While the experience of pain is multi-factorial, recent studies have suggested that the pain experience may be due to the expression of sex hormone receptors in the fascial tissues.
I had a total hysterectomy in my late 40’s. I had a huge ovarian cyst which had become so large it was beginning to affect my internal organs and my daily function.
When I first heard Dr Carla Stecco present this research at the MyoPain conference in India in 2017, it really piqued my interest. I had experienced more pain than usual since my hysterectomy 1 year previously. To think that hormones could contribute to pain is not an entirely new field of research. However, to have some supportive evidence that hormones may play a role in myofascial pain syndromes could enhance the way that we treat our clients.
Pregnancy, for many women, reduces their everyday daily pain experience while for others, back pain is prevalent. Many women experience an increase in pain levels during menopause, and some women experience more sporting injuries during certain phases of their menstrual cycle.
‘It is known, in fact, that estrogen and relaxin play a key role in extracellular matrix remodeling by inhibiting fibrosis and inflammatory activities, both important factors affecting fascial stiffness and sensitization of fascial nociceptors.’
“If the connective tissue is altered, the behavior of the fascia and underlying muscle becomes compromised, being source of myofascial disorders in many cases.”
How do hormones affect the fascia?
The fascia is comprised of 2 main types of collagen, collagen I and collagen III. Type I collagen is the most abundant collagen in the body found in tendons, skin, artery walls, cornea, the endomysium surrounding muscle fibres, fibrocartilage, and the organic part of bones and teeth. It is also found in scar tissue. Type III collagen is found in artery walls, skin, intestines and the uterus. It is also found in granulation tissue, the immature tissue that helps heal a wound.
Collagen I provides the fascial tissue with strength and resistance of tensile stressors. In contrast, collagen III provides a degree of elasticity. The extracellular matrix (ECM) comprising the collagen fibres along with proteoglycans, glycosaminoglycans, elastin, fibronectin creates a dynamic tissue environment. It supports, protects, separates and binds all other body structures. The ECM also plays a contributing role in movement, coordination and function.
The most simple analogy is to view the fibres and the ECM as a casserole dish of meat and vegetable stew in gravy. The meat is the collagen, the vegetables are the other fibres, such as elastin and fibronectin and, the gravy is the gel-like ground substance. The gravy connects all the components together but, at the same time, creates separation.
Collagen is produced by fibroblasts, specialised cells within the fascial tissues. Fibroblasts also produce glycosaminoglycans and proteoglycans for the ECM. You may know the ECM as the ‘ground substance’. Fibroblasts have receptors on their cell surface, allowing them to respond to their environment. Some receptors respond to hormone levels such as oestrogen and relaxin. Cell receptor signalling causes a cell to function in a particular way. Hormone levels within the fascial tissue will cause fibroblasts to produce more or less collagen, glycosaminoglycans and proteoglycans.
Fede et al., (2016) and (2019) conducted in vitro (tissue specimens in a lab) research. They discovered that sex hormone levels did affect the composition of fascial tissues.
They found that when sex hormone levels were decreased, collagen type I levels increased. Since collagen type I is involved in tissue stiffness, this research suggests that when women experience a decrease in sex hormones during menopause, the fascia becomes denser.
When fascia is dense, it compresses nerves, specifically nociceptors. Nociceptors respond to tissue damage and, when compressed, send action potentials via the dorsal horn to the brain that is recognised as pain.
Conversely, their research also concluded that when sex hormone levels increased, the fascial tissues became more lax and elastic due. This was due to the resultant increased production of collagen type III and less collagen type I.
This also corresponds with previous research where female athletes and sportspersons experienced more injury during their menstrual cycle when sex hormone levels were higher.
Back pain during pregnancy is common. The thoracolumbar fascia is responsible for load transfer between the legs, pelvis, sacrum, lumbar and thorax. It assists in the generation of movement and ‘force closure’ of the pelvic bones and sacrum. Levels of sex hormones can increase during pregnancy resulting in more collagen type III and less collagen type I. This suggests that when tissue tension is decreased, the is load is also reduced from the sensitised nociceptors. This could be a reason why pregnant women experience less general pain.
However, as the thoracolumbar fascia requires strength to support movement, an increase in sex hormone may result in an increase of collagen type III and a decrease of collagen type I. This could alter the ability of the thoracolumbar fascia to control and stabilise movement, resulting in back pain.
Fede et al., (2016) and (2019) concludes that the administration of oestrogen (HRT) in postmenopausal women could decrease pain experience. However, they also recognise that their research is preliminary, and further in-vivo trials would need to be considered.
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Fede, C., Albertin, G., Petrelli, L., Sfriso, M., Biz, C., De Caro, R., Stecco, C. (2016) ‘Hormone Receptor Expression in Human Fascial Tissue’, European Journal of Histochemistry , vol. 60, nbr, 4, p. 2710. Available at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5134680/ (Accessed 18 November 2020).
Fede, C., Pirri, C., Fan, C., Albertin, G., Porzionato, A., Macchi, V., De Caro, R., Stecco, C. (2019) ‘Sensitivity of the fasciae to sex hormone levels: Modulation of collagen-I, collagen-III and fibrillin production’, PLOS ONE,vol, 14, nbr. 9. Available at https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0223195(Accessed 18 November 2020).