Frequency of abnormal thyroid function tests in Kuwaiti Arabs with autoimmune diseases

ABSTRACT

The purpose of this study was to examine the frequencies of abnormal thyroid function tests and serum thyroid autoantibodies in healthy Kuwaitis and those with autoimmune diseases. Serum concentrations of sensitive thyrotropin, and free thyroxine were measured in 577 apparently healthy controls, 177 patients with rheumatoid arthritis [RA], 60 with systemic lupus erythematosus [SLE] and 25 with primary Sjogren's syndrome [pSS] using the immunochemiluminescent assay method on IMMULITE 1000. Serum microsomal and thyroglobulin auto-antibodies were also measured by passive hemagglutination assay. For analysis of the thyroid function tests, the subjects were classified into five categories normal, sub-clinical hypothyroidism, overt hypothyroidism, euthyroid sick syndrome and biochemical hyperthyroidism. Subclinical hypothyroidism was seen in 1.7% of healthy controls, 10.2% of RA, 13.3% of SLE, and 16% of pSS patients. Among RA patients, the frequency of subclinical hypothyroidism in females [11.4%] was significantly higher than among males [5.4%; p < 0.01]. In SLE and pSS patients, all those with sub-clinical hypothyroidism were females. Overt hypothyroidism was seen in 1.4% of controls, 10.2% of RA, 8.3% of SLE, and 4% of pSS patients. Biochemical hyperthyroidism was seen in 0.2% of controls, 4.5% of RA, 5% of SLE and none of pSS patients. The euthyroid sick syndrome was seen in 0.4% of controls, 13.6% of RA, 16.7% of SLE and in none of pSS patients. Thyroid autoantibodies were present in 3.1% of controls, 12.4% of RA, 18.3% of SLE, and 12% of pSS patients. Our data show that abnormal thyroid function tests and thyroid autoantibodies occur frequently in Kuwaitis with autoimmune diseases. Therefore, ordering these tests in these diseases is recommended