Frozen shoulder and a possible association to thyroid conditions
Your shoulder joint is made up of bones, ligaments and tendons which are wrapped in connective tissue. When the connective tissue thickens, contracts and becomes inflamed it causes pain and increasing stiffness.
Initially your shoulder might be painful but you are still able to move it fairly well. However, the increasingly contracted tissue makes it harder to have any movement and a reduced range of movement causes the tissue to contract – so it is a vicious circle.
As the condition deteriorates the pain mostly decreases but you can hardly move your shoulder. This is commonly called frozen shoulder – a term created in 1934.
Frozen shoulder typically occurs between the ages of 40 and 60 and there is a slightly higher risk in women. A history of frozen shoulder in the family is present in nearly 10% of cases.
It is still not clearly understood what causes frozen shoulder but we do know that the risk of getting it is increased in people with heart, pulmonary and neurological diseases as well as diabetes mellitus or a thyropathies.
Thyropathies is a term which refers to a group of thyroid diseases – hypothyroidism, hyperthyroidism, nodules and cancer. Someone with a thyropathy – especially if they have an underactive thyroid - has a 2.69 increased risk of developing frozen shoulder
Hypothyroidism and frozen shoulder
It is still not clearly understood what prompts the thickening of this connective tissue but we do know that there is a link between an underactive thyroid - like Hashimoto’s - and frozen shoulder
We also know that high levels of serum TSH are found both in hypothyroidism and in patients with a severe case of frozen shoulder
Several studies have been done on this. In one 401 shoulders were examined from 93 patients with frozen shoulder and 151 patients without frozen shoulder. There were a couple of interesting findings:
- There was significantly more diagnosed hypothyroidism in those with frozen shoulder
- The more severe the frozen shoulder the higher the TSH levels. This was particularly noticeable where patients had two frozen shoulders (bilateral frozen shoulder)
If you would like to a more detailed account of this study please click here
Hyperthyroidism and frozen shoulder
It is not uncommon for frozen shoulder to occur in patients with hyperthyroidism (overactive thyroid). Again, it is not clear what specifically causes this but it could be linked when an inflammatory process is stimulated by the production of cytokines. This is something which happens both in hyperthyroidism and frozen shoulder.
Cytokines are cell signalling proteins. The word comes from a combination of two Greek words “cyto” which means cell and “kinos” which means communication.
Hypothyroidism and Hyperthyroidism theory
Another theory about why both underactive and overactive thyroids are linked with frozen shoulder is that both conditions can cause muscle weakness.
The cause of this is not completely understood but it appears to be connected with the impact of thyroid hormone availability on the plasticity of the muscle to maintain the necessary speed of its contraction- relaxation cycle.
We also know that thyroid hormone signalling is needed for the development and regeneration of muscle. There are details about this here.
Do you have Bursitis or frozen shoulder?
Another common shoulder complaint is Bursitis and although those with a thyroid condition may be more prone to this, it is typically caused by repetitive over use of the shoulder (often due to sport or as an occupational requirement)
The main difference between the two conditions is when pain occurs. Pain occurs in Bursitis when you move the shoulder but in frozen shoulder the pain is there even when the shoulder is not in motion.
Like frozen shoulder, Bursitis (which also occurs in the elbow, knee, hip and ankle) can be caused by an underlying condition such as gout, rheumatoid arthritis, diabetes or thyroid disease
If you have frozen shoulder (or Bursitis) and some symptoms of hypothyroidism or hyperthyroidism it would be sensible to request a blood test from your GP who may not be aware of the potential link between thyroid conditions and frozen shoulder.
In some instances of Bursitis, treatment for a thyroid condition will also help the Bursitis
If you would like to read a recent paper from 2020 which discusses the evidence between frozen shoulder and thyroid diseases please click here:
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