PHOENIX — Family history of thyroid disease and a lower median age at diagnosis were significantly associated with illness in a study of 2,805 adults with thyroid disease, researchers reported in a poster presented at the annual meeting of the American Thyroid Association.
To assess the genetic and environmental factors that impact thyroid disease, Dr. N. Manji of the University of Birmingham (England) and colleagues reviewed data from 2,405 patients with Graves' disease (GD) and 400 patients with Hashimoto's thyroiditis (HT).
Overall, 957 GD patients and 223 HT patients reported a family history of thyroid dysfunction. GD patients who reported a parent with thyroid dysfunction were significantly younger than patients who did not report a family history when their disease was diagnosed (38 years vs. 43 years); the same was true for HT patients (39 years vs. 47 years). Among the GD patients, a younger age at diagnosis was independently associated with more severe disease and the presence of a palpable goiter.
Of note, GD patients were significantly more likely to have a relative with hyperthyroidism than with hypothyroidism (30% vs. 24%), while HT patients were significantly more likely to have a relative with hypothyroidism than with hyperthyroidism (42% vs. 23%). This finding supports recent data that have suggested a disease-specific genetic effect within the spectrum of autoimmune disease, the researchers noted.
Patients reported a family history of thyroid disease in a maternal relative significantly more often than in a paternal relative, regardless of whether they had GD or HT. In addition, smoking and having a higher serum-free T4 level at the time of thyroid disease diagnosis were significant independent predictors of ophthalmopathy. Additional studies of the interactions between genetic and environmental factors in thyroid disease could help prevent disease and develop customized therapies, the researchers noted.
Complete results of the study appeared in a recent issue of the Journal of Clinical Endocrinology and Metabolism (J. Clin. Endocrin. Metab. 2006 Sept. 12 [Epub doi:10.1210/jc.2006-1402]).