Understanding Your Hormones

From Module 2 of Navigate Menopause

Lesson: Your Lifelong Hormonal Journey: The Beginning with Dr. Carla DiGirolamo

Your hormonal journey starts in puberty, which in females generally begins between the ages of 8 and 13, though it can vary widely. It begins with the release of hormones from the hypothalamus, pituitary gland, and ovaries, which trigger a series of physical and physiological changes.

There are many changes that occur during puberty. You develop breasts, your hips widen, you have an increase in body fat, and of course, you get your period. Menstruation typically begins with irregular periods, which become more regular over time. 

Along with these obvious physical changes, girls may also experience emotional and psychological changes during puberty. Hormonal fluctuations can contribute to mood swings and changes in body image and self-esteem. (Sound familiar? When you sit and think about it, it’s crazy that all of this is so natural and expected at puberty, but decades down the road when we hit puberty in reverse during the menopause transition, we get crickets…)

The menstrual cycle generally falls into a fairly rhythmic, predictable pattern during a woman’s premenopausal years. The two main ovarian hormones that drive what we experience are estrogen and progesterone. But there are other players involved as well, including gonadotropin-releasing hormone (GnRH), follicle-stimulating hormone (FSH), and luteinizing hormone (LH).

The Phases of the Menstrual Cycle

Follicular Phase:

• The menstrual cycle begins with the follicular phase, which starts on the first day of your period. The hypothalamus in the brain releases gonadotropin-releasing hormone (GnRH), stimulating the pituitary gland to release follicle-stimulating hormone (FSH).
• FSH prompts several ovarian follicles to develop. These follicles contain immature eggs.
• As the follicles grow, they produce estrogen, primarily estradiol, which thickens the uterine lining (endometrium) in preparation for potential implantation.

Ovulation:

• The rising estrogen levels trigger a surge in luteinizing hormone (LH) from the pituitary gland, which leads to the release of a mature egg from the dominant follicle, aka ovulation.
• Ovulation typically occurs around the middle of the menstrual cycle, approximately 14 days before the next menstrual period.
 

Luteal Phase:

• After ovulation, the ruptured follicle transforms into the corpus luteum, a temporary endocrine structure in the ovary.
• The corpus luteum secretes progesterone, along with small amounts of estrogen.
• Progesterone prepares the uterus for potential implantation by thickening the endometrium further and promoting the secretion of nutrients.
• If fertilization occurs, the trophoblastic cells that ultimately become the placenta produce human chorionic gonadotropin to let the body know there’s a fetus and we need progesterone to maintain the pregnancy. 
• If fertilization and implantation do not occur, the corpus luteum degenerates, progesterone and estrogen levels drop, and the menstrual phase begins again.

This whole process is orchestrated by your hormones, which are messengers sending signals to receptors on tissues. They receive those messages, and act accordingly. The chart below shows the process starting with when the brain says it’s time to make an egg!

As the chart below shows, this all happens in a rhythmic, predictable hormonal pattern for our premenopausal lives (realizing that we aren’t machines and our cycles can vary from time to time and are influenced by various factors such as stress, hormonal imbalances, medical conditions, and of course pregnancy, which we’ll discuss in Module 4 in hormone therapies).  

When our ovaries start shutting down production, the hormonal conversation becomes chaotic and unpredictable, which is the hallmark of what we know as perimenopause.

This increasingly chaotic hormonal conversation of perimenopause and the following “flatline” in the conversation post menopause don’t just impact our menstrual cycle, which they most certainly do, but also can have a profound impact on other systems in our body, which we’ll cover in more detail in the following section.