Estrogen gets almost all the attention in conversations about menopause — and it deserves attention, because its role is substantial and its decline is consequential. But estrogen is one of four hormones whose significant changes during this transition collectively explain the full picture of what’s happening in the body after 40. Understanding each hormone — what it does, how it changes, and what those changes mean — transforms the experience from a confusing collection of symptoms into a coherent physiological story.
The four hormones most significantly involved in the menopause transition are estrogen, progesterone, testosterone, and FSH (follicle-stimulating hormone). Each plays distinct roles. Each changes in distinct ways. And the changes don’t happen in isolation — they interact with each other and with every other hormone system in the body in ways that produce the complex, often unpredictable symptom picture most women experience.
Estrogen: The Hormone Everyone Knows About
Estrogen is not a single hormone but a family of related hormones, the most significant of which are estradiol (E2), estrone (E1), and estriol (E3). During reproductive years, estradiol is the dominant form and the most potent — produced primarily by the ovaries in response to FSH and LH signaling. After menopause, estrone becomes the dominant form, produced primarily through the conversion of androgens in fat tissue and the adrenal glands.
What estrogen does in the body is remarkably extensive — which explains why its decline affects so many systems simultaneously. Estrogen regulates the menstrual cycle, supports bone density by inhibiting osteoclast activity, protects cardiovascular health by maintaining arterial flexibility and favorable lipid profiles, influences brain function including memory, mood, and cognitive speed, regulates body temperature through the hypothalamus, maintains the health of vaginal and urinary tract tissue, supports skin collagen production, and influences insulin sensitivity in every major tissue type.
This breadth is why the decline of estrogen during perimenopause and menopause produces effects across so many body systems simultaneously. Hot flashes are the hypothalamus responding to estrogen fluctuation. Sleep disruption is partially the brain responding to changing estrogen and progesterone levels. Bone density loss is the skeleton responding to the loss of estrogen’s protective inhibition of bone resorption. Brain fog and memory changes are the brain adjusting to a lower-estrogen environment. These are not separate problems — they’re different expressions of the same underlying hormonal change.
The pattern of estrogen decline during perimenopause is important to understand because it’s not linear. Estrogen doesn’t simply decrease steadily from year to year. Instead it fluctuates dramatically — sometimes producing more estrogen in a given cycle than the body produced in years, then dropping sharply. This fluctuation — not simply low estrogen — is what drives many of the most acute perimenopausal symptoms. The hypothalamus, accustomed to estrogen operating within a predictable range, is responding to signals it doesn’t recognize.
Progesterone: The Hormone That Declines First
While estrogen gets most of the attention, progesterone actually begins its significant decline earlier in the perimenopause transition — and its early decline explains several of the symptoms that women notice first but may not attribute to hormonal change.
Progesterone is produced primarily by the corpus luteum — the structure that forms after ovulation from the follicle that released the egg. As the ovarian reserve declines in early perimenopause, ovulation becomes less consistent, and cycles where ovulation doesn’t occur (anovulatory cycles) become more frequent. Without ovulation there is no corpus luteum and therefore no progesterone production in the second half of the cycle. The result is a relative progesterone deficiency that can develop years before estrogen levels become significantly affected.
Progesterone’s functions explain why its early decline produces the symptom pattern that characterizes early perimenopause. Progesterone has a calming effect on the nervous system through its support of GABA — the brain’s primary inhibitory neurotransmitter — and its metabolism to allopregnanolone, a potent GABA-A receptor modulator. When progesterone declines, this calming influence diminishes, which explains the heightened anxiety, sleep disruption, and mood variability that often precede other perimenopausal symptoms.
Progesterone also opposes estrogen’s stimulating effects on the uterine lining. When progesterone is insufficient relative to estrogen — a state sometimes called estrogen dominance — the uterine lining may not shed completely or may overgrow, producing heavier, longer, or more irregular periods. This is one of the mechanisms behind the heavy bleeding that affects many women in early to mid perimenopause.
A 2018 study published in Fertility and Sterility found that anovulatory cycles increased significantly in the early perimenopause years, preceding the estrogen fluctuations that most women and clinicians associate with the transition. Progesterone’s story is earlier and often unrecognized.
Testosterone: The Overlooked Hormone
Testosterone in women is produced by the ovaries and the adrenal glands. It exists at much lower concentrations than in men but plays significant roles in female physiology — roles that often become apparent only when its levels decline.
Testosterone contributes to libido and sexual arousal, supporting both the desire for sexual activity and the physical arousal response. It supports muscle maintenance and bone density alongside estrogen. It influences energy levels, motivation, and the capacity for assertiveness and confidence that many women describe as part of their sense of self. And it plays a role in cognitive function, particularly in areas related to focus, drive, and mental energy.
Testosterone levels in women peak in the twenties and decline gradually throughout adulthood, with a more significant decline occurring around menopause as ovarian production decreases. Some women notice this decline as reduced libido, decreased motivation, reduced energy for activities that previously felt energizing, and a subtle but real sense of decreased drive or assertiveness.
The testosterone story in women’s health is complicated by the fact that testosterone testing in women is less standardized than in men, and the “normal” ranges used in most laboratory settings are developed primarily from male populations. Women can have clinically significant testosterone deficiency by the standards of female physiology while testing within “normal” ranges by laboratory reference values. Clinical assessment — based on symptoms alongside testing — is essential.
Testosterone therapy for women remains an area of active research and genuine clinical utility, though it’s less commonly discussed than estrogen therapy and less consistently offered. For women experiencing significant libido changes, persistent fatigue that doesn’t respond to other interventions, or declining motivation and drive, a conversation with a menopause specialist about testosterone evaluation is warranted.
FSH: The Messenger That Tells the Story
FSH — follicle-stimulating hormone — is produced by the pituitary gland and signals the ovaries to develop follicles and produce estrogen. When the ovaries’ capacity to respond to FSH declines during perimenopause, the pituitary responds by producing more FSH — essentially turning up the signal when the response weakens.
This is why FSH levels rise during perimenopause and are often used as a marker of the transition. A sustained FSH level above 25-30 IU/L typically indicates perimenopause; above 40 IU/L is associated with menopause, though FSH fluctuates significantly during perimenopause and a single measurement has limited diagnostic value. FSH doesn’t produce symptoms directly, but its rising levels are a reflection of the ovarian changes that drive everything else.
FSH elevation also explains why some women in perimenopause experience heightened ovarian activity alongside declining function — the pituitary is pushing harder, which can produce irregular bursts of estrogen production between periods of decline. This paradoxical pattern — sometimes more estrogen than before, followed by drops — is the mechanism behind the dramatic hormonal fluctuations that produce many perimenopausal symptoms.
How the Hormones Interact
The four hormones don’t change in isolation. Their interactions produce effects more complex than any single hormone’s change would suggest.
The estrogen-cortisol interaction is particularly significant. Estrogen supports the regulation of cortisol — the primary stress hormone — through its influence on the hypothalamic-pituitary-adrenal axis. As estrogen declines, cortisol regulation becomes less precise, producing the more reactive stress response that many women notice during perimenopause. The same stressor that was manageable at 35 produces a larger cortisol response at 47 — not because external circumstances have worsened, but because the hormonal buffer that moderated the stress response has diminished.
The estrogen-insulin interaction drives the metabolic changes described in the previous article — insulin sensitivity declining as estrogen declines, producing the blood sugar instability that affects energy, weight, and cravings.
The progesterone-thyroid interaction is less commonly discussed but clinically relevant. Adequate progesterone supports thyroid hormone activity and conversion of T4 to the more active T3. Progesterone decline can contribute to relative thyroid underactivity that shows up as fatigue, weight changes, and cognitive symptoms — and that can be difficult to distinguish from perimenopausal symptoms without appropriate testing.
The cortisol-estrogen feedback loop deserves additional attention because chronic stress during perimenopause creates a specifically damaging dynamic. Elevated cortisol suppresses estrogen production through the hypothalamic-pituitary axis. Lower estrogen produces a more reactive stress response. The more reactive stress response elevates cortisol further. This loop can be one of the reasons that perimenopausal symptoms worsen during periods of elevated life stress and improve somewhat when stress is reduced.
What This Means for Understanding Your Own Experience
The hormonal complexity of this transition explains why the symptom picture is so variable between women — and why generic descriptions of menopause as “hot flashes and mood swings” capture only a small fraction of what’s actually happening.
A woman whose progesterone declines significantly before estrogen fluctuation begins will have an early-perimenopause experience dominated by anxiety, sleep disruption, and mood changes — which may not be recognized as hormonal at all without appropriate context. A woman whose estrogen fluctuates dramatically will have a mid-perimenopause experience dominated by hot flashes, temperature dysregulation, and sleep disruption. A woman with significant testosterone decline will have an experience colored by libido changes, fatigue, and reduced motivation alongside whatever else is occurring.
Understanding which hormones are most significantly involved in your experience helps identify which conversations with your doctor are most relevant, which symptoms are most likely to respond to which interventions, and how to make sense of an experience that can otherwise feel random and overwhelming.
Common Questions About Hormonal Changes
Can I test my hormone levels to know where I am?
Testing can provide useful information but has real limitations during perimenopause specifically. Because hormone levels fluctuate significantly throughout each cycle and from cycle to cycle during perimenopause, a single test captures a moment in time rather than the full picture. FSH testing on days 2-3 of the cycle is most informative. Serial testing over several cycles provides more useful data than a single measurement. And clinical assessment alongside testing — your symptoms, your cycle changes, your age and health history — is always more informative than test results alone.
Do I need hormone therapy?
This is a clinical question that depends on your specific symptoms, health history, stage of the transition, and personal values and preferences. Hormone therapy is not appropriate for everyone, and it’s not necessary for everyone. But for women with significant symptoms that are affecting quality of life, it’s often the most effective intervention available and is considerably safer than was believed following the misinterpretation of the 2002 Women’s Health Initiative findings. Chapter 20 of the Menopause Reset covers the current evidence on hormone therapy in detail.
What does “estrogen dominance” mean?
“Estrogen dominance” refers to a state of relative excess estrogen compared to progesterone — not necessarily abnormally high estrogen, but estrogen that is high relative to a declining progesterone. It’s a useful concept for understanding the early perimenopause symptom pattern where progesterone has declined more significantly than estrogen. Common manifestations include heavy periods, breast tenderness, bloating, mood changes, and sleep disruption.
How do I know if my symptoms are hormonal or something else?
The most useful approach is to track symptoms alongside the menstrual cycle for at least two to three cycles. Symptoms that worsen predictably in the premenstrual phase, that improve after menstruation, or that correlate with what you know about your cycle timing are likely to have a significant hormonal component. Symptoms that are continuous and don’t vary with cycle timing are worth investigating for other causes alongside the hormonal picture. A doctor who is familiar with perimenopause can help distinguish between hormonal and non-hormonal contributors.
The DHEA-Androgen Connection
Dehydroepiandrosterone (DHEA) is a precursor hormone produced primarily by the adrenal glands that converts into both estrogen and testosterone in peripheral tissues. DHEA production peaks in the mid-twenties and declines steadily with age — more gradually than the ovarian hormone changes of perimenopause, but meaningfully enough to affect the hormonal picture by the late forties and fifties.
Declining DHEA contributes to the reduction in androgen levels, including testosterone, that accompanies menopause and that produces the libido, energy, and motivation effects described earlier. Intrarosa, a vaginal DHEA preparation, has been FDA-approved for painful intercourse associated with menopause, and systemic DHEA supplementation is being studied for its effects on multiple aspects of menopause including sexual function, energy, and muscle maintenance.
The DHEA picture is complicated enough that it warrants clinical evaluation rather than self-supplementation. Testing DHEA-S levels alongside the standard perimenopause hormone panel gives a more complete picture of the androgen situation and helps identify whether DHEA support is relevant to your individual experience.
Hormonal Contraception and Perimenopause
Many women are still using hormonal contraception during perimenopause — for both contraceptive purposes and sometimes for symptom management. The interaction between hormonal contraception and perimenopausal hormonal changes is worth understanding clearly.
Combined oral contraceptives, the contraceptive patch, and the vaginal ring all suppress the body’s own hormone production and replace it with synthetic hormones. This means that perimenopausal symptoms are often masked while using these methods — the hormonal fluctuations that cause hot flashes, mood changes, and sleep disruption are suppressed by the consistent synthetic hormone delivery. A woman on the pill may not know she’s in perimenopause because the pill is managing her hormonal environment.
This is both an advantage — symptom management — and a potential concern, because it delays the information that would otherwise be available about where she is in the transition. Transitioning from hormonal contraception to hormone therapy around menopause requires careful timing and medical guidance to avoid a hormonal gap that allows symptoms to emerge suddenly.
Progestogen-only methods, including the hormonal IUD, implant, and mini-pill, have different effects on perimenopause and may allow more of the body’s natural hormonal fluctuation to express itself while providing contraception. The hormonal IUD in particular is often used alongside systemic estrogen therapy in perimenopause, providing both contraception and the progestogen component of combined hormone therapy.