Hormones 101 support

Hormones are your body's chemical messengers. Small signals with wide reach. They shape your energy, sleep, mood, skin, cycle, and much more.

For women, the picture becomes more layered in perimenopause, the transitional years that often begin in the late 30s or 40s, when these messengers start to shift in new and sometimes unpredictable ways. Knowing what they are and what they do makes those changes easier to understand [1, 5]. This guide covers six areas:

– Pt.1 The Core Reproductive Hormones
– Pt.2 The Conductors of the Cycle
– Pt.3 The Stress & Energy Hormones
– Pt.4 The Thyroid Family
– Pt.5 The Mood & Wellbeing Messengers
– Pt.6 Key terms to know


Part 1: The Core Reproductive Hormones

These are the hormones most people have heard of. They drive the menstrual cycle, support fertility, and are behind many of the changes women experience during perimenopause and menopause.

Estrogen
Estrogen is not one hormone but a family of three, each prominent at a different stage of life [8, 9].

  • Estradiol (E2) is the dominant form during the reproductive years. Made mainly by the ovaries, it affects bone density, skin, brain function, and the cardiovascular system.
  • Estrone (E1) takes over after menopause, produced mainly by fat tissue using other hormones as raw material.
  • Estriol (E3) is a pregnancy hormone, produced by the placenta. Levels rise significantly during pregnancy and fall again after birth.

Estrogen's reach is wide. It touches bones, skin, heart, brain, bladder, and vaginal tissue, which is why its decline in menopause can show up in so many different ways [8, 9, 10]. After menopause, ovarian estrogen production falls substantially, though it does not reach zero. Studies of healthy postmenopausal women consistently show measurable levels of estradiol and estrone in circulation [5, 6, 8].

Progesterone
Progesterone is the cycle's second-half hormone. After ovulation, the follicle that released the egg transforms into something called the corpus luteum, which produces progesterone. It thickens the uterine lining in case a fertilised egg arrives, supports sleep, and helps keep mood steady [9, 10].

If pregnancy does not happen, the corpus luteum breaks down, progesterone drops, and a period follows. In early perimenopause, ovulation becomes less consistent, so this source of progesterone becomes less consistent too. That drop, while estrogen continues to fluctuate, can contribute to heavier periods, disrupted sleep, bloating, and mood shifts [1, 6]. 

Testosterone
Women produce testosterone in the ovaries, adrenal glands, and other tissues. Levels are lower than in men, but testosterone still matters. It contributes to sexual desire, energy, muscle strength, bone health, and general wellbeing [11, 12].

Levels start declining from the 30s, not at menopause. This is a gradual, age-related shift. Some women notice it as a change in libido, motivation, or how they feel in their body [12, 13]. Some medications affect testosterone too. Certain acne treatments, including some hormonal contraceptives and isotretinoin, can lower circulating androgens. Hair-loss medications like finasteride reduce DHT, the hormone the body makes from testosterone, with a smaller effect on testosterone itself [14].

Research from multiple clinical trials supports a role for testosterone in improving sexual desire, arousal, and satisfaction in peri- and postmenopausal women, particularly those experiencing low sexual desire alongside personal distress [12, 13].

DHEA (Dehydroepiandrosterone)
DHEA is made by the adrenal glands and acts as a building block. The body converts it into estrogen and testosterone as needed. Levels are highest in the 20s and fall steadily from there. After menopause, when the ovaries produce much less, DHEA becomes a more important source of those hormones [15, 16, 17, 18]. Vaginal DHEA (also called prasterone) has been studied as a local treatment for vaginal dryness and pain during sex, symptoms that often appear after menopause as hormone levels fall [15, 16].

 

Part 2: The Conductors of the Cycle

These hormones come from the brain and coordinate the conversation with the ovaries.

FSH (Follicle-Stimulating Hormone)
FSH is made by the pituitary gland, a pea-sized endocrine organ at the base of the brain, and prompts ovarian follicles to mature. As ovarian reserve and responsiveness decline with age, FSH often rises. The brain has to send stronger signals to get a response from the ovaries. FSH levels can fluctuate noticeably during perimenopause [6, 20].

LH (Luteinizing Hormone)
LH triggers ovulation mid-cycle. Levels may also rise during reproductive ageing as ovarian feedback shifts [20].

GnRH (Gonadotropin-Releasing Hormone)
GnRH is released by the hypothalamus, a small almond-sized structure deep within the brain that acts as the body's control centre. It tells the pituitary gland to release FSH and LH, keeping the reproductive hormone system in sync [20].

AMH (Anti-Müllerian Hormone) 
AMH reflects ovarian reserve and declines with age. AMH testing offers information about reproductive ageing, but it cannot predict fertility or the exact timing of menopause for any one woman [19].

 

Part 3: The Stress and Energy Hormones

These hormones interact closely with the reproductive system and shape sleep, metabolism, and stress in midlife.

Cortisol
The body's main stress hormone, produced by the adrenal glands, small triangular-shaped endocrine glands on top of the kidneys. Cortisol follows a daily rhythm: higher in the morning, lower at night. It helps regulate metabolism, blood sugar, immune function, and inflammation. Hormonal shifts during perimenopause may change stress sensitivity, sleep quality, and mood [21].

Adrenaline and Noradrenaline
These fast-acting hormones shape the body's stress response and temperature regulation. Changes in norepinephrine signalling are thought to play a role in hot flashes and night sweats [7, 23].

Insulin 
Insulin moves glucose from the blood into cells. During and after menopause, changes in estrogen, body composition, and age can lower insulin sensitivity and raise the risk of central weight gain and type 2 diabetes [22].

 

Part 4: The Thyroid Family

Thyroid hormones regulate metabolism, body temperature, energy use, mood, and many other functions. Thyroid disorders are common in women and often overlap with perimenopausal symptoms [24, 25].

TSH (Thyroid-Stimulating Hormone)
TSH is produced by the pituitary gland and tells the thyroid to make thyroid hormones. It is the most common screening test for thyroid function [24, 26].

T4 (Thyroxine) and T3 (Triiodothyronine)
T4 is the main hormone released by the thyroid. It works largely as a precursor to T3, the more biologically active form. Low thyroid hormone levels can contribute to fatigue, weight gain, cold intolerance, hair thinning, constipation, and low mood [25, 26, 27]. 

 

Part 5: The Mood and Wellbeing Messengers

These brain chemicals work alongside the endocrine system and shape mood, motivation, sleep, and emotional life.

Serotonin 
A neurotransmitter involved in mood, appetite, and sleep. Estrogen interacts with serotonin pathways, so hormonal shifts during perimenopause may affect mood for some women [29]. Medications that strongly affect serotonin signalling, including SSRIs and SNRIs, are associated with sexual side effects in some people, including reduced desire and difficulty with arousal or orgasm. 

Dopamine
Dopamine shapes motivation, reward, pleasure, and goal-directed behaviour. Estrogen and testosterone both influence dopamine signalling, which can affect energy, libido, and motivation during hormonal transitions [29].

Melatonin
Melatonin is made by the pineal gland and helps regulate sleep and circadian rhythms. Production declines with age. Sleep disruption during perimenopause is also shaped by night sweats and hormonal fluctuations [28].

Oxytocin
Oxytocin is involved in childbirth, breastfeeding, social bonding, and emotional connection. It also plays a role in stress regulation and social behaviour.

 

Part 6: Key Terms

Perimenopause
The transitional years before menopause, when hormone levels fluctuate and cycles become less predictable. Perimenopause often begins in the 40s, though some women notice changes in their late 30s. It can last several years [1, 2, 3, 6]. Read more: The stages of menopause

Menopause
Menopause is defined as 12 consecutive months without a menstrual period. The average age of menopause in the United States is around 51 [4, 5].

Postmenopause
The years after menopause. Hormone levels generally settle at lower levels than during the reproductive years [5].

Relative Estrogen–Progesterone Imbalance
In early perimenopause, ovulation can become less consistent. Progesterone exposure drops while estrogen continues to fluctuate. This pattern may contribute to heavier bleeding, breast tenderness, bloating, and mood changes [1, 6].

HPA Axis
The hypothalamic-pituitary-adrenal (HPA) axis regulates the stress response and works closely with the reproductive hormone system.

Endocrine System
The network of glands and organs that produce hormones, including the ovaries, adrenal glands, thyroid, pituitary gland, and pancreas. These systems communicate through hormonal feedback loops that regulate metabolism, reproduction, stress, sleep, and more.

 

In short

Hormones work as a system, not in isolation. The reproductive hormones, estrogen, progesterone, testosterone, and DHEA, are central to the changes women experience in perimenopause and beyond, but they interact with brain signals, stress hormones, thyroid function, and neurotransmitters. Understanding each one separately is a starting point. Understanding how they connect is where the picture becomes clearer.

 

FAQ

What is the difference between perimenopause and menopause? Perimenopause is the transitional phase when hormone levels begin to shift and cycles become irregular. Menopause is the point when a woman has gone 12 consecutive months without a period. Perimenopause can last several years before that point is reached [1, 4].

Why does progesterone decline before estrogen in perimenopause? In early perimenopause, ovulation becomes less consistent. Because progesterone is produced after ovulation by the corpus luteum, less frequent ovulation means less progesterone. Estrogen, produced by the ovaries throughout the cycle, continues to fluctuate. This means the two hormones can fall out of their usual relationship before overall estrogen levels drop significantly [1, 6].

Does estrogen disappear after menopause? No. Ovarian estrogen production falls substantially after menopause, but circulating estrogen does not reach zero. Estrone, produced through conversion of adrenal hormones in fat tissue, remains the predominant form and is measurable in healthy postmenopausal women [5, 8].

Can thyroid symptoms be confused with perimenopausal symptoms? Yes. Fatigue, weight changes, mood shifts, and sleep disruption can appear in both thyroid disorders and perimenopause. Thyroid disorders are more common in women, and the conditions can occur simultaneously. A blood test measuring TSH is the standard first step to assess thyroid function [24, 25].

What is the HPA axis and why does it matter in midlife? The hypothalamic-pituitary-adrenal (HPA) axis governs the body's stress response. It works in close communication with the reproductive hormone system, which is why chronic stress can affect the menstrual cycle, and why hormonal shifts in perimenopause can change how the body handles stress [21].

 

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While this Hormone 101 Support is carefully written and references peer-reviewed sources. It is for informational purposes only and is not medical advice.

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References

Perimenopause and Menopause

  • [1] Harvard Health Publishing — Perimenopause: Rocky Road to Menopause. https://www.health.harvard.edu/womens-health/perimenopause-rocky-road-to-menopause
  • [2] Cleveland Clinic — Perimenopause. https://my.clevelandclinic.org/health/diseases/21608-perimenopause
  • [3] Mayo Clinic — Perimenopause. https://www.mayoclinic.org/diseases-conditions/perimenopause/symptoms-causes/syc-20354666
  • [4] Mayo Clinic — Menopause. https://www.mayoclinic.org/diseases-conditions/menopause/symptoms-causes/syc-20353397
  • [5] National Institute on Aging — Menopause. https://www.nia.nih.gov/health/menopause
  • [6] The Menopause Society — Perimenopause. https://menopause.org/patient-education/menopause-topics/perimenopause
  • [7] The Menopause Society — Hot Flashes. https://menopause.org/patient-education/menopause-topics/hot-flashes 

Estrogen and Reproductive Hormones

  • [8] Cleveland Clinic — Estrogen. https://my.clevelandclinic.org/health/body/22398-estrogen
  • [9] StatPearls — Physiology, Estrogen. https://www.ncbi.nlm.nih.gov/books/NBK538260/
  • [10] Merck Manual — Female Reproductive Endocrinology. https://www.merckmanuals.com/
  • [11] Cleveland Clinic — Testosterone. https://my.clevelandclinic.org/health/body/24897-testosterone
  • [12] Endocrine Society Clinical Practice Guideline — Androgen Therapy in Women. https://academic.oup.com/jcem/article/99/10/3489/2539261
  • [13] The Menopause Society — Testosterone Use for Hypoactive Sexual Desire Disorder. https://menopause.org/patient-education/menopause-topics/testosterone-use-for-hypoactive-sexual-desire-disorder
  • [14] Mayo Clinic — Low Sex Drive in Women. https://www.mayoclinic.org/healthy-lifestyle/womens-health/expert-answers/low-sex-drive-in-women/faq-20058237
  • [15] Cleveland Clinic — DHEA. https://my.clevelandclinic.org/health/body/24558-dhea
  • [16] Mount Sinai — DHEA Supplement Information. https://www.mountsinai.org/health-library/supplement/dehydroepiandrosterone
  • [17] Endocrine Society — Adrenal Fatigue. https://www.endocrine.org/patient-engagement/endocrine-library/adrenal-fatigue
  • [18] Merck Manual — Overview of the Adrenal Glands. https://www.merckmanuals.com/home/hormonal-and-metabolic-disorders/adrenal-gland-disorders/overview-of-the-adrenal-glands 

Cycle Hormones and Ovarian Reserve

  • [19] Cleveland Clinic — Anti-Müllerian Hormone Test. https://my.clevelandclinic.org/health/diagnostics/22681-anti-mullerian-hormone-test
  • [20] StatPearls — Physiology of FSH, LH, and GnRH. https://www.ncbi.nlm.nih.gov/books/NBK535442/

Stress Hormones and Metabolism

  • [21] Cleveland Clinic — Cortisol. https://my.clevelandclinic.org/health/articles/22187-cortisol
  • [22] Mayo Clinic — Menopause Weight Gain. https://www.mayoclinic.org/diseases-conditions/menopause/in-depth/menopause-weight-gain/art-20046058
  • [23] StatPearls — Hot Flashes and Menopause Physiology. https://www.ncbi.nlm.nih.gov/books/NBK507826/ 

Thyroid Health

  • [24] American Thyroid Association — Thyroid Function Tests. https://www.thyroid.org/thyroid-function-tests/
  • [25] Mayo Clinic — Hypothyroidism. https://www.mayoclinic.org/diseases-conditions/hypothyroidism/symptoms-causes/syc-20350284
  • [26] Cleveland Clinic — Thyroid Hormones. https://my.clevelandclinic.org/health/body/23188-thyroid-hormones
  • [27] NIDDK — Hypothyroidism (Underactive Thyroid). https://www.niddk.nih.gov/health-information/endocrine-diseases/hypothyroidism-underactive-thyroid

Neurotransmitters, Mood, and Sleep

  • [28] Cleveland Clinic — Melatonin. https://my.clevelandclinic.org/health/articles/23411-melatonin
  • [29] Harvard Health Publishing — Perimenopause and Mood. https://www.health.harvard.edu/womens-health/perimenopause-rocky-road-to-menopause
  • [30] NCBI Bookshelf — Neuroendocrinology Resources. https://www.ncbi.nlm.nih.gov/books/