Period & Health

Written by: Katrine Svensmark

The Intersection of Science and Women's Hormonal Cycles - A Comprehensive Analysis of Female Sex Hormones, Ovaries, and Hormone Production

The menstrual cycle is a complex and fascinating process that has puzzled scientists and women for centuries. This article aims to comprehensively explore menstruation, delving deep into the science behind women’s hormonal cycles and the intricate interplay between their sex hormones, ovaries, and hormone production. By examining this topic from a scientific perspective, we can gain a better understanding of the menstrual cycle. Furthermore, we will discuss the latest innovations in women’s health technology, such as Gals Bio’s Tulipon, which is designed to screen women’s wellness and health based on biomarkers found in menstrual blood.

Hormonal Regulation of Reproduction: The Hypothalamus-Pituitary-Ovary Axis

The female hormones are regulated through the hypothalamus-pituitary-ovary axis. This system involves the hypothalamic gonadotropin-releasing hormone (GnRH), the pituitary hormones follicle-stimulating hormone (FSH) and luteinizing hormone (LH), and the steroid hormones estrogen and progesterone, which are produced in the ovaries. GnRH is responsible for the production of the pituitary hormones, where FSH primarily controls the formation of estrogen, but LH also plays a role. The woman’s eggs are packed into a small unit called a follicle in the ovaries.

The Intricate Interplay of Hormones in the Ovaries During a Menstrual Cycle

During the menstrual cycle, the ovaries go through two phases. The follicular phase and the luteal phase.

The follicular phase:

is the first half of the menstrual cycle. It starts on the 1st day of menstruation and lasts until ovulation, which is approximately 14 days. In this phase, a follicle matures an egg and produces estrogen. Before ovulation, the follicle bursts, and the mature egg is released.

The luteal phase:

The cells from the empty follicle live on the corpus luteum, and the luteal phase now begins. The corpus luteum functions as an endocrine gland in that the theca and granulosa cells produce progesterone in large quantities and estrogen to a lesser extent. The two hormones now again keep the FSH and LH levels down through negative feedback. After about 11 days, the corpus luteum begins to lose its function, whereby progesterone, and estrogen levels fall and menstruation begins.

Understanding the Three Phases of the Endometrium and Uterus During a Menstrual Cycle

The endometrium changes throughout the menstrual cycle, which is divided into three phases.

Phase 1: The period begins due to the falling levels of progesterone and estrogen, which prevent the maintenance of the mucous membrane. The membrane is loosened at the basement and excreted through bleeding.

Phase 2: The growth phase is characterized by the rising levels of estrogen, which stimulate the new thin lining to grow thicker.

Phase 3: The secretory phase coincides with the luteal phase of the ovaries. The mucosa cells develop into secretory cells, controlled by the rising level of progesterone, which prepares the mucosa to receive a fertilized egg.

Hormonal Regulation of the Menstrual Cycle: The Role of GnRH, FSH, LH, Estrogen, Progesterone, and Inhibin B

A woman produces the hypothalamic hormone GnRH, the pituitary hormones FSH and LH, and the steroid hormones estrogen and progesterone, which are produced in the ovaries.

Schematic sketch of the female hormonal cycle
Schematic sketch of the female hormonal cycle

Schematic sketch of the female hormonal cycle

The egg is surrounded by a unit called a follicle, consisting of theca cells and granulosa cells. Together, they convert cholesterol into estrogen. LH controls the process by stimulating theca cells to convert cholesterol into progesterone and then androstenedione. Granulosa cells convert androstenedione into estrogen. FSH controls the activity of aromatase, the enzyme responsible for converting androstenedione to estrogen. Granulosa cells depend on theca cells for androstenedione production. Estrogen is released into the blood and follicles.

After ovulation, both theca and granulosa cells in the ovaries change their hormone synthesis. More enzymes involved in progesterone production are formed, while the enzymes involved in estrogen production decrease. The structure of the follicle also changes, allowing granulosa cells to absorb cholesterol from the blood and produce progesterone. In addition, inhibin B, a peptide hormone, is formed in the ovaries and negatively affects the production of FSH by the pituitary gland.

Understanding Positive and Negative Feedback in Biological Systems

Positive feedback is when changes in a system lead to further and increased changes – e.g. when a child is breastfed by its mother, the fact that the child is breastfeeding sends signals for the mother to produce more milk.

Negative feedback is not circular like positive feedback is, but are processes that are initiated to compensate for changes in a system.

Negative feedback is happening, for example, in homeostasis – where the internal environment is kept constant. An example could be body temperature. Here, the body tries to keep the body temperature at around 37 degrees. If external factors affect the body temperature, such as hot weather, it will set some processes in motion that cause the body temperature to drop (e.g. you start to sweat, where the sweat then evaporates and lowers the temperature).

Monitoring women’s health through “Mother Nature’s Monthly Gift”

Gals Bio is working towards the goal of improving women’s health and wellness by providing innovative products that can monitor and analyze the hormonal cycle through menstruation. Studies have shown that menstrual fluids can indicate biomarkers for disorder and;

“In 2012, Siegel D, et al. defined the proteomics of menstrual blood and discovered that several biomarkers for a wide range of disorders were present in menstrual fluid. These disorders include endometriosis, breast, cervical, ovarian, and endometrial cancer.” (Naseri, Lerma, Blumenthal; 2019)

That’s why Tulipon, Gals Bio’s latest product, aims to potentially screen women’s wellness and health in the future, using biomarkers found in menstrual blood. By analyzing these biomarkers, Tulipon has the potential to provide valuable insights into a woman’s hormonal cycle, which could help women understand their bodies and potentially improve their overall health and wellness.

Empowering Women Through Understanding: The Importance of Menstrual Cycle Education

In conclusion, the menstrual cycle is a complex and multifaceted process that is critical to women’s health and reproductive systems. By exploring the science behind menstruation and women’s hormonal cycles, we can gain a deeper appreciation for the intricate interplay between the female sex hormones, ovaries, and hormone production. Gals Bio’s newest product, Tulipon, is designed to help women better understand their bodies and take control of their health and well-being. By collecting vaginal effluents and screening women’s wellness and health based on biomarkers found in menstrual blood, Tulipon has the potential to provide valuable insights into a woman’s hormonal cycle. As we continue to unravel the mysteries of menstruation, innovative products like Tulipon give us hope for a brighter future for women’s health and reproductive rights.


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  9. Sara Naseri, Klaira Lerma, and Paul D. Blumenthal. (2019, November 20) Comparative Assessment of Serum versus Menstrual Blood for Diagnostic Purposes: A Pilot Study.

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