Why Does Perimenopause Happen?
This is the second article in our series demystifying perimenopause. Previously, we explored what perimenopause is and why many women find this transition challenging to understand and discuss. Today, we delve into the underlying causes: Why does perimenopause happen?
The Biology Behind Perimenopause
Perimenopause is a natural stage in a woman’s reproductive life, signalling the approach of menopause when menstrual cycles cease. The root cause of perimenopause is hormonal changes in the body, specifically involving oestrogen and progesterone. As a woman ages, her ovaries gradually decrease their production of these hormones, leading to physical, emotional, and psychological changes.
The Role of Ovarian Aging and Follicle Depletion
Ovarian aging is a key driver of perimenopause. From birth, a woman has a finite number of follicles (small sacs in the ovaries that contain immature eggs). Throughout life, these follicles decrease in number due to regular menstrual cycles and the natural process of follicular atresia (the degeneration of immature follicles).
By the time a woman reaches her mid-to-late 30s, the decline in the number and quality of follicles becomes more pronounced. This decline continues, and by the time perimenopause begins (often around the early-to-mid-40s), the number of follicles is significantly reduced. As a result, the ovaries produce less estrogen, which is one of the main hormones responsible for regulating the menstrual cycle. This decreased production of oestrogen is what triggers the symptoms and irregular cycles typical of perimenopause.
Hormonal Imbalance: Oestrogen and Progesterone
Two hormones play a pivotal role in the reproductive cycle: estrogen and progesterone. During perimenopause, these hormones can fluctuate unpredictably. Oestrogen may rise and fall erratically, and progesterone levels generally decline because fewer ovulations occur. This hormonal imbalance is responsible for many of the symptoms women experience during perimenopause, such as irregular periods, hot flashes, mood swings, and sleep disturbances.
Oestrogen has a significant influence on many systems in the body, including the cardiovascular system, bone density, brain function, and vaginal health. This is why perimenopause can affect multiple aspects of a woman’s health and well-being.
External factors such as stress and lifestyle choices can exacerbate perimenopausal symptoms. Elevated stress levels can impact the hypothalamus-pituitary-ovarian (HPO) axis, which regulates the reproductive hormones. Chronic stress can worsen symptoms like mood changes, hot flashes, and sleep disturbances, making the perimenopausal transition more challenging.
Diet, exercise, and overall health can also play a significant role in symptom severity and hormone regulation. Women with sedentary lifestyles or those who smoke, for example, may experience more intense perimenopausal symptoms.
Genetics and Family History
Genetics play a significant role in determining when a woman may enter perimenopause and how long the transition lasts. Research shows that women are likely to experience perimenopause around the same age as their mother or close female relatives. Additionally, certain genetic variations may predispose women to experience more intense symptoms or an earlier onset of perimenopause.
The variability in timing, duration, and symptoms experienced by women in perimenopause indicates that genetics is a major factor influencing this phase of life.
Environmental and Social Factors
Certain environmental and social factors, such as exposure to toxins, socioeconomic status, and health access, can impact when perimenopause begins and how it progresses. For example, studies have shown that women who have been exposed to chemicals like polychlorinated biphenyls (PCBs) or have had poor nutritional status may experience an earlier onset of perimenopause.
Access to healthcare and support also plays a role in how well women can manage their symptoms and understand the transition. The lack of awareness and education about perimenopause further complicates how women perceive and experience this phase.
The Evolutionary Perspective: Why Does It Happen at All?
An interesting theory in evolutionary biology suggests that menopause and, consequently, perimenopause, have evolved as a life stage for women to invest more energy in caring for their existing offspring and grandchildren, known as the "grandmother hypothesis." This theory posits that perimenopause allows older women to ensure the survival and success of their descendants without the burden of pregnancy and childbearing, particularly in environments where such activities might have become high-risk with age.
Conclusion
Perimenopause is a complex process influenced by a combination of hormonal changes, genetics, lifestyle, and environmental factors. The decline in estrogen and progesterone production due to ovarian aging is the primary biological mechanism, but the experience of perimenopause varies greatly among women due to other influencing factors. Understanding why perimenopause happens is crucial for developing effective management strategies and reducing the stigma and misconceptions surrounding this natural life transition.
In the next article, we will explore how to manage perimenopausal symptoms effectively.
References:
- Richardson, S. J., et al. (1995). "Ovarian follicular depletion during the menopausal transition: Evidence from the Squirrel Monkey." Journal of Clinical Endocrinology & Metabolism, 80(10), 2835-2840. DOI: 10.1210/jc.80.10.2835
- Burger, H. G., Dudley, E. C., Hopper, J. L., et al. (1995). "Prospectively Measured Levels of Serum FSH, Estradiol, and the Proportion of the Cycle Length with Elevated FSH in Menstrual Cycles of Women During the Menopausal Transition." Journal of Clinical Endocrinology & Metabolism, 80(11), 3510-3517. DOI: 10.1210/jc.80.11.3510
- Sowers, M. F., Zheng, H., McConnell, D., et al. (2006). "Follicle Stimulating Hormone and Its Rate of Change in Defining Menopausal Transition Stages." The Journal of Clinical Endocrinology & Metabolism, 91(10), 3958-3964. DOI: 10.1210/jc.2006-1374
- Cramer, D. W., & Xu
