinic: high oestrogen

On the term oestrogen dominance

How your body clears hormones

Your body clears hormones every day, mainly through your liver, your bile and your gut. Your gut bacteria play a part: they can switch some oestrogen back on and send it back to your blood. In humans the evidence is still thin. In a study of 62 women, extra wheat bran lowered oestrogen; oat and corn bran did nothing. In a larger study of 250 women, a lot of fibre was linked to lower hormone levels and more cycles without ovulation. So more isn't always better.

Tap a step to learn more.

Simplified diagram of how your body clears oestrogen.

Estrogen-gut microbiome axis: Physiological and clinical implications.

Baker JM, Al-Nakkash L, Herbst-Kralovetz MM

Maturitas 2017 · PMID 28778332

Estrogen excretion patterns and plasma levels in vegetarian and omnivorous women.

Goldin BR, Adlercreutz H, Gorbach SL, Warram JH, Dwyer JT et al.

N Engl J Med 1982 · PMID 7144835

High-fiber diet reduces serum estrogen concentrations in premenopausal women.

Rose DP, Goldman M, Connolly JM, Strong LE

Am J Clin Nutr 1991 · PMID 1652197

Effect of daily fiber intake on reproductive function: the BioCycle Study.

Gaskins AJ, Mumford SL, Zhang C, Wactawski-Wende J, Hovey KM et al.

Am J Clin Nutr 2009 · PMID 19692496 · PMCID PMC2744625

No cycle is average

In over 600,000 cycles, only 13% lasted exactly 28 days. The average was 29.3 days, and mainly the first half varies: the phase after ovulation is fairly fixed at about 12 days. Normal is 21 to 35 days between periods, with 2 to 8 days of bleeding.

Study funded by a cycle app (Natural Cycles)

Real-world menstrual cycle characteristics of more than 600,000 menstrual cycles.

Bull JR, Rowland SP, Scherwitzl EB, Scherwitzl R, Danielsson KG et al.

NPJ Digit Med 2019 · PMID 31482137 · PMCID PMC6710244

Thuisarts (Dutch GP site): irregular periods

What is normal

What you notice, and what's a myth

After ovulation your temperature rises by 0.3 to 0.7 °C. In healthy women, sleep didn't change across the cycle, and most studies found no fixed link between mood and a phase. In the second half women eat a little more on average, but studies measure this in different ways.

Myth: everyone has a 28-day cycle with ovulation on day 14.
Myth: everyone is low or irritable before their period.
Myth: you burn far more calories before your period.

Menstrual Cycle Variations in Wearable-Detected Finger Temperature and Heart Rate, But Not in Sleep Metrics, in Young and Midlife Individuals.

Alzueta E, Gombert-Labedens M, Javitz H, Yuksel D, Perez-Amparan E et al.

J Biol Rhythms 2024 · PMID 39108015 · PMCID PMC11416332

Mood and the menstrual cycle: a review of prospective data studies.

Romans S, Clarkson R, Einstein G, Petrovic M, Stewart D

Gend Med 2012 · PMID 23036262

The Effect of the Menstrual Cycle on Energy Intake: A Systematic Review and Meta-analysis.

Tucker JAL, McCarthy SF, Bornath DPD, Khoja JS, Hazell TJ

Nutr Rev 2025 · PMID 39008822 · PMCID PMC11819481

What about cycle syncing?

Training and eating by phase is popular, but the evidence is weak. Across 78 studies, performance in the first days of the cycle was at most very slightly lower, and the researchers couldn't give general advice. We found no studies on eating by phase. So train on how you feel, not on a calendar.

The Effects of Menstrual Cycle Phase on Exercise Performance in Eumenorrheic Women: A Systematic Review and Meta-Analysis.

McNulty KL, Elliott-Sale KJ, Dolan E, Swinton PA, Ansdell P et al.

Sports Med 2020 · PMID 32661839 · PMCID PMC7497427

Current evidence shows no influence of women's menstrual cycle phase on acute strength performance or adaptations to resistance exercise training.

Colenso-Semple LM, D'Souza AC, Elliott-Sale KJ, Phillips SM

Front Sports Act Living 2023 · PMID 37033884 · PMCID PMC10076834

Part 2

Measuring

What a wearable shows

A wearable picks up your cycle in your data. Your skin temperature is about 0.3 °C higher after ovulation. Your resting heart rate swings by 2.7 beats on average, peaking just before your period. Your HRV is lower in the second half. So compare your data with the same phase of an earlier cycle.

Careful. A wearable doesn't reliably predict ovulation, doesn't diagnose anything and isn't contraception.

Two of these studies were co-run by the manufacturer (Oura, WHOOP)

A Systematic Review and Meta-Analysis of Within-Person Changes in Cardiac Vagal Activity across the Menstrual Cycle: Implications for Female Health and Future Studies.

Schmalenberger KM, Eisenlohr-Moul TA, Würth L, Schneider E, Thayer JF et al.

J Clin Med 2019 · PMID 31726666 · PMCID PMC6912442

A Novel method for quantifying fluctuations in wearable derived daily cardiovascular parameters across the menstrual cycle.

Jasinski SR, Presby DM, Grosicki GJ, Capodilupo ER, Lee VH

NPJ Digit Med 2024 · PMID 39715818 · PMCID PMC11666598

Nocturnal finger skin temperature in menstrual cycle tracking: ambulatory pilot study using a wearable Oura ring.

Maijala A, Kinnunen H, Koskimäki H, Jämsä T, Kangas M

BMC Womens Health 2019 · PMID 31783840 · PMCID PMC6883568

Which blood tests, on which day

Hormones fluctuate, so timing matters. One test says little: progesterone can even swing a lot within hours. Always note your cycle day.

FSH, LH and oestradiol

On day 2 to 6 of your cycle.

Progesterone

About 7 days before your next period. Repeat it if it's low.

TSH and prolactin

Any day. Especially with irregular or missing periods.

Testosterone and SHBG

With acne, extra hair growth or an irregular cycle.

Haemoglobin and ferritin

With heavy bleeding or tiredness.

Careful. On the pill? Then these days don't apply: the pill stops ovulation, raises SHBG and lowers your free testosterone.

bpac: testing reproductive hormones

Which day for which test

The effect of combined oral contraception on testosterone levels in healthy women: a systematic review and meta-analysis.

Zimmerman Y, Eijkemans MJ, Coelingh Bennink HJ, Blankenstein MA, Fauser BC

Hum Reprod Update 2014 · PMID 24082040 · PMCID PMC3845679

Neuroendocrine regulation of the corpus luteum in the human. Evidence for pulsatile progesterone secretion.

Filicori M, Butler JP, Crowley WF Jr

J Clin Invest 1984 · PMID 6427277 · PMCID PMC437074

Part 3

The most common problems

PMS and PMDD

Symptoms in the 1 to 2 weeks before your period that disappear once it starts, such as irritability, low mood, sore breasts and bloating. PMDD is the severe, mood-led form: confirmed in 3.2% of women. A diary over 2 to 3 cycles tells you more here than a blood test.

See your GP if daily life suffers, if symptoms continue after your period, or with dark thoughts.

The prevalence of premenstrual dysphoric disorder: Systematic review and meta-analysis.

Reilly TJ, Patel S, Unachukwu IC, Knox CL, Wilson CA et al.

J Affect Disord 2024 · PMID 38199397

Thuisarts: premenstrual syndrome

Patient information

Looks hormonal, but isn't always

Symptoms that flare around your period aren't always PMS. Often it's something you already have that gets worse in the days before your period. Your hormone levels are usually normal: the ordinary monthly shift changes a lot in your body, including parts of your immune system. Defences in the cervix and vagina drop in the second half of your cycle, and your inflammation marker (CRP) peaks during your period. In your blood, there are actually more white blood cells in the second half.

Asthma

17% of women with asthma notice it worsening around their period.

Migraine

22% of women with migraine get an attack with at least half of their periods.

Eczema

47% had monthly worsening, mostly in the week before their period.

Acne

44% noticed flares before their period.

Low mood

64% of women with depression noticed it worsening before their period.

How to tell the difference. Track how you feel every day for 2 to 3 cycles. If the week after your period is symptom-free, that fits PMS. If symptoms are there all month and only worse before your period, an existing condition is getting worse.

Towards a consensus on diagnostic criteria, measurement and trial design of the premenstrual disorders: the ISPMD Montreal consensus.

O'Brien PM, Bäckström T, Brown C, Dennerstein L, Endicott J et al.

Arch Womens Ment Health 2011 · PMID 21225438 · PMCID PMC4134928

Changes in concentrations of cervicovaginal immune mediators across the menstrual cycle: a systematic review and meta-analysis of individual patient data.

Hughes SM, Levy CN, Katz R, Lokken EM, Anahtar MN et al.

BMC Med 2022 · PMID 36195867 · PMCID PMC9533580

Endogenous reproductive hormones and C-reactive protein across the menstrual cycle: the BioCycle Study.

Gaskins AJ, Wilchesky M, Mumford SL, Whitcomb BW, Browne RW et al.

Am J Epidemiol 2012 · PMID 22306563 · PMCID PMC3282877

The effects of menstrual cycle phases on immune function and inflammation at rest and after acute exercise: A systematic review and meta-analysis.

Notbohm HL, Moser F, Goh J, Feuerbacher JF, Bloch W et al.

Acta Physiol (Oxf) 2023 · PMID 37309068

Characteristics of perimenstrual asthma and its relation to asthma severity and control: data from the Severe Asthma Research Program.

Rao CK, Moore CG, Bleecker E, Busse WW, Calhoun W et al.

Chest 2013 · PMID 23632943 · PMCID PMC3747720

Prevalence of menstrual migraine: a population-based study.

Vetvik KG, Macgregor EA, Lundqvist C, Russell MB

Cephalalgia 2014 · PMID 24101732

Premenstrual deterioration of skin symptoms in female patients with atopic dermatitis.

Kiriyama K, Sugiura H, Uehara M

Dermatology 2003 · PMID 12592076

The effect of the menstrual cycle on acne.

Stoll S, Shalita AR, Webster GF, Kaplan R, Danesh S et al.

J Am Acad Dermatol 2001 · PMID 11712049

Self-reported premenstrual exacerbation of depressive symptoms in patients seeking treatment for major depression.

Kornstein SG, Harvey AT, Rush AJ, Wisniewski SR, Trivedi MH et al.

Psychol Med 2005 · PMID 15918345

Painful periods and endometriosis

Over 7 in 10 young women have period pain. About 1 in 10 has endometriosis: tissue similar to the womb lining, outside the womb. In the Netherlands, diagnosis takes 7 years on average. No blood test helps: it comes down to your story, an examination and an ultrasound.

See your GP if painkillers or the pill don't help, with pain outside your period, or pain during sex or on the toilet.

The Prevalence and Academic Impact of Dysmenorrhea in 21,573 Young Women: A Systematic Review and Meta-Analysis.

Armour M, Parry K, Manohar N, Holmes K, Ferfolja T et al.

J Womens Health (Larchmt) 2019 · PMID 31170024

Diagnostic delay in endometriosis: is there any progress?

de Kok L, Boersen Z, Coppus S, van Haaps A, van Hanegem N et al.

Reprod Biomed Online 2026 · PMID 42054959

ESHRE guideline: endometriosis.

Becker CM, Bokor A, Heikinheimo O, Horne A, Jansen F et al.

Hum Reprod Open 2022 · PMID 35350465 · PMCID PMC8951218

Heavy bleeding and iron deficiency

Over 1 in 4 women has heavy bleeding, and almost half never saw a doctor about it. This drains your iron stores: about 4 in 10 women have iron deficiency without anaemia. Have haemoglobin and ferritin tested. Labs do use different cut-offs.

Prevalence of heavy menstrual bleeding and experiences of affected women in a European patient survey.

Fraser IS, Mansour D, Breymann C, Hoffman C, Mezzacasa A et al.

Int J Gynaecol Obstet 2015 · PMID 25627706

Iron Deficiency in Adults: A Review.

Auerbach M, DeLoughery TG, Tirnauer JS

JAMA 2025 · PMID 40159291

Dutch GP guideline: anaemia

Ferritin and cut-offs

Irregular or missing periods

In women referred for this, PCOS was by far the most common cause (82%), followed by high prolactin (7%). Under-eating with lots of training also plays a role: it occurs in almost half of female athletes. A thyroid problem mainly disturbs the cycle when it's severe. Read more about PCOS on my PCOS page.

See your GP if you haven't had a period for months, if you want to conceive, or with a stress fracture. A pregnancy test always comes first.

Prevalence of endocrine disorders in 304 premenopausal women referred with oligomenorrhoea.

Yilmaz H, Demirpence M, Belet U, Ozkiliç I, Colak A et al.

Endokrynol Pol 2024 · PMID 38497394

Low Energy Availability and Relative Energy Deficiency in Sport: A Systematic Review and Meta-analysis.

Gallant TL, Ong LF, Wong L, Sparks M, Wilson E et al.

Sports Med 2025 · PMID 39485653

Dutch GP guideline: amenorrhoea

Which tests when

Low progesterone

A short second half of the cycle occurs in about 9% of ovulatory cycles, but recurs in only 3.4% of women. According to a 2026 American guideline, it hasn't been shown to cause infertility or miscarriage, and the diagnosis is disputed.

Luteal phase deficiency in regularly menstruating women: prevalence and overlap in identification based on clinical and biochemical diagnostic criteria.

Schliep KC, Mumford SL, Hammoud AO, Stanford JB, Kissell KA et al.

J Clin Endocrinol Metab 2014 · PMID 24606080 · PMCID PMC4037737

Diagnosis and treatment of luteal phase deficiency: a Committee Opinion.

Practice Committee of the American Society for Reproductive Medicine and Practice Committee of the Society for Reproductive Endocrinology and Infertility

Fertil Steril 2026 · PMID 42414147

Perimenopause

The years before your last period, usually from your forties. Your cycle changes and you may get hot flushes, night sweats, poorer sleep and low mood. Hormone tests help little here: FSH, LH and oestradiol fluctuate too much to diagnose it.

Dutch GP guideline: menopause

Diagnosis and tests

Perimenopause: From Research to Practice.

Santoro N

J Womens Health (Larchmt) 2016 · PMID 26653408 · PMCID PMC4834516

Part 4

My story

I thought it was my hormones

My symptoms kept coming back with my cycle, acne being the clearest. So naturally I thought of my hormones. After testing, my SHBG turned out slightly low - not by much, but it seemed to fit.

Everything I tried

Before I found the cause, I had everything tested. About €10,000 in total - and nobody could help me.

Hospital visits, to rule everything out
Blood tests and DNA tests
A DUTCH test (hormones in urine) and an OAT test (organic acids in urine)
An HTMA (minerals in hair)
Two GI tests (stool)
Several clinics, also in the US

What it turned out to be

My acne didn't come from my hormones - eggs turned out to be a trigger for me. On top of that, I wasn't digesting my food well. I wasn't getting enough fluid, so my body made too little stomach acid. That switched on my immune system, and the GI tests showed a leaky gut. Because of that, my body also struggled to clear hormones. That's why fibre matters so much to me: it helps carry hormones out in your stool, so your body doesn't take them back up. Enough fibre, not as much as possible - see the part on clearance above.

My story, not advice. Your cause may be completely different. Get tested first and talk to a doctor.

Estrogen excretion patterns and plasma levels in vegetarian and omnivorous women.

Goldin BR, Adlercreutz H, Gorbach SL, Warram JH, Dwyer JT et al.

N Engl J Med 1982 · PMID 7144835

Estrogen-gut microbiome axis: Physiological and clinical implications.

Baker JM, Al-Nakkash L, Herbst-Kralovetz MM

Maturitas 2017 · PMID 28778332

Part 5

Supplements

My story shows why I never just start supplements: what looks like a hormone problem can have a completely different cause. A supplement for the wrong cause doesn't help, and can make symptoms worse or blur your test results.

What's sold for cycle symptoms

Supplements are promoted for almost every problem above. The evidence is usually small or low quality, and study doses are often above the safe limit.

Magnesium

Small studies, too little evidence. Study doses are often above the safe limit.

Vitamin B6

Low-quality studies. Too much B6 can damage nerves, and study doses are up to 5 times the Dutch maximum.

Calcium

One large study. Blocks iron uptake if you take them together.

Chasteberry (vitex)

The most studied, but many studies have a high risk of bias. Can mask high prolactin. Not in pregnancy, breastfeeding or IVF.

Omega-3 and ginger

On average favourable studies for period pain, with a high risk of bias. Delaying a check for endometriosis is the biggest risk.

Myo-inositol

Limited and uncertain evidence in PCOS. See my PCOS page.

Effect of nutritional interventions on the psychological symptoms of premenstrual syndrome in women of reproductive age: a systematic review of randomized controlled trials.

Robinson J, Ferreira A, Iacovou M, Kellow NJ

Nutr Rev 2025 · PMID 38684926 · PMCID PMC11723155

Efficacy of vitamin B-6 in the treatment of premenstrual syndrome: systematic review.

Wyatt KM, Dimmock PW, Jones PW, Shaughn O'Brien PM

BMJ 1999 · PMID 10334745 · PMCID PMC27878

Calcium carbonate and the premenstrual syndrome: effects on premenstrual and menstrual symptoms. Premenstrual Syndrome Study Group.

Thys-Jacobs S, Starkey P, Bernstein D, Tian J

Am J Obstet Gynecol 1998 · PMID 9731851

Vitex agnus-castus in premenstrual syndrome: A meta-analysis of double-blind randomised controlled trials.

Csupor D, Lantos T, Hegyi P, Benkő R, Viola R et al.

Complement Ther Med 2019 · PMID 31780016

Omega-3 long chain polyunsaturated fatty acids as a potential treatment for reducing dysmenorrhoea pain: Systematic literature review and meta-analysis.

Snipe RMJ, Brelis B, Kappas C, Young JK, Eishold L et al.

Nutr Diet 2024 · PMID 37545015

Ginger for Pain Management in Primary Dysmenorrhea: A Systematic Review and Meta-Analysis.

Moshfeghinia R, Salmanpour N, Ghoshouni H, Gharedaghi H, Zare R et al.

J Integr Complement Med 2024 · PMID 38770631

Inositol for Polycystic Ovary Syndrome: A Systematic Review and Meta-analysis to Inform the 2023 Update of the International Evidence-based PCOS Guidelines.

Fitz V, Graca S, Mahalingaiah S, Liu J, Lai L et al.

J Clin Endocrinol Metab 2024 · PMID 38163998 · PMCID PMC11099481

What's sold as 'hormone detox'

Online you'll read a lot about 'flushing out' hormones with supplements or cleanses. Your liver, bile and gut already do that work every day, and research on extra help is thin.

Detox programmes

No randomised trials of commercial detox programmes have been done in humans.

Liver flush

The 'stones' passed after such a flush turned out to be soap, formed in the gut.

Fibre

The best studied, but through ordinary food. More isn't always better.

Detox diets for toxin elimination and weight management: a critical review of the evidence.

Klein AV, Kiat H

J Hum Nutr Diet 2015 · PMID 25522674

Could these be gallstones?

Sies CW, Brooker J

Lancet 2005 · PMID 15836886

High-fiber diet reduces serum estrogen concentrations in premenopausal women.

Rose DP, Goldman M, Connolly JM, Strong LE

Am J Clin Nutr 1991 · PMID 1652197

Effect of daily fiber intake on reproductive function: the BioCycle Study.

Gaskins AJ, Mumford SL, Zhang C, Wactawski-Wende J, Hovey KM et al.

Am J Clin Nutr 2009 · PMID 19692496 · PMCID PMC2744625

Only for a measured deficiency

Some supplements only make sense if your level is actually low. Without a test you don't know, and too much can do harm.

Iron

Only useful with low ferritin. Too much iron is harmful and can hide the cause of blood loss.

Vitamin D

Low-quality studies, often with doses above the safe limit. Get your level tested first.

Never start without data. Test your markers first and talk to a doctor, especially if you take medication or the pill, want to conceive or are doing IVF.

Effect of iron supplementation on fatigue in nonanemic menstruating women with low ferritin: a randomized controlled trial.

Vaucher P, Druais PL, Waldvogel S, Favrat B

CMAJ 2012 · PMID 22777991 · PMCID PMC3414597

Efficacy of Vitamin D Supplementation to Alleviate Premenstrual Syndrome Symptoms: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

Zainab A, Tageldin RS, Patel R, Hassan MA, Aburas LA et al.

J Clin Med 2026 · PMID 42355996 · PMCID PMC13301900

The trial

Try the Cellular Trial