INCREASED PREVALENCE OF THYROID AUTOANTIBODIES AND SUBCLINICAL THYROID FAILURE IN RELATIVES OF PATIENTS WITH OVERT ENDOCRINE DISEASE-ASSOCIATED DIABETES BUT NOT TYPE-1 DIABETES ALONE

The purpose of this study was to determine the prevalence of thyropero xidase (TPO) and thyroglobulin (Tg) antibodies, using a sensitive and specific radioimmunoassay method in a large cohort of 254 first-degree relatives of Type 1 diabetic patients with or with out other autoimmu ne endocrinopathy, and to evaluate the predictive value of thyroid ant ibodies for impaired thyroid function in these groups. TPO and Tg anti bodies were found at similar frequencies (12 %) in the 254 relatives, and both antibodies were present in 23 cases (9 %). Seven subjects dis played subclinical thyroid dysfunction without an abnormal free T4 lev el. Among first-degree relatives of probands with Type 1 diabetes alon e, TPO or Tg antibodies were found in 8 subjects (6 %), including 6 wi th both antibodies. The prevalence of TPO antibodies was significantly greater among relatives of TPO-positive than TPD-negative probands (p < 0.01). In relatives of diabetic patients with other endocrinopathy, frequencies of TPO (20 %), Tg (19 %) and a combination of both antibo dies (15 %) were significantly higher than in relatives of Type 1 diab etic patients without endocrinopathy (p < 0.001). TSH levels were abno rmal in only one relative of the group without endocrinopathy hut occu rred in 6 relatives of the proband with overt endocrinopathy-associate d diabetes (p < 0.02) in marked association with TPO antibodies (p < 1 0(-4)). It is concluded that relatives of probands with overt endocrin e autoimmune disease-associated diabetes, unlike those of probands wit h diabetes alone, showed increased prevalence of thyroid antibodies an d thyroid dysfunction. These results argue for a different risk of thy roid autoimmunity and clinical disease in families of diabetic patient s without or with overt endocrine disease. A screening of thyroid auto immunity is highly recommended for the latter group.