Hormone changes during the menopause journey

Symptoms you may experience during your menopause journey are largely the result of changes in some of your key hormone levels, most notably estrogen. However, a range of interacting hormones are involved in the female reproductive cycle and their levels start to change as menopause approaches.

Throughout much of your reproductive years it is likely that your hormones follow a cyclic pattern of rise and fall on a roughly monthly basis, which helps to regulate the menstrual cycle and preparing your body for possible pregnancy.¹ As you approach menopause, this cyclic pattern starts to become more erratic, which can lead to irregular periods, as well as different symptoms ranging from hot flashes, to difficulty sleeping.

There are a number of hormones whose levels are often of interest to healthcare professionals during the menopause journey and they may wish to check your levels of some to help them understand where you are.

Follicle Stimulating Hormone (FSH)

FSH is made in the brain by the pituitary gland and is one of the main hormones that healthcare professionals may look at in relation to menopause. It supports estrogen production and other reproductive processes. Follicle stimulating hormone, as its name implies, stimulates follicles (immature eggs which sit in a small fluid-filled sac in the ovary) to mature such that one will eventually be released, in a process called ovulation, and is available to be fertilized by a sperm if one happens to be passing.

Women are born with their full supply of follicles (around 2 million) and as they age, their number of follicles decreases. FSH production increases in response to the declining number of follicles to try and encourage more follicles to mature and induce ovulation.^2,3 This is why increased levels of FSH are often used as an indicator of approaching menopause.

Estrogen

Estrogen is a very important female sex hormone as it promotes the growth and health of reproductive organs.⁴ Its role includes:

• encouraging lubrication and maintaining blood flow to the vagina
• changes cervical mucus to make it more sperm friendly
• stimulating the uterus lining to thicken
• keeping the vaginal lining elastic
• triggering the luteinizing hormone surge
• stimulating breast tissue growth
• and other functions including preserving bone density

High levels of estrogen can lead to bloating and breast tenderness whereas low levels can result in hot flashes, vaginal dryness and many of the other symptoms associated with the menopause journey.⁴

Estrogen is produced by the follicles in the ovaries with levels rising and falling in a cyclical pattern throughout the menstrual cycle. When your estrogen level rises, it triggers FSH production to stop and causes a sudden rise in LH (called the LH surge), which in turn triggers ovulation to occur within the next 24 – 36 hours.^5,6 However, estrogen levels decline along with the quantity of follicles as you approach menopause. This results in estrogen levels fluctuating unpredictably as you approach menopause and FSH levels to elevate.

Luteinizing Hormone (LH)

LH, like FSH, is produced in the pituitary gland in the brain. The surge in LH that happens in response to rising estrogen levels triggers ovulation to occur within the following 24-36 hours and thereafter LH causes the corpus luteum, (a temporary hormone-secreting gland that forms from a ruptured follicle that has released an egg), to release progesterone, another key sex hormone, important in maintaining the womb lining in case of pregnancy.^6,7

As you approach menopause, LH becomes significantly elevated 3 to 4 years before menopause.⁸ LH will continue to rise in postmenopause as the ovaries are no longer responsive to the hormone.⁹

Progesterone

In common with other sex hormones, progesterone levels change throughout the menstrual cycle and its highest concentration is during the second half of the menstrual cycle (after ovulation). It’s produced by the corpus luteum, preparing your womb (uterus) for the possible implantation of a fertilized egg. If this does not happen, the corpus luteum breaks down and progesterone levels fall. This in turn causes the lining of the womb to break down and triggers your period.¹⁰ As menopause approaches, progesterone production reduces which can lead to the uterine lining becoming thicker before its shed, resulting in heavy periods for some women.⁵

Inhibin B

Inhibin B is another hormone whose levels fall as menopause approaches. Inhibin B is also produced by follicles in the ovaries and its role involves communicating to the pituitary gland to produce less FSH. Therefore, as follicle numbers decline and inhibin B levels fall, FSH production is no longer suppressed and so continues to rise.³

Anti-Müllerian Hormone (AMH)

AMH is another hormone produced by small developing follicles in the ovaries. It gradually declines over time as the number of follicles decrease with age. AMH levels can be used to check for premature menopause (before age 40) and early menopause (before age 45). Low AMH in your blood may be helpful to determine if you are approaching menopause but can’t predict when it will actually happen. If you are under 40 with symptoms of perimenopause, low blood AMH levels may indicate primary ovarian insufficiency.¹¹

Testosterone

Testosterone is commonly thought as a male hormone, however, it plays an important role for women too. Most testosterone is produced by your ovaries, but as you approach menopause, they produce less and less of it. Testosterone is the main hormone which fuels your sex drive¹² however it also affects your mood, muscles, bones¹³ and sleep patterns.¹⁴ Therefore, as it decreases you may experience decreased sexual desire, irritability, anger, stress, fatigue, joint pain, weakness due to decreasing muscle strength¹⁵ and changes in your sleep duration and quality¹⁶, meaning you could find yourself sleeping for fewer hours at night or you could wake up in the morning still feel tired.

Overall, the changes you experience in your hormone levels throughout your menopause journey may lead to symptoms and make you feel ‘not like yourself’. With a little more information about how the different hormones fit together in the menstrual cycle and how they can change during the menopause journey, it may help you understand more about any tests or treatments your healthcare professional might be considering.