|Year : 2014 | Volume
| Issue : 2 | Page : 58-65
Hypothyroidism in patients with rheumatoid arthritis and its relation to disease activity
Enas A. Elattar1, Takwa B. Younes1, Sameh A. Mobasher2
1 Department of Physical Medicine, Rheumatology and Rehabilitation, Ain Shams University, Cairo, Egypt
2 Department of Internal Medicine, Faculty of Medicine, Ain Shams University, Cairo, Egypt
|Date of Submission||12-Aug-2013|
|Date of Acceptance||01-Nov-2013|
|Date of Web Publication||14-May-2014|
Enas A. Elattar
Department of Physical Medicine, Rheumatology and Rehabilitation, Faculty of Medicine, Ain Shams University, Cairo, Postal code: Cairo Elshorok city 11957
Source of Support: None, Conflict of Interest: None
Background and objective
The relationship between thyroid disease and rheumatic disorders has been the subject of considerable debate. Thyroid abnormal function and/or autoimmune thyroid disease were observed in patients with rheumatoid arthritis (RA), which could be attributed to the natural feature of autoimmune diseases and their tendency to overlap. Consideration of the fact that autoimmunity plays a role in the pathogenesis of both RA and hypothyroidism has raised the need to study the frequency of hypothyroidism and thyroid antibodies in RA patients and their relation to disease activity.
Patients and methods
One hundred and fifty RA patients and 50 control participants were included in this study. RA patients were subjected to a full assessment of medical and rheumatological history, and examination as well as routine lab tests. Patients and controls underwent thyroid function testing including thyroid antibodies. Patients' disease activity was determined using the Modified Disease Activity Score and their functional status was assessed using the Modified Health Assessment Questionnaire.
The most common thyroid dysfunction was hypothyroidism, which was found in 36 (24%) RA patients, followed by subclinical hypothyroidism in six (4%) patients, whereas subclinical hyperthyroidism was present in two (1.3%) patients. Autoimmune thyroid disease was present in 10 (6.6%) patients and absent in the controls. There was a significant positive correlation between thyroid stimulating hormone levels and RA disease activity parameters.
Hypothyroidism was the most common thyroid disorder associated with RA, present in 24%, with a significant association with RA disease activity parameters.
Keywords: autoimmune thyroid disease, hypothyroidism, rheumatoid arthritis, rheumatoid arthritis disease activity
|How to cite this article:|
Elattar EA, Younes TB, Mobasher SA. Hypothyroidism in patients with rheumatoid arthritis and its relation to disease activity. Egypt Rheumatol Rehabil 2014;41:58-65
|How to cite this URL:|
Elattar EA, Younes TB, Mobasher SA. Hypothyroidism in patients with rheumatoid arthritis and its relation to disease activity. Egypt Rheumatol Rehabil [serial online] 2014 [cited 2017 Oct 20];41:58-65. Available from: http://www.err.eg.net/text.asp?2014/41/2/58/132458
| Introduction|| |
Rheumatoid arthritis (RA) is a chronic autoimmune systemic inflammatory multisystem disease of unknown cause that may affect many tissues and organs, but principally attacks synovial joints, primarily affecting the peripheral joints in a symmetrical pattern . The pathology of the disease process often leads to destruction of articular cartilage .
RA affects ˜1% of the adult general population. Constitutional symptoms including fatigue, malaise, and morning stiffness are frequently experienced . Although the cause of RA is unknown, autoimmunity plays a pivotal role in both its chronicity and its progression through the high level of cytokines, especially the tumor necrosis factor α (TNF-α) .
Thyroid dysfunction may be broadly classified as hypothyroidism and hyperthyroidism. The most common cause of thyroid disorders worldwide is iodine deficiency, leading to goiter formation and hypothyroidism. However, in noniodine deficiency areas, the cause of hypothyroidism is either autoimmune (Hashimoto's thyroiditis), with a prevalence of 1-2%, and it is 10 times more common in women than in men , or hypothyroidism associated with the destructive treatment for thyrotoxicosis .
The relationship between thyroid dysfunction and RA has been a subject of debate, where several surveys suggested a relation between Hashimoto's thyroiditis and RA . Other studies showed that abnormal or changing thyroid status may precipitate or exacerbate musculoskeletal disease, especially when common features and symptoms for hypothyroidism such as fatigue, malaise, dyslipidemia, and increased weight could be masked by the original RA symptoms .
Moreover, thyroid dysfunction was observed at least three times more often in women with RA than women with similar demographic features with noninflammatory rheumatic diseases such as osteoarthritis and fibromyalgia . This was also confirmed in a more recent study in which thyroid abnormal function and/or autoimmune thyroid disease (AITD) was observed in 6-33.8% of patients with RA, which can be attributed to the natural feature of autoimmune diseases and their tendency to overlap . Frequent association with autoimmune diseases of other organs such as systemic lupus erythematosus , Sjogren's syndrome, scleroderma , and vasculitis  was observed.
Considering that autoimmunity plays a role in the pathogenesis of both RA and hypothyroidism through TNF-a, with the noticeable improvement in hypothyroidism in RA patients with anti-TNF-a treatment , this raised the need to study hypothyroidism and thyroid antibodies in RA patients and their relation to disease activity.
| Aim of the work|| |
To investigate the association of hypothyroidism and thyroid autoantibodies with RA and study their correlation with RA disease activity.
| Patients and methods|| |
Patients and controls
(1) The patient group included 150 adult RA Egyptian patients who presented to the outpatient clinics and were inpatients of the Rheumatology and Rehabilitation and Internal Medicine Departments of Ain Shams University Hospitals in the period from January 2012 to December 2012. These patients were either newly diagnosed according to the 2010 American College of Rheumatology (ACR)/EULAR RA classification criteria  or had been diagnosed previously according to the ACR revised criteria of RA 1987 .
Exclusion criteria were as follows:
- Patients on medication known to cause thyroid dysfunction (e.g. lithium, interferon alpha, etc.).
- Evidence of malignancy.
- Concurrent infection.
- Any collagen disease other than RA.
- Pregnant women.
- Chronic liver or renal diseases.
- Diabetic patients.
- Patients who had undergone thyroidectomy.
(2) The control group included 50 healthy individuals age and sex matched with the patient group.
The nature of our study was explained to all participants and a verbal consent was obtained. All patients were subjected to the following:
Assessment of medical and rheumatological history
Medical and rheumatological history was assessed with a special focus on symptoms of thyroid problems (e.g. palpitation, cold intolerance, weight gain, RA disease duration, morning stiffness, tender joints, swollen joints, etc.).
General and rheumatological examination
Careful general and musculoskeletal examination, thyroid gland examination, and calculation of BMI (weight in kg divided by the patient's height in m 2 ; ≥25 was considered abnormal) were performed. Waist circumference [an abnormal waist circumference was defined according to the International Diabetes Federation (IDF) for men as a circumference ≥94 cm and for women as ≥80 cm (http:www.idf.org/metabolic-syndrome) was measured. Medical treatment with methotrexate and/or prednisone was recorded including their current doses.
Assessment of disease activity was performed using the Modified Disease Activity Score (MDAS28) including 28 tender and swollen joint count scores, erythrocyte sedimentation rate (ESR), and the patient's subjective assessment (SA) of RA disease activity in the last 7 days recorded on a scale between 0 and 10, where 0 indicated 'no activity' and 10 indicated 'highest activity possible'. MDAS28 is calculated using the following formula :
The activity score of patients is graded as follows:
- A score of ≤2.6 was considered to indicate remission.
- >2.6 and ≤3.2 as low activity.
- >3.2 and ≤5.1 as moderate activity.
- >5.1 as high activity .
Rheumatoid arthritis functional status was assessed using the Modified Stanford Health Assessment Questionnaire
A questionnaire composed of eight questions on dressing, arising from bed, eating (or drinking), walking, self-hygiene, reaching objects, hand grip, and outside activities was used. One of four responses is recorded for each item: score 0 (without any difficulty), score 1 (with some difficulty), score 2 (with much difficulty), and score 3 (when unable to do). The mean of the total scores is the patient's score .
Routine laboratory investigations were performed including the following:
- Complete blood count using a Coulter JS (California, USA) cell counter.
- The ESR in the first hour, estimated using the Westergren method.
- Quantitative C-reactive protein (CRP) titer assessed using the immunoturbidimetric method.
- Kidney function tests (serum creatinine, blood urea nitrogen) were performed using the calorimetric method.
- Liver enzymes (ALT, AST) were assessed using the kinetic method.
- Fasting blood sugar and 2 h postprandial were determined.
- The lipid profile including total cholesterol, serum triglycerides, low-density lipoprotein (LDL), and high-density lipoprotein was assessed.
- Immunological assessment was performed for the rheumatoid factor (RF/IgM) that was measured using a Biotec (San Diego, USA, Genway Biotech) RA factor latex agglutination slide for the qualitative and semiquantitative determination of RF in the serum.
- Anti-cyclic-citrullinated peptide antibodies were assessed using an enzyme-linked immunosorbent assay. The cut-off value for the anti-cyclic-citrullinated peptide antibody was 5 U/ml .
Assessment of thyroid function was performed using the following:
- Thyroid stimulating hormone (TSH) was measured using immunometric assays (IMMULITE 2000 Third Generation; Diagnostic Products Corporation, Los Angeles, California, USA).
- Free serum triiodothyronin (FT3) level was determined using IMMULITE 2000 FT3, competitive, analog-based immunoassay for quantitative estimation of FT3 in serum on an IMMULITE 2000 system.
- Free serum thyroxin level (FT4) was measured using IMMULITE 2000 FT4, solid-phase chemiluminescent competitive immunoassay method for the quantitative determination of FT4 in serum on an IMMULITE 2000 system. Reference values were 0.27-4.2 IU/ml for TSH, 2.57-4.43 pg/ml for FT3, and 0.93-1.71 ng/dl for FT4 .
Clinical hypothyroidism and hyperthyroidism
Clinical hypothyroidism and hyperthyroidism were defined on the basis of the criteria of thyroid abnormalities as defined by the Dutch National Healthcare Consensus Committee :
Subclinical hypothyroidism: it was indicated by increased serum TSH in the presence of a normal serum FT4 level.
Clinical hypothyroidism: it was indicated by increased serum TSH with decreased serum FT4 level, at which stage most patients have symptoms and benefit from treatment.
Subclinical hyperthyroidism: it was indicated by normal serum FT4 and FT3 levels, with TSH levels below the normal range, usually undetectable.
Clinical hyperthyroidism: it was indicated by increased serum FT4 and FT3 levels, with TSH levels suppressed below the normal range, usually undetectable.
Antithyreoglobulin (anti-TG) antibodies and antithyroid peroxidase (anti-TPO) antibodies were assayed using an enzyme-linked immunosorbent assay method (Calbiotech Inc. California, USA). The reference values were less than 100 IU/ml for anti-TG antibodies and less than 50 IU/ml for anti-TPO .
The diagnosis of AITD was made on the basis of the presence of antithyroid antibodies (presence of increased anti-TPO antibodies levels) in patients with concomitant thyroid dysfunction and/or goiter. However, AITD was suspected if the values of anti-TPO antibodies were close to the reference range with increased levels of anti-TG .
Thyroid ultrasound was performed routinely at the Radiology Unit to indicate the need for a thyroid biopsy. However, biopsy was not performed as ultrasound did not show any indications such as cold nodules.
A thyroid scan was performed for the patients who showed subclinical hyperthyroidism (two patients and one control) using 99mTc radionucleid (g-rays emitters) and a gamma camera.
All data were collected, tabulated, and statistically analyzed.
Analysis of data was carried out by an IBM computer using statistical program for social science (SPSS) (software and services, North California, USA) version 18 as follows:
- Description of quantitative variables as mean, SD, and range.
- Description of qualitative variables as number and percentage.
- The χ2-test was used to compare groups in terms of qualitative variables.
- The Fisher exact test was used instead of χ2-test if one of the compared items (cell on excel) is less than digit 5.
- An unpaired t-test was used to compare two groups in terms of quantitative variable.
- P value more than 0.05 was considered insignificant, P value more than 0.05 was considered significant, and P value less than 0.001 was considered highly significant .
- Relationships between parameters were analyzed using the Pearson correlation coefficients (r).
| Results|| |
This study included 150 adult RA patients; 135 (90%) were women and 15 (10%) were men, and their ages ranged from 35 to 62 years (mean 45.2 ± 7.8 years), and a disease duration of 1-15 years (mean 7.7 ± 4.3 years). The study also included 50 age-matched and sex-matched controls; 45 (90%) were women and five (10%) were men, and their ages ranged from 38 to 60 years (mean 43.7 ± 9.3 years).
[Table 1] shows the descriptive data of patients and controls, with insignificant differences between both groups in age, sex, BMI, and waist circumference.
Cold intolerance was present in 15 (10%) patients, fatigue was present in 10 (6.6%), and palpitation in 12 (8%). Only three (6%) patients complained of palpitation. Clinical thyroid examination of patients indicated that 14 (9.3%) patients had multinodular goiter, 18 patients (12%) had diffuse goiter, and only two control participants (4%) had diffuse goiter.
|Table 1 Descriptive and demographic data of rheumatoid arthritis patients and the control group |
Click here to view
In terms of the disease activity of rheumatoid arthritis patients:
- 15 (10%) were in remission, DAS≤2.6.
- 45 (30%) had low disease activity, DAS < 2.6 and ≤3.2.
- 60 (40%) had moderate disease activity, DAS>3.2 and ≤5.1.
- 30 (20%) had high disease activity, DAS>5.1.
The Modified Health Assessment Questionnaire (MHAQ) score ranged from 4 to 15, with a mean value of 5.25 ± 3.7.
Laboratory data and thyroid function tests of patients and controls
There were highly significant differences between both groups in ESR (P < 0.00), CRP (P < 0.00), and LDL (P < 0.00), as well as significant differences in the levels of TSH (P < 0.05), anti-TPO antibodies (P < 0.05), and anti-Tg antibodies (P < 0.05) [Table 2].
Of the 150 RA patients studied, laboratory thyroid abnormalities were present in 44 (29.3%) patients versus four (8%) control participants [Table 3].
- Hypothyroidism was the most common disorder found in 36 (24%) patients versus one (2%) control participant.
- Subclinical hypothyroidism was found in six (4%) patients versus two (4%) control participants.
- Subclinical hyperthyroidism was found in two (1.3%) patients versus one (2%) control participant.
- None of the patients or the controls had hyperthyroidism.
|Table 2 Comparisons between patients and controls in laboratory and thyroid function data |
Click here to view
|Table 3 Frequency of thyroid abnormalities among rheumatoid arthritis patients and controls |
Click here to view
Classification of rheumatoid arthritis hypothyroid patients (n = 36) according to their activity state
On classifying one (0.06%) patient was found to be in an inactive state, four (2.6%) in a mild activity state, 25 (16.6%) in a moderate activity state, and six (4%) in a severe activity state.
According to the (laboratory thyroid functions) , patients were subdivided into two groups: 114 (76%) patients were either normal or had a subclinical thyroid state (group A), whereas 36 (24%) patients were in a hypothyroid state (group B).
On comparing the demographic data between 114 (76%) patients with normal or subclinical thyroid disorders (group A) and 36 (24%) patients in a hypothyroid state (group B), there were significant differences in disease duration (P < 0.05), BMI (P < 0.00), waist circumference (P < 0.00), disease activity (P < 0.05), and MHAQ (P < 0.05). In addition, there were significant laboratory differences in ESR (P < 0.05), levels of cholesterol (P < 0.05), TG (P < 0.05), LDL (P < 0.05), anti-TPO (P < 0.05), and anti-Tg (P < 0.05) antibodies. Highly significant differences were present in TSH (P < 0.001), FT3 (P < 0.001), and FT4 (P < 0.001).
Current prednisone used (daily dose) and methotrexate (weekly dose) were higher in group B than in group A, with a significant difference (P < 0.05) [Table 4].
|Table 4 Comparison between demographic and laboratory data of rheumatoid arthritis patients (group A) and rheumatoid arthritis patients with hypothyroidism (group B) |
Click here to view
Anti-TPO antibodies were present in 14 (9.3%) RA patients, whereas anti-Tg antibodies were present in five (3.3%) RA patients compared with three (6%) and one (2%) control participants, respectively, with no statistical difference (P > 0.05) between both groups.
Accordingly, AITD was considered positive in 10 (6.6%) patients who showed hypothyroidism together with positive anti-TPO antibodies that was not observed in any of the controls.
On correlating between TSH levels and the RA disease activity parameters, there were significant positive correlations with (ESR, MDAS28, MHAQ, and dose of methotrexate) [r = 0.783 (P < 0.02), r = 0.888 (P < 0.01), r = 0.854 (P < 0.01), and r = 0.7454 (P < 0.03), respectively].
Significant positive correlations were also found between TSH levels and BMI, waist circumference, and TG [r = 0.75 (P < 0.32), r = 0.83 (P < 0.019), and r = 0.67 (P < 0.049), respectively].
However, the levels of FT3 showed significant negative correlations with the RA disease activity parameters: ESR (r = -0.76, P < 0.01), MDAS28 (r = -0.87, P < 0.01), MHAQ (r = 0.79, P < 0.03), and dose of methotrexate (r = -0.084, P < 0.012) as well as significant negative correlations between FT3 levels and BMI (r = -0.78, P < 0.031), waist circumference (r = -0.80, P < 0.024), and TG (r = -0.70, P < 0.036) [Table 5].
|Table 5 Correlations of levels of thyroid stimulating hormone and free T3 with disease duration, activity score, BMI, cholesterol, thyreoglobulin levels, and drug intake in rheumatoid arthritis patients |
Click here to view
| Discussion|| |
The coexistence of thyroid dysfunction/thyroiditis and RA has been a subject of debate . Some workers have suggested that hypothyroidism might exacerbate rheumatoid disease with a destructive arthropathy affecting mainly the proximal interphalangeal joints ,, associated with fatigue, anemia, and myalgia, all attributed to the inflammatory state of RA .
This study was designed to investigate the association of hypothyroidism and thyroid autoantibodies with RA and to study their correlation with RA disease activity. The study included 150 adult RA patients, 135 (90%) women and 15 (10%) men.
Thyroid abnormalities were present in 44 (29.3%) RA patients and four (8%) control participants, which is not in agreement with the study of Shiroky et al. , who found that 29 (30%) RA patients had evidence of thyroid dysfunction compared with 10 (11%) of their controls, although another Egyptian study has reported less frequent thyroid dysfunction (8.3%) .
Hypothyroidism was the most common disorder in our study, found in 36 (24%) patients, similar to other authors who showed that clinical hypothyroidism was the most common thyroid disorder associated with RA [9, 11, 23, 24].
Clinical hypothyroidism was observed three times more often in RA female patients than in women of the general population [9,25]. In our study, 31 (20%) female RA patients compared with five (4%) men had hypothyroidism.
Anti-TPO and anti-Tg antibodies were present in 14 and five of our RA patients (9.3 and 3.3%, respectively), with insignificant differences from the controls (P > 0.05). These results are almost in agreement with the results of Mousa et al. , who found positive anti-TPO and anti-Tg antibodies in 10 and 6% of Egyptian RA patients. However, our data were different from those of other populations, where these antibodies were present in 15.9 and 12.3% of Turkish RA patients . Also, a higher percentage of thyroid antibodies was recorded in Polish RA patients (15 and 12%, respectively)  as well as in Colombian RA patients (37.8 and 20.8%) . These variations in the percentage of antithyroid antibodies can be attributed to ethnic and environmental differences of the studied populations.
Fewer studies have studied the relationship of the AITD with RA disease activity .
AITD was considered positive in 10 (6.6%) RA patients, which was almost in agreement with the results of other studies that found a prevalence of AITD in 9.8% of their studied RA patients; however, others have found a higher prevalence of 16% in their RA patients .
Common etiological factors for RA and hypothyroidism have been discussed such as the use of salicylates and many other NSAIDs or corticosteroids in treating RA, which have been shown to alter thyroid gland function ,,. Therefore, the pathogenesis of thyroid disease in patients with RA may have a common pathway and it was speculated that thyroid disorders are the result of the antithyroid activity of one of the antibodies produced in RA . Moreover, a genetic predisposition determined by a certain Human Leucocyte Antigen (HLA) type, most often HLA-DR, is one possible explanation for the presence of two or more autoimmune diseases in one individual . More explanations have been suggested when anti-TNF-α treatment improved thyroid function in hypothyroid patients with RA , also provided evidence that inflammatory cytokines may play a pathogenic role in thyroid dysfunction .
Our results showed positive significant correlations between serum levels of TSH and RA activity parameters (ESR, MDAS28, MHAQ, and dose of methotrexate), indicating that higher levels of TSH are associated with higher grades of RA disease activity. Also, we found negative significant correlations between serum levels of FT3 and RA activity parameters (ESR, MDAS28, MHAQ, and dose of methotrexate), indicating that lower levels of FT3 are linked to higher grades of RA disease activity.
Some authors found that hypothyroidism correlated with the number of swollen joints in RA patients , whereas others found higher levels of CRP in RA patients with hypothyroidism , which is in contrast to our results. However, other studies could not find a correlation between hypothyroidism and RA disease activity state , and concluded that thyroid hormonal defects were related to the disease duration and not the disease activity, although it is inconsistent with our results; this could be because of the short mean duration of our RA (7.7 ± 4.3 years) compared with theirs.
| Conclusion|| |
Thyroid dysfunction and AITD are common in RA patients, with hypothyroidism being the most common disorder prevalent in 24% of patients. TSH and FT3 have shown an evident correlation with RA disease activity as well as clinical and laboratory disease parameters.
- Thyroid function and antithyroid antibodies tests should be performed as part of the biochemical and immunological profile in RA patients.
- Treatment of both clinical and subclinical hypothyroidism should be considered in RA patients.
- Clinical follow-up is needed to clarify the effect of thyroid dysfunction treatment on RA activity and vice versa.
| Acknowledgements|| |
| References|| |
|1.||Howard R, Kristine M, Francisco T, Elliot G, Alex JM, Herbert S. Rheumatoid arthritis. e.Medicine 2006; www.mdguidelines.com/arthritis-rheumat Medical Disability Guidelines. 24 may 2006; Medscape. |
|2.|| Raterman H, Jamnitski A, Lems W, Voskuyl A, Dijkmans B, Bos W, et al. Improvement of thyroid function in hypothyroid patients with rheumatoid arthritis after 6 months of adalimumab treatment; a pilot study. J Rheumatol 2011; 38:247-251. |
|3.|| Tunbridge W, Evered D, Hal R, Appleton D, Brewis M, Clark F, et al. The spectrum of thyroid diseases in the community: the Whickham survey. Clin Endocrinol (Oxf) 1977; 7:481-491. |
|4.|| Vanderpump M, Tunbridge W. Epidemiology and prevention of clinical and subclinical hypothyroidism. Thyroid 2002; 12:837-847. |
|5.|| Tunbridge W, Vanderpump MP. Population screening for autoimmune thyroid disease. Endocrinol Metab Clin North Am 2000; 29:239-253. |
|6.|| Porkodi R, Ramesh S, Mahesh A, Kanakarani P, Rukmangathrajan S, Panchapakesa C. Thyroid dysfunction in systemic lupus erythematosus and rheumatoid arthritis. J Indian Rheumatol Assoc 2004; 12:0-0. |
|7.|| Shiroky J, Cohen M, Ballachey M, Neville C. Thyroid dysfunction in rheumatoid arthritis; a controlled prospective survey. Ann Rheum Dis 1993; 52:454-456. |
|8.|| Przygodzka M, Filipowicz-Sosnowska A. Prevalence of thyroid diseases and ant thyroid antibodies in women with rheumatoid arthritis. Pol Arch Med Wewn 2009; 119:39-43. |
|9.|| Raterman H, Vn Halm V, Voskuyl A, Simsek S, Dijkmans B, Nurmohamed M. Rheumatoid arthritis is associated with a high prevalence of hypothyroidism that amplifies its cardiovascular risk. Ann Rheum Dis 2008; 67:229-232. |
|10.||Haghighi A. Prevalence of thyroid disorders in systemic lupus erythematosus and rheumatoid arthritis. Iran J Endocrinol Metab 2009; 11(1):49-55. |
|11.||Mousa A, Ghonem m, Hegazy A, El Biomy A, El-diasty A. Thyroid function and auto-antibodies in Egyptian patients with systemic lupus erythemaosus and rheumatoid arthritis. Trends Med Res 2012; 7:25-33. |
|12.||Arnett F, Edworthy S, Bloch D, Mc Shane D, Fries J, Cooper N, et al. The American Rheumatism Association 1987 revised criteria for the classification of rheumatoid arthritis. Arthritis Rheum 1988; 31:315-324. |
|13.||Aletaha D, Neogi T, Silman A, Funovits J, Felson D, Bingham III C, et al. 2010 rheumatoid arthritis classification criteria: an American College of Rheumatology/European League against Rheumatism collaborative initiative. Ann Rheum Dis 2010; 69:1580-1588. |
|14.||Prevoo M, Van't Hof M, Kuper H, Van Leeuwen M, Van Deputte L, Van Riel P. Modified Disease Activity scores that include twenty-eight joint counts. Development and validation in a prospective longitudinal study of patients with rheumatoid arthritis. Arthritis Rheum 1995; 38:44-48. |
|15.||Aletaha D, Smolen J. The Simplified Disease Activity Index (SDAI) and the Clinical Disease Activity Index (CDAI): a review of their usefulness and validity in rheumatoid arthritis. Clin Exp Rheumatol 2005; 23:S100-S108. |
|16.||Pincus T, Summey J Soraci S Jr, Wallston K, Hummon N. Assessment of patients satisfaction in activities of daily living using a Modified Stanford Health Assessment Questionnaire. Arthritis Rheum 1983; 26:1346-1353. |
|17.||Kim S, Bae J, Lee H, Kim J, Park S, Choe J. Greater prevalence of seropositivity for anti-cyclic citrullinated peptide antibody in unaffected first-degree relatives in multicase rheumatoid arthritis-affected families. Korean J Intern Med 2013; 28:45-53. |
|18.||Miller C, Knapp RG. Clinical epidemiology and biostatistics. 3rd ed.. Maryland: Williams &Wilkins; 1992. |
|19.||Delamere J, Scott D, Felix-Davies D. Thyroid dysfunction and rheumatic diseases. J R Soc Med 1982; 75:102-106. |
|20.||Arnaout M, Nasrallah N, El-Khateed M. Prevalence of abnormal thyroid function tests in connective tissue disease. Scand J Rheumatol 1994; 23:128-132. |
|21.||Surks I, Sievert R. Drugs and thyroid functions. N Eng J Med 1995; 333:1688-1695. |
|22.||Punzi L, Betterle C. Chronic autoimmune thyroiditis and rheumatic manifestations. Joint Bone Spine 2004; 71:275-283. |
|23.||El-Sherief W, El-Gendi M, Ashmawy H, Salama M. Thyroid disorders and autoantibodies in systemic lupus erythematosus and rheumatoid arthritis. Egypt J Immunol 2004; 11:81-90. |
|24.||Chan A, Al Saffar Z, Buchnall R. Thyroid disease in systemic lupus erythematosus and rheumatoid arthritis. Rheumatology 2001; 40:353-354. |
|25.||Chandankhede M, Gupta M, Chandankhede S, Chari S. Thyroid profile in female patients with rheumatoid arthritis. J Recent Adv Appl Sci 2011; 26:34-36. |
|26.||Yavasoglu I, Senturk T, Coskun A, Bolaman Z. Rheumatoid arthritis and anti-thyroid antibodies. Autoimmunity 2009; 42:168-169. |
|27.||Cárdenas Roldán J, Amaya-Amaya J, Castellanos-de la Hoz J, Giraldo-Villamil J, Montoya-Ortiz G, Cruz-Tapias P, et al. Autoimmune thyroid disease in rheumatoid arthritis: a global perspective. Arthritis 2012; 2012:864907. |
|28.||Arnett F, Edworthy S, Bloch D, McShane D, Fries J, Cooper N, et al. The American Rheumatism Association revised criteria for the classification of rheumatoid arthritis. Arthritis Rheum 1987; 31:315-324. |
|29.||Ilias I, Mastorakos G, Mavrikakis M, et al. Thyroid disease associated with rheumatoid arthritis is not adequately screened with a sensitive chemiluminescence thyrotropin assay. Acta Med Austraica 1999; 26:26-28. |
|30.||Staykova N. Rheumatoid arthritis and thyroid abnormalities. Folia Med (Plovdiv) 2007; 49:5-12. |
|31.||Tarhan F, Oruk G, Niflioglu O, Ozer S. Thyroid involvement in ankylosing spondylitis and relationship of thyroid dysfunction with anti-TNF-α treatment. Rheumatol Int 2013; 33:853-857. |
|32.||Singh B, Mittal B, Bhattacharya A, Deodhar S. A cross sectional evaluation of circulating thyroid hormonal profile in patients with rheumatoid arthritis. IJNM 2002; 17:68-72. |
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]