Menopause and Perimenopause

Sex hormones & fertility in the different phases of a woman’s life

From puberty onwards, in each cycle, which usually lasts 25 to 35 days, one or more fertilizable egg cells mature in the ovaries in so-called follicles. The largest follicle bursts around the middle of the cycle (aka ovulation) and the egg is flushed into the fallopian tube and moved towards the uterus. At the same time, the lining of the uterus prepares for the implantation of a fertilized egg. If the egg does not nest or dies, the lining of the uterus is shed and menstrual bleeding occurs. A new cycle begins.

Two of the most important female sex hormones are estrogens and progesterone, which are produced mainly in the ovaries and in small quantities also in the adrenal cortex and in the fatty and other tissues. In addition, male hormones, the androgens, are also produced in the ovaries and adrenal cortex from puberty onwards. The most important of these is testosterone. The process of estrogen and progesterone production and the maturation of the eggs in the ovaries are stimulated by superordinate hormone control centres, the hypothalamus and the pituitary gland. This takes place via the so-called gonadotropins: your Luteinizing Hormone and Follicle-Stimulating Hormone

Women have a fixed and therefore finite number of follicles in their ovaries though. During sexual maturity, the ovules in the ovaries are almost completely used up. If a girl has up to 400,000 developable eggs in her ovaries at birth, this supply is used up by the time she enters menopause. And as fewer and fewer follicles mature in the ovaries or their responsiveness diminishes, the hormonal control cycle is altered. As a result, ovulation and the corpus luteum phase are increasingly absent. The production and release of Progesterone (or corpus luteum hormone) in the second half of the cycle ebbs away until finally Estrogen production in the ovaries also comes to a standstill. Estrogens are still produced to a small extent in the adrenal cortex and fatty tissue. Towards the end of postmenopause, about 15 years after its onset, the production of gonadotropins in the pituitary gland also decreases.

What exactly is Perimenopause?

As the name already suggests, Perimenopause is not the same as menopause. Perimenopause happens around the time a woman passes from childbearing age to menopause. Menopause occurs when a woman has not had a period for more than a year. You could therefore define Perimenopause as the transition into menopause. In Western countries, the average at menopause is 51, although this timing can be influenced by your lifestyle, ethnicity, genes and environment.

Perimenopause and estrogen dominance

Menopause is usually announced by cycle disorders such as a shortening of the cycle or irregular bleeding intervals. In women in this phase of life, ovulations become increasingly irregular and there are cycles with and without ovulation. The latter increase with increasing proximity to menopause. The length of the cycle and the duration of bleeding also fluctuate frequently. While in early perimenopause the cycles differ by up to seven days from the cycle lengths before, phases of ≥ 60 days of no menstruation are typical of late perimenopause.

During the fertile years, the monthly maturing follicles, stimulated by the control hormones of the pituitary gland Luteinizing Hormone LH and Follicle-Stimulating Hormone FSH, produce the hormone estrogen. In the first half of the cycle the Estrogen level rises, while after ovulation, in the second half of the cycle, the production of Progesterone in the ovaries increases (aka corpus luteum or luteal phase).

Perimenopause is characterized by a decrease in ovarian function (ovarian function). As soon as the tiring ovaries react less to the control hormones, there is an increased release of your Follicle-Stimulating Hormone (FSH). This again strongly stimulates follicle maturation and thus estrogen production during these cycles. This results in higher estrogen levels from the 3rd week of the cycle in particular. Progesterone levels on the other hand, rise only slightly in this phase of the cycle, so that there is a simultaneous Progesterone deficiency. This relative excess of estrogen is also known as estrogen dominance, to express that in this situation estrogen plays a predominant role in the body because the regulating progesterone is only present in a smaller proportion.

As a result of estrogen dominance, many women report experiencing a strong feeling of tightness in the breasts in the second half of the cycle and increased menstrual bleeding, possibly accompanied by lower abdominal pain and pre-bleeding. A drop in estrogen levels within a few days from very high to very low can also cause hot flashes in women before the cycle starts again.

An average hormone cycle during the fertile years

Estrogen deficiency in menopause

Gradually the number of stimulable follicles still available in the ovaries decreases and at some point this tissue is used up. The ovaries, which have steadily reduced their activity, eventually stop producing female hormones altogether. Cycle and menstruation stop. Symptoms of Estrogen deficiency can occur. If menstruation stops for weeks or months, this does not necessarily mean that the ovaries stop working. Only when there has been no menstrual bleeding for a year can it be assumed that menopause has been reached.

As long as the ovaries are still functioning, a possibly strongly fluctuating ovarian activity can be accompanied by changing estrogen deficiency symptoms which can range from mood swings to painful sex due to a lack of vaginal lubrication and mental health problems such as depression.

What factors are there that can influence the timing of menopause?

Menopause begins when the supply of egg cells that Mother Nature has given us in the ovary runs out. This egg cell stock is created during pregnancy, i.e. already in the female embryo or fetus. In other words, this supply also depends on the influences to which your own mother was exposed during pregnancy: did she receive harmful medication? Was she exposed to radiation? Was she malnourished? Did she smoke? All these things are usually difficult to find out in retrospect but have an influence on your supply of egg cells.

The time of menopause is shifted forwards or backwards by accelerated or delayed egg cell death. It has been clearly proven that smoking (presumably due to a reduced oxygen supply to the ovary) is associated with a statistically significant earlier menopause. Patients who have undergone surgery in the uterus or ovaries or fallopian tubes also enter the menopause somewhat earlier on average. This is very obvious for women who have had an entire ovary removed. However, women who have had their uterus removed or who have had a sterilisation (i.e. still have both ovaries) can also be expected to reach menopause a little earlier on average. This is probably also a consequence of reduced blood flow to the ovaries as a result of vascular blockages caused by surgery. However, none of the factors mentioned will bring forward the onset of the menopause by more than 1 to 2 years.

On the other hand, aggressive chemotherapy or radiation in the lower abdomen can cause irreversible damage to the ovaries. This affects all women of fertile age equally. The more aggressive the chemotherapy and the older the patient is during treatment, the higher the risk of lasting damage to the ovaries with the consequence of a complete loss of ovarian function. Other causes of early menopause are much rarer, including autoimmune diseases, viral infections (e.g. mumps), metabolic diseases and genetic disorders (e.g. Turner syndrome).

Apparently another factor also influences when women enter the menopause: An active sex life is associated with a rather late onset of the menopause, according to a statistical study. It is possible that this tendency reflects the fact that the female body is oriented towards the probability of conception, researchers say.

As much as we want to deny it: At some point, menopause definitely comes - there is no natural behavioural intervention that can prevent the end of female fertility. Nevertheless, the results of the mentioned study might be a first indication that the timing of the menopause is, to a certain extent, linked to the probability of becoming pregnant.

Other sources:

Hoyt, Lindsay Till, and April M Falconi. “Puberty and perimenopause: reproductive transitions and their implications for women's health.” Social science & medicine (1982) vol. 132 (2015)