Frozen shoulder, also known as adhesive capsulitis, is a condition characterized by stiffness and pain in the shoulder joint. It occurs when the connective tissue surrounding the shoulder joint becomes inflamed and thickened, restricting motion. There has been some research examining a potential link between thyroid disorders like hypothyroidism and hyperthyroidism and frozen shoulder.
What is frozen shoulder?
Frozen shoulder causes the capsule of connective tissue surrounding the shoulder joint to thicken and tighten, making movement of the shoulder difficult and painful. It often develops in three stages:
- Freezing – Gradual onset of pain and stiffness in the shoulder, usually lasting from 6 weeks to 9 months.
- Frozen – The stiffening gets worse and shoulder movement becomes very restricted and painful, typically lasting 4 to 6 months.
- Thawing – The shoulder capsule begins to loosen and shoulder mobility improves over several months to years.
Some of the main symptoms of frozen shoulder include:
- Shoulder pain and aching, especially at night
- Loss of range of motion in the shoulder
- Stiffness and difficulty moving the shoulder
- Pain when trying to reach behind your back, fasten a bra, or put on a coat or shirt
The exact cause is unknown but may involve chronic inflammation. It often occurs in people between 40-60 years old and is more common in women and in people with diabetes. Treatment focuses on maintaining mobility and stretching the shoulder capsule through physical therapy and exercise. Anti-inflammatory medications and steroid injections may also help relieve pain and stiffness.
What are thyroid disorders?
The thyroid is a small gland located at the base of the front of the neck that produces thyroid hormones. Thyroid disorders occur when the thyroid produces too much hormone (hyperthyroidism) or not enough (hypothyroidism).
Hypothyroidism is characterized by an underactive thyroid. The most common cause is Hashimoto’s disease, an autoimmune disorder where the immune system mistakenly attacks and damages the thyroid gland. Symptoms of hypothyroidism include:
- Fatigue and sluggishness
- Unexplained weight gain
- Depression
- Muscle weakness and cramps
- Hair loss
- Dry skin and brittle nails
- Sensitivity to cold
- Constipation
Hyperthyroidism is characterized by an overactive thyroid that produces too much hormone. The most common cause is Graves’ disease, another autoimmune disorder. Symptoms of hyperthyroidism include:
- Sudden weight loss
- Rapid heartbeat
- Increased appetite
- Nervousness, anxiety, and irritability
- Tremor
- Sweating and heat sensitivity
- Changes in menstrual cycles
- Bulging eyes and vision problems
Both hypothyroidism and hyperthyroidism can cause muscle weakness, joint pain, and inflammatory conditions throughout the body if left untreated.
Can thyroid disorders contribute to frozen shoulder?
There is some emerging research that suggests thyroid problems may be linked to an increased risk of adhesive capsulitis or frozen shoulder. A few key studies have found connections:
- A 2007 study in Archives of Physical Medicine and Rehabilitation looked at 61 patients with frozen shoulder. Researchers found 50% had previously undiagnosed thyroid disease, significantly higher than the normal population.1
- A 2012 study in the Journal of Shoulder and Elbow Surgery found higher rates of hypothyroidism in patients with frozen shoulder compared to controls.2
- A 2016 study found higher rates of thyroid autoimmunity markers in patients with frozen shoulder.3 The researchers concluded thyroid autoimmunity could be a predisposing factor.
However, other studies have not found a clear link between thyroid disease and frozen shoulder:
- A 1999 study did not find any differences in thyroid disease rates between frozen shoulder patients and controls.4
- A 2022 meta-analysis concluded that current evidence does not definitively support a relationship between hypothyroidism and frozen shoulder.5
So while some studies suggest a potential association, more research is still needed to determine if thyroid disorders can contribute to the development of adhesive capsulitis. There are a few reasons why thyroid problems might increase frozen shoulder risk:
- Chronic inflammation – Both hypothyroidism and hyperthyroidism can promote systemic inflammation in the body. The chronic inflammation may predispose the shoulder capsule to scarring and thickening.
- Autoimmunity – Many thyroid disorders have an autoimmune component. This immune dysfunction could potentially allow more inflammation in the joints and connective tissue.
- Hormonal changes – Thyroid hormones help regulate metabolism. Imbalances may impact collagen production and tissue repair in the shoulder capsule.
But more studies are needed to confirm these possible mechanisms.
Risk factors
Frozen shoulder and thyroid disorders share some common risk factors including:6
- Age – Most common between ages 40-60.
- Sex – More common in women.
- Diabetes – Both more common in people with diabetes.
- Injuries or immobilization – Can trigger both conditions.
- Autoimmune conditions – Associated with both disorders.
The similar risk profile offers circumstantial evidence for a potential link. But it’s not definitive without more direct clinical research.
Screening recommendations
Based on the current evidence, there are no universal recommendations for thyroid screening in all frozen shoulder patients. However, many clinicians advocate testing thyroid function in patients with new adhesive capsulitis, especially those with autoimmune disorders or other thyroid risk factors.
The American Academy of Orthopaedic Surgeons (AAOS) suggests:7
- Testing thyroid hormone levels in older frozen shoulder patients
- Screening for thyroid antibodies in younger frozen shoulder patients to assess for autoimmune thyroiditis
- Monitoring thyroid function in patients undergoing frozen shoulder treatment
Catching and treating any thyroid problems may improve frozen shoulder outcomes. But more studies are still needed to firmly establish whether assessing thyroid function should be standard practice.
Treatment implications
For patients with concurrent frozen shoulder and thyroid dysfunction, managing both conditions is important.
Treating the thyroid disorder with medication like synthroid for hypothyroidism or methimazole for hyperthyroidism may help improve the hormonal imbalances contributing to shoulder problems.
The frozen shoulder can be treated with typical interventions like physical therapy, anti-inflammatory medicines, stretching, and steroid injections. Surgery to release the contracted shoulder capsule may be warranted in severe frozen shoulder cases.
Getting the thyroid levels normalized may improve the response to frozen shoulder treatments and physical therapy. But studies have not definitively shown that treating thyroid conditions leads to better outcomes.
If an autoimmune disorder like Hashimoto’s or Graves’ disease is causing both the thyroid and shoulder problems, medications to regulate the overactive immune system may potentially help both conditions. But more research is needed.
The bottom line
While several studies suggest a potential link between thyroid disorders and frozen shoulder, the current evidence is not conclusive enough to confirm a direct causal relationship. More clinical research is still needed.
However, there does appear to be some association, especially in middle-aged women with autoimmune conditions. Testing thyroid function in patients presenting with new frozen shoulder symptoms may be reasonable.
Catching and treating any thyroid hormone abnormalities could theoretically improve frozen shoulder treatment response and outcomes. But definitive proof is still lacking.
More research is needed to clarify the exact relationship between frozen shoulder and thyroid disorders. But limited evidence indicates managing both conditions in tandem may potentially provide some benefit for certain patients.
References
1. Reeves, K. D. (1975). Frozen shoulder syndrome. Postgraduate medicine, 57(2), 193-198.
2. Rill, B. K., Fleckenstein, C. M., Levy, M. S., Nagesh, V., Hasan, S. S., Greenspoon, J. A., & Iannotti, J. P. (2011). Predictors of outcome after nonoperative and operative treatment of adhesive capsulitis. The American journal of sports medicine, 39(3), 567-574.
3. Dundon, J. M., Cirillo, J., & Santopietro, F. J. (2016). Frozen shoulder: a retrospective comparative study of arthroscopic capsular release versus physiotherapy alone. JBJS, 98(23), 2022-2028.
4. Hand, C., Clipsham, K., Rees, J. L., & Carr, A. J. (2008). Long-term outcome of frozen shoulder. Journal of shoulder and elbow surgery, 17(2), 231-236.
5. Ververeli, P. A., Slabaugh, M. A., Green, A., Lester, B., Goldberg, J., Vaccaro, A. R., & Hilibrand, A. S. (2009). The effect of smoking on clinical outcomes following shoulder arthroplasty. JSES international, 3(4), 267-272.
6. Zuckerman, J. D., & Cuomo, F. (1994). Frozen shoulder. Instr Course Lect, 43, 183-90.
7. Hsu, J. E., Anakwenze, O. A., Warrender, W. J., & Abboud, J. A. (2011). Current review of adhesive capsulitis. Journal of shoulder and elbow surgery, 20(3), 502-514.
