Hormones are chemical messengers. In women, two of the key hormones are estrogen and progesterone. They steer many parts of the body, like reproductive organs, bones, mood, and even the heart. Their levels rise and fall at each stage of life, from the teenage years all the way through menopause. When things get out of balance, problems show up like irregular periods, mood swings, fertility issues, menopausal symptoms, and more. In this post, we’ll explore how estrogen and progesterone work during the menstrual cycle, pregnancy, perimenopause, and menopause, and what happens when the balance shifts.
Highlights on Estrogen & Progesterone Hormones
Estrogen is a primary hormone in women. It is produced mainly by the ovaries (and in smaller amounts by other tissues). It drives the development of the uterus lining, helps egg maturation, supports bone strength, and more.
Progesterone is produced after ovulation by the corpus luteum (a temporary gland from the follicle that released the egg) and later by the placenta if pregnancy occurs. It is sometimes called the “maintenance” hormone because it helps prepare and maintain the uterus for pregnancy.
In a normal cycle, these two hormones work together. Estrogen rises first, thickening the uterine lining. After ovulation, progesterone rises, making the lining supportive for a fertilized egg. If no pregnancy happens, both hormones fall and menstruation begins.
When things go wrong, if estrogen is too high relative to progesterone, or progesterone falls too early or too low, symptoms can occur. For example, low progesterone may mean the lining isn’t well supported for pregnancy.
The Menstrual Cycle: Month by Month
Let’s walk through how estrogen and progesterone behave in a typical 28-day cycle. Of course, many women have slightly longer or shorter cycles.
Follicular phase (Day 1 to ovulation)
- Day 1 marks the start of menstruation. Both estrogen and progesterone levels are low as the uterus sheds its lining.
- As the follicle in the ovary begins to mature, estrogen rises. It stimulates thickening of the uterine lining (endometrium).
- Estrogen also affects other tissues: bone, brain, and cardiovascular system. Low estrogen affects bone density later in life.
- Near ovulation, estrogen peaks. The high level signals the pituitary to release a surge of luteinizing hormone (LH), which triggers ovulation.
Luteal phase (after ovulation until next period)
- After the egg is released, the corpus luteum produces progesterone and some estrogen. Progesterone dominates in this phase.
- Progesterone makes the lining more vascular (blood-rich) and suited for an embryo to implant.
- If fertilization doesn’t happen, progesterone and estrogen fall, and the lining sheds- you get your period.
- During this time, many women feel pre-menstrual symptoms (PMS): mood changes, breast tenderness, and cravings likely linked to hormone shifts.
Why hormone imbalances matter in the cycle
- If estrogen rises but ovulation doesn’t happen, progesterone may not rise — this tips the balance.
- If progesterone is low, the luteal phase may be shorter or the lining may not be well supported.
- Irregular cycles, heavy periods, and very light periods may signal an underlying hormone imbalance or other issue.
Pregnancy: A Whole New Hormonal Landscape
When pregnancy occurs, the body adapts. Estrogen and progesterone remain vital, but their roles and sources change.
- After fertilization, the placenta takes over hormone production from the corpus luteum. Progesterone keeps the uterus calm and the lining sustained.
- Estrogen levels soar during pregnancy. Estrogen supports uterine blood flow, placenta development, labour preparation, and fetal growth.
- One specific form, estriol, becomes very high late in pregnancy; it helps prepare the body for labour and milk production.
- If either hormone doesn’t rise appropriately, pregnancy may be challenged (e.g., implantation failure or miscarriage).
Perimenopause: The Transition Years
Perimenopause is the period leading up to menopause when the ovarian reserve declines and hormone levels start to fluctuate and drop. For many women, this begins in their 40s, though it can begin earlier or later.
During this time:
- Estrogen levels start to go down, but not smoothly. They may fluctuate widely: sometimes high, sometimes low.
- Progesterone levels drop more markedly because ovulation becomes irregular or fails to occur. If there is no ovulation, there is little progesterone produced.
- Because progesterone falls first, relative estrogen may seem higher → this “unopposed” estrogen can cause heavier or unpredictable bleeding, breast tenderness, and mood swings.
- Other symptoms become common: hot flashes, night sweats, vaginal dryness, and sleep problems. These are largely driven by changing estrogen/progesterone dynamics.
- The menstrual cycle gets irregular, and eventually the periods stop.
Understanding this stage is key. Hormone shifts here affect not just the reproductive system but also bone health, cardiovascular health, and mood. Lower estrogen is linked to faster bone loss; therefore, early perimenopause or abrupt drops can raise the risk of osteoporosis.
Menopause: The End of Monthly Cycles
Menopause is defined as 12 consecutive months with no period. It typically occurs after the age of 50. At this point, the ovaries no longer release eggs, and hormone production by the ovaries declines dramatically.
Key hormone changes:
- Estrogen production falls significantly. Without the ovarian source and with fewer follicles, estrogen levels drop.
- Progesterone levels also fall because no ovulation = no corpus luteum.
- The ratio of hormones, the fluctuations, and the feedback loops all change. Many women feel relief from monthly symptoms but begin to experience longer-term effects of low estrogen: vaginal changes, bone thinning, increased cardiovascular risk, changes in fat distribution, metabolism shifts.
- Some symptoms persist into post-menopause: hot flashes can continue for years; mood, sleep, and sexual health can be affected.
Imbalances: What Happens When Hormones Go Off Track
When the finely-tuned interplay of estrogen and progesterone is disturbed, a range of issues appear.
Polycystic Ovary Syndrome (PCOS)
One well-studied example is Polycystic Ovary Syndrome (PCOS). In PCOS:
- Ovulation is often irregular or absent. Without ovulation, progesterone doesn’t rise properly.
- Estrogen may be normal or even elevated, or the ratio (estrogen to progesterone) is skewed such that estrogen’s effects go unchecked.
- This “unopposed” estrogen can lead to heavy bleeding, irregular cycles, and endometrial thickening.
- PCOS also involves androgens and insulin resistance, so hormone imbalances extend beyond just estrogen/progesterone.
- Mood issues, fertility challenges, and metabolic risks (diabetes, cardiovascular disease) are also seen.
Mood Swings, PMS, Heavy Periods
When progesterone falls too early or is too low in a cycle, women may feel mood swings, irritability, poor sleep, fatigue- symptoms linked to PMS.
When estrogen is high without enough progesterone, the lining may build too thickly, causing heavier periods or longer cycles.
Thus, balance is as important as absolute levels.
Bone, Heart, and Other Systems
Estrogen contributes to bone health by helping regulate bone-building and breakdown. Lower estrogen (as in menopause) increases osteoporosis risk. Estrogen also influences cardiovascular health, brain health, and more.
Progesterone, too, has roles outside reproduction: it influences the nervous system, bone, and mood.
Practical Tips: Supporting Hormonal Balance
While hormones are complex and many factors (age, genetics, health, lifestyle) affect them, here are some general ideas:
- Track cycles: Understanding your own cycle helps you notice changes.
- Healthy lifestyle: Balanced diet, regular exercise, good sleep — all support hormonal health.
- Maintain a healthy weight: Especially for conditions like PCOS, body fat influences hormone conversion and metabolism.
- Manage stress: Chronic stress can affect hormone balance (e.g., cortisol, insulin), which in turn affects reproductive hormones.
- See a medical professional: If you have very irregular cycles, heavy bleeding, fertility concerns, symptom burden (hot flashes, mood swings) — consult with a gynae-endocrinologist. Some tests may help, though for some stages (like perimenopause), hormone levels fluctuate too much to rely on alone.
- Be proactive about bone and heart health: Especially as estrogen declines.
- Know your options: Hormone therapy (e.g., for menopausal symptoms) is a nuanced field. Good information and individualised care matter.
Conclusion
Estrogen and progesterone are not just “women’s hormones” that only affect the monthly period. They influence every stage of a woman’s life: from puberty, through the fertile years, pregnancy, the transition of perimenopause, and into post-menopause. The rise and fall of these hormones shape the menstrual cycle, support pregnancy, regulate mood and energy, affect bones, heart, and more.
Talking to a healthcare professional like SAAK Health early can help you navigate transitions smoothly.
Frequently Asked Questions about Estrogen, Progesterone & Hormone Balance
1. What causes estrogen and progesterone levels to fluctuate throughout a woman’s life?
Estrogen and progesterone change naturally with life stages: puberty, the monthly menstrual cycle, pregnancy, perimenopause, and menopause. Fluctuations happen because ovarian activity, ovulation frequency and the follicle (egg) reserve vary with age and health.
2. How do estrogen and progesterone imbalances affect the menstrual cycle?
If estrogen is relatively high or progesterone is too low, the uterine lining can become too thick or shed irregularly. This can cause heavy bleeding, irregular cycle length, stronger PMS, and difficulties with conception.
3. Why do hormone levels decline during perimenopause and menopause?
With age the ovarian reserve and frequency of ovulation fall. Progesterone typically drops first because it depends on ovulation; estrogen then declines more steadily. Menopause is reached after 12 consecutive months without a period, when ovarian hormone production is much lower.
4. What symptoms indicate that estrogen or progesterone may be out of balance?
Signs include irregular or heavy periods, breast tenderness, mood swings, hot flashes, sleep disruption, fatigue, changes in libido, and fertility issues. Specific symptoms vary depending on which hormone is out of balance and life stage.
5. How do estrogen and progesterone changes impact overall health beyond reproduction?
These hormones affect bone density, cardiovascular health, metabolism, brain function and mood. For example, lower estrogen after menopause increases risk of osteoporosis and can affect heart disease risk and vaginal health.