Association between Frozen Shoulder and Thyroid Diseases: Strengthening the Evidences

Objective To clarify the association of thyroid disorders and primary frozen shoulder by comparing this group with controls without shoulder disease and with patients with rotator cuff tears. Methods We evaluated 166 patients who presented frozen shoulder with treatment in progress or already treated, which were compared with 129 patients with diagnosis of rotator cuff tears and 251 control subjects. All of the participants answered the questionnaire on the following variables: age, gender, body mass index (BMI), occupation, physical activity, presence of thyroid disorders and other comorbidities, smoking and use of alcohol. Results When comparing the frozen shoulder group with the control and rotator cuff groups, there is a specific association between the presence of thyroid disorders and frozen shoulder. By calculating relative risk, it is possible to state that an individual with thyropathy has 2.69 more chance of developing frozen shoulder. Also, there was an association with gender, since women with frozen shoulder exceeded significantly the risk. Conclusions Thyroid disorders, especially hypothyroidism and the presence of benign thyroid nodules, are risk factors significantly associated with frozen shoulder, rising the chances to 2.69 times of developing frozen shoulder. This is the first study that uses, in addition to the control group, a second group with rotator cuff tears, so it was shown that there is a specific association of thyroid disorders and frozen shoulder, but not with shoulder disorders in general.