The menstrual cycle is an intricate dance of hormones orchestrated with exquisite precision. At the forefront of this hormonal ballet stands estrogen, a versatile and enigmatic hormone with a significant role in the female reproductive system. 

For today’s article, we consulted with women health professionals from Uptown Pharmacy to guide you through the captivating behavior of estrogen throughout the menstrual cycle. We’ll unravel its multiple roles, fluctuations, and how it influences the ever-changing landscape of a woman’s body.

Estrogen: the main hormone of the menstrual cycle

Estrogen, a collective term for the hormones estradiol, estrone, and estriol, is a hormone present in both the male and female sexual reproductive systems. This hormone is primarily produced by the ovaries, with smaller amounts emerging from the adrenal glands and fat cells. Estrogen primarily contributes to reproductive and breast health. When it comes to the menstrual cycle, its behavior is anything but static, evolving throughout the cycle in response to a complex interplay of signals and feedback mechanisms. 

The menstrual cycle itself

The menstrual cycle unfolds in four distinct phases:

  • Menstruation
  • Follicular phase
  • Ovulation
  • Luteal phase 

Estrogen’s performance is particularly striking in the follicular and luteal phases, each with unique fluctuations and processes.

Follicular phase

The cycle begins with menstruation, marked by a decrease in estrogen levels. As the menstrual bleeding subsides, the follicular phase commences. During this phase, estrogen’s behavior is characterized by a gradual increase, orchestrated to stimulate the growth and development of ovarian follicles. These follicles house immature eggs, and under estrogen’s guidance, they mature, setting the stage for the cycle’s next act.

Estrogen’s dynamic behavior is not limited to follicular growth. It also plays a role in the thickening of the uterine lining (endometrium) in preparation for a potential pregnancy. 


Ovulation is the process in the menstrual cycle when the egg is released from the ovary, which is the most fertile moment when it comes to the possibility of getting pregnant. Estrogen’s role in ovulation is pivotal and fascinating. Estrogen’s crescendo initiates the menstrual cycle’s show-stopping event. As estrogen levels peak, they signal the release of luteinizing hormone (LH) from the pituitary gland. LH surge activates the release of a mature egg from one of the ovarian follicles, marking the zenith of fertility during the cycle.

Luteal Phase

After ovulation, the luteal phase begins, marked by the continued presence of estrogen and another hormone, progesterone. Together, those hormones prepare the uterine lining for a potential pregnancy. Estrogen maintains the endometrial thickness and blood supply, ensuring the uterine environment is hospitable for implantation.

When pregnancy doesn’t take place, estrogen and progesterone levels eventually decrease, leading to the shedding of the uterine lining and the onset of menstruation, thus completing one cycle and setting the stage for the next.

Factors affecting estrogen levels during the menstrual cycle

Estrogen levels are influenced by a variety of factors, both internal and external, which collectively shape the way this hormone behaves.

  • Age: Estrogen levels change over a woman’s lifespan. They are generally low before puberty, peak during the reproductive years, and decline during perimenopause and menopause.
  • Ovarian function: As mentioned, the ovaries are the main source of estrogen production. Any condition that affects ovarian function, such as polycystic ovary syndrome (PCOS) or premature ovarian insufficiency, can alter estrogen levels.
  • Weight: Adipose tissue can produce small amounts of estrogen. Consequently, women with higher body fat percentages may have slightly higher estrogen levels. Conversely, low body fat, as seen in athletes or individuals with eating disorders, can lead to lower estrogen levels.
  • Medications: Certain medications, like hormonal contraceptives or hormone replacement therapy, can affect estrogen levels. 
  • Stress: Chronic stress can disrupt hormone balance, affecting the menstrual cycle and potentially leading to changes in estrogen levels.

Estrogen role beyond the menstrual cycle

Estrogen’s influence extends beyond the menstrual cycle. It is responsible for developing secondary sexual characteristics and plays a significant role in maintaining bone density and cardiovascular health. Estrogen also affects mood and cognitive function, underscoring its broad impact on a woman’s overall well-being.

Final thoughts 

Estrogen behavior throughout the menstrual cycle is a testament to the remarkable complexity and precision of the female reproductive system. Its role in promoting follicular development, making ovulation possible, and preparing the uterine environment for potential pregnancy is the truest magnificence. Understanding the dynamic behavior of estrogen is essential not only for reproductive health but also for appreciating its multifaceted impact on a woman’s physical and emotional well-being.