Hot flashes, night sweats, unexplained fatigue and changes in sleep are often dismissed as signs of stress or ageing. However, for some women, these changes may be connected to the hormonal transition that eventually leads to menopause.

Menopause is a natural stage of life, but the changes associated with it do not necessarily begin when periods stop. Research suggests that hormonal shifts and changes in certain health markers can develop many years before a woman's final menstrual period.

A study published in Nature Medicine, which analysed extensive laboratory data from more than one million women in the United States and Israel, has offered new insights into how the menopause transition may affect the body. The findings suggest that changes are not limited to reproductive hormones and may also be reflected in tests associated with other organs and body systems.

What Is Menopause and Why Does It Change the Body?

Menopause is the stage when a woman permanently stops menstruating because ovarian activity declines. It is generally diagnosed after 12 consecutive months without a menstrual period, provided there is no other explanation.

The transition leading up to menopause is known as perimenopause. During this phase, ovarian hormone production changes, particularly the levels of oestrogen. These fluctuations can affect menstrual cycles, temperature regulation, sleep, mood and other aspects of health.

Natural menopause most commonly occurs between the ages of 45 and 55, although the timing varies considerably.

Importantly, menopause is not a disease. However, understanding its effects can help women recognise symptoms, manage discomfort and discuss preventive healthcare with their doctors.

Five Important Changes That May Appear Before Menopause

The timing and intensity of symptoms differ from one woman to another. The following are five changes worth understanding, although none can independently predict when menopause will occur.

1. Hot Flashes and Sudden Feelings of Heat

Hot flashes are among the best-known symptoms associated with the menopause transition. A woman may suddenly feel intense warmth, particularly around the face, neck and chest, sometimes accompanied by sweating or a rapid heartbeat.

These episodes are associated with changes in the body's temperature-regulation mechanisms during hormonal fluctuations. They can occur during the day or at night.

Some women experience them years before their final period, while others have few or no hot flashes.

2. Night Sweats and Disturbed Sleep

Night sweats involve episodes of sweating during sleep that may be intense enough to dampen clothing or bedding.

Repeated episodes can interrupt sleep and leave a person feeling tired the following morning. Hormonal changes may also affect sleep through mechanisms unrelated to night sweats.

However, persistent night sweats should not automatically be attributed to menopause. Infections, certain medications, thyroid disorders and other medical conditions can produce similar symptoms.

3. Changes in Menstrual Cycles

Changes in menstrual patterns are often an important sign of perimenopause. Periods may become irregular, occur closer together or farther apart, or vary in duration and flow.

These changes happen as ovarian function becomes less predictable.

Nevertheless, irregular periods can also result from pregnancy, thyroid problems, stress, certain medications and other gynaecological conditions. Unusually heavy bleeding, bleeding between periods or any bleeding after menopause warrants medical evaluation.

4. Mood Changes, Fatigue and Difficulty Concentrating

Some women report irritability, mood fluctuations, anxiety, reduced concentration or a feeling of mental fog during the menopause transition.

Sleep disturbances and hormonal changes may contribute to these experiences. Fatigue can become more noticeable when sleep is repeatedly interrupted.

However, these symptoms are not specific to menopause. Anaemia, thyroid disorders, depression, stress and nutritional deficiencies can also cause fatigue or concentration difficulties.

If symptoms persist or interfere with daily activities, a medical assessment can help identify the cause.

5. Changes in Bone Health and Other Health Markers

One of the important findings highlighted by menopause research is that the transition may coincide with changes beyond the reproductive system.

Oestrogen plays a significant role in maintaining bone density. As oestrogen levels decline, bone loss can accelerate, increasing the risk of osteoporosis in some women.

Hormonal changes can also influence cholesterol levels and other metabolic processes. The effects vary between individuals, and not every change in a laboratory result is necessarily caused by menopause.

The study's broader findings suggest that examining health changes across multiple systems may provide a more complete understanding of the menopause transition.

What Did the Study Discover About Hormonal Changes?

Researchers analysed a very large collection of laboratory results from more than one million women in the United States and Israel. The analysis examined patterns in reproductive hormones and other laboratory measurements around the menopause transition.

Three hormones are particularly relevant:

• Anti-Müllerian hormone (AMH): This hormone is associated with the ovarian reserve, or the remaining supply of eggs. Its levels generally decline as ovarian reserve decreases.

• Follicle-stimulating hormone (FSH): Produced by the pituitary gland, FSH helps regulate ovarian function. Its levels often rise as ovarian activity declines.

• Estradiol: This is a major form of oestrogen. Its levels can fluctuate during perimenopause and generally decline as menopause approaches.

According to the reported findings, AMH levels began declining more rapidly approximately 15 years before the final menstrual period, while FSH levels increased. Estradiol showed a more pronounced decline roughly 12 years before menopause.

The researchers also identified changes in multiple laboratory measurements related to areas such as bone health, kidney and liver function, and blood lipids.

These findings are important, but they should be interpreted carefully. They describe population-level patterns rather than a reliable timetable for an individual woman. They do not establish that every woman will experience these changes or that every abnormal laboratory result is caused by menopause.

Why Does Early Awareness Matter?

Recognising the menopause transition can help women and their doctors plan appropriate care before symptoms become disruptive.

Depending on age, symptoms and medical history, a healthcare professional may recommend:

• Reviewing menstrual changes and discussing symptoms.

• Assessing bone health and osteoporosis risk when appropriate.

• Monitoring blood pressure, cholesterol and other cardiovascular risk factors.

• Evaluating persistent fatigue or other symptoms for alternative causes.

• Discussing treatments for troublesome hot flashes, sleep problems or other menopause-related symptoms.

Routine hormone testing is not necessary for every woman experiencing typical menopause symptoms, particularly over the age of 45. AMH testing is also not a dependable way to predict the exact date of menopause for an individual.

Hormone therapy can be effective for certain menopause symptoms, but it is not suitable for everyone. Decisions should be made with a qualified healthcare professional after considering individual benefits, risks and medical history.

Conclusion

Menopause involves much more than the end of menstrual periods. Hormonal changes can begin years earlier, and the transition may coincide with changes in sleep, temperature regulation, bone health and metabolic markers.

Research involving more than one million women has provided valuable insights into these patterns, helping scientists understand how the menopause transition unfolds across different body systems.

The key takeaway is not that every woman will experience five warning signs 15 years in advance. Rather, women should understand their bodies, avoid dismissing persistent symptoms and seek medical advice when changes affect their health or quality of life. Early awareness and appropriate preventive care can make the transition easier to manage.