Thyroid Peroxidase (Tpo) Antibodies And Thyroid Dysfunction In Rheumatoid Arthritis: A New Dimension In The Relationship
Main Author: Haider M Al Attia
Abu Dhabi United Arab Emirates
Private Sector Clinic
Objective(s):
Rheumatoid arthritis (RA) and autoimmune thyroid disease may co-exist. The relation however, between the antibodies of the RA and thyroid antibodies was found to be variable in different studied populations yet remained of high interest to clinicians of concern.
Method(s): 110 adult patients with RA and residents of Abu Dhabi , UAE, underwent assays for anti thyroid peroxidase antibodies (anti-TPO Abs) , thyroid function test ( FT3, FT4& TSH) in addition to rheumatoid factor (IgG), and anti cyclic citrullinated peptide( anti CCP anti bodies) .
Results:
54 (49% ) were individuals from various Arab states and 44 (40)% were Asians from the Indian subcontinent. The rest (11% ) were individuals from Europe, south East Asia and Africa. Their age ranged from 20-74 years with a mean of 45.2 +/-12.6 and of a mean disease duration of 4.72 +/- 5.22 years. The F: M ratio was 2.25:1 ( 76: 34). Rheumatoid seropositivity was based on the presence of RF alone, Anti CCP alone or the combination of both sero markers. 83 patients (75.5%) were seropositive . The seropositive patients were significantly older (49.9 +/-12) than the seronegative (39.9+/-12.9 years) , P=0.011 while the disease duration was not different (4.72 +/-5.2 vs, 4.07 +/- 4.24 years) in the seropositive and seronegative patients respectively, P=0.57.
23 patients (21%) were TPO Abs positive , 18 in the seropositive (21.5%) and 5 (18.5%) in negative patients respectively, P=1.000.
In the seropositive subgroup , the clustering of TPO Abs positivity was higher in those with combined seropositivity (RF plus Anti CCP Abs) 14/18 (77.5%), than that in each of the patients with positive RF alone (2/18,11%) or with positive anti CCP Abs alone(2/18, 11%), P=0.002 if compared collectively or individually, P=0.0001.
The TPO titer was 211+/-168 ( 38.1-600 units/ml) in the seropositive patients vs,190+/-231 (65-600 units/ml) in seronegative, P=0.82. Based on a high titer cut off reading of 200 units or more of anti TPO titer which is consistent with Hashimoto’s thyroiditis ,a 7/18 (39%) in seropositive patients and one (20%) in the other group had higher levels ,P=NS.
None , had hyperthyroidism in the entire group. Hypothyroidism was found in 13 patients (12%), 10/83 (12%) in seropositive and 3 /27 in seronegative patients (11%), P=1.000 emphasizing the independence of hypo functioning thyroid disease from the rheumatoid seropositivity.
Conclusion(s):
Obviously, the anti TPO Abs in RA patients appeared to occur independently of the seropositivity of the disease. Their higher and significant association with the combined seropositivity in this group of patients can be considered as a new finding with regard to the autoimmunity of rheumatoid arthritis. Hypothyroidism was infrequent in these patients and had occurred irrespective to the presence of anti TPO Abs and RA seropositivity. Overall , the result here add up to the diversity of the serological profiles of these antibodies in different populations with rheumatoid arthritis.
