Is fascia affected by sex hormones?

Groundbreaking new research shows how collagen production throughout the body is affected by sex hormones, such as estrogen. Simply explained, the hormones “tell” the fibroblasts to reduce the production of collagen type I and increase the production of collagen type III during both ovulation and pregnancy. This can result in pain and other problems, partly because the “remodeling” itself can be painful, but it gets worse if you are exposed to heavy load, when you have a deficit in collagen type I.


Fascia guide’s Camilla Ranje Nordin has taken a deep dive into the latest research on fascia and hormonal influence and explains the different course of events in the article below.

Fascia is the elastic, continuous network in the body, which extends from the surface of the skin, down to the membrane of every cell – and is also in contact with the cell nucleus through the cytoskeleton. Fascia is the structure outside the cells, the extracellular matrix, which mainly includes fiber proteins, such as collagen and elastin, as well as the liquid ground substance, consisting mainly of hyaluronic acid and other glycosaminoglycans and a lot of water.


A commonly occurring cell type, which is central to the construction of this structure, of the entire structure of the body, are fibroblasts. Among other things, they produce the protein collagen. Collagen contributes to structure and strength and controls the mechanical properties of the fascia on a macro level.


It is the collagen, which is needed for strength, that varies in strength during different stages of the menstrual cycle. But what is really going on?


First of all … what you need to know about collagen

Collagen is the body’s most abundant protein and collagen comes in several different varieties, for example type I, which is our most common collagen, or type III which is a softer collagen, common in loose, areolar fascia.


Type I collagen is a strong, stable collagen that forms strong fibers, actually stronger than steel. That type is abundant in deeper, dense and strong fascia, e.g. tendons, ligaments, myofascia and the strong aponeurosis fasciae over e.g. abdomen and back, the rectus fascia and the thoracolumbar fascia. They should help to strengthen and stabilize our posture.

In looser fascia, e.g. under the skin and between sliding layers of dense fascia, there is instead more collagen type III, together with more fluid ground substance.


For the collagen fibers to become strong, so-called cross-links are needed between the collagen molecules to hold together and stabilize the fibers. As with most things when the body needs to synthesize something, enzymes are needed to drive the synthesis. An enzyme that helps create cross-links in collagen I is called lysyl oxidase, and it is needed to create a stable and strong collagen structure.


A lot of crosslinks give a more stable, but also stiffer, collagen and fewer crosslinks give a softer, less stable collagen.

How is Fascia affected by sex hormones?

The fibroblasts respond to estrogen

Fede et al, have shown that the fibroblasts have special receptors that react to the hormone estrogen. When the hormone attaches to the cell receptor, the cell receives a signal what to be produced and how it should look like. Estrogen has a major impact on how the cell’s collagen production should proceed.

The hormone estrogen thus affects the connective tissues composition of collagen, which of course affects all fascia, tendons, ligaments and more. It has been investigated how the fascia is affected by the hormones estrogen and relaxin, in amounts corresponding to different stages of the menstrual cycle, as well as after menopause.


Variations during the menstrual cycle

The collagen composition thus varies during the menstrual cycle. For the first two weeks of the cycle, estrogen production is lower to increase and peak around ovulation and then decrease again during the corpus luteum phase and then start again at lower levels until the next follicular phase.

If it then continues with a pregnancy, the estrogen level gradually increases again to very high levels.

The hormone relaxin is at a fairly low level until after ovulation and the corpus luteum phase when it increases, so that in the event of pregnancy it increases by 200 times, compared to before ovulation. After menopause, relaxin production ceases, and estrogen production also decreases and continues to be very low.

An increase in estrogen levels also decreases the production of collagen I and instead increases the formation of collagen III and fibrillin (another protein in fascia, precursor to elastin). This would contribute to a softer and less stable fascia.


Hormones interact and influence each other


Now it is not quite that simple as it is not only estrogen that affects collagen formation, but many hormones interact and affect each other.

This variation of collagen type due to estrogen is evened out by the hormone relaxin, which was also investigated by Fede et al. Relaxin is a hormone that participates in the breakdown and rebuilding of the extracellular matrix, among other things it reduces collagen production and counteracts fibrosis and inflammation. This applies to many organs in the body such as the heart, lungs, liver etc.

The variation of collagen and fibrillin during the menstrual cycle is therefore not as marked, with the influence of relaxin, but is a little more stable with a small excess of collagen I compared to collagen III throughout the cycle. Right up until pregnancy when collagen I decreases and collagen III increases. Now it is needed a soft and malleable fascia that can yield without being damaged.


More estrogen = fewer crosslinks


Research has also shown that the enzyme lysyl oxidase is inhibited by estrogen. As I wrote above, lysyl oxidase should help create cross-links in the collagen. Thus, not as many cross-links are formed when there is a lot of estrogen. This means that a weaker, less stable collagen is formed, especially around ovulation and during pregnancy, when estrogen levels are high.

The structural remodeling of collagen proceeds very quickly and a reduction of the enzymes effect by 77% within 48 hours has been found. At the same time, no change has been found in the amount of collagen.

An explanation for increased back pain during pregnancy

This can result in an increased tendency to back pain, sprains, or cruciate ligament injuries, but instead gives the advantage of fewer muscle tears as the collagen of the tendons and muscle fascia is more elastic. Especially during pregnancy, it is common to have back pain, when the tissue is weakened and the muscles and fascia are also easily overstrained, because the center of gravity changes and the body ends up out of balance.

An overstretched fascia creates small micro-damages, which initiates a healing process, an inflammation, in which hyaluronic acid is highly involved (see article on hyaluronic acid and densification). This inflammation and densification of the fascia also creates pressure on nerve receptors and can then signal pain.

More estrogen & contraceptive pills = worse effect of training

Production and breakdown of collagen, formation of new tissue, is stimulated by stress, so more collagen is formed when you exercise. The body adapts to what is required. Here too, there is an influence of estrogen. Hansen et al. have found that collagen synthesis after a training session is inhibited by high estrogen levels, which means that during periods of high estrogen levels, the body does not respond as effectively to training.

High estrogen levels can also occur in women taking contraceptive pills with estrogen. It can then impair the effect of training and the stability and strength of all types of fascia, tendons and ligaments. Something to keep in mind for female athletes taking that type of pills.

What happens after menopause?

After menopause, when estrogen levels drop, the production of collagen I increases in relation to collagen III which decreases, and also fibrillin decreases. Then the fascia instead becomes stiffer, albeit firmer, which can also create back pain and other myofascial pain due to too tight a suit that presses on pain receptors in the fascia.

Fascia treatment to keep the fluid flow in the liquid part of the fascia, can reduce stiffness caused by densification of the hyaluronic acid. This will increase the gliding and lubricating function, to bring the body into balance, and can reduce problems!

  • Fede et al, 2016. Hormone receptor expression in human fascial tissue.
  • Fede et al, 2019. Sensitivity of the fasciae to sex hormone levels: Modulation of collagen-I, collagen-III and fibrillin production.
  • Hansen et al, 2008. Ethinyl oestradiol administration in women suppresses synthesis of collagen in tendon in response to exercise
  • Kjær et al, 2009. Mechanical loading, tendon, collagen synthesis, tissue adaptation, fibroblast, growth factors, exercise, physical training
  • Lee et al, 2015. Estrogen Inhibits Lysyl Oxidase and Decreases Mechanical Function in Engineered Ligaments.
  • Lodish et al, 2000. Molecular Cell Biology, 4th edn.