Positive family history of thyroid disease as a risk factor for differentiated thyroid carcinoma

INTRODUCTION: Apart from the environmental risk factors for differentiated thyroid carcinoma (DTC), such as iodine deficiency and ionising radiation, it seems that there are also other, biological risk factors, for example, familial predisposition to thyroid disease. OBJECTIVES: The aim of the study was to assess the occurrence of thyroid disease in the families of patients with DTC. PATIENTS AND METHODS: A case‑control study was conducted in a group of 232 patients with DTC and in 342 age- and sex‑matched healthy subjects. Eighty patients were diagnosed with follicular thyroid carcinoma, 127 with papillary thyroid carcinoma, and 25 with oxyphilic thyroid carcinoma. The questionnaire included questions on the presence of thyroid diseases in first‑degree relatives. The relative risk of DTC and the effect of factors associated with thyroid diseases in the family were assessed by the logistic regression model. RESULTS: Thyroid disease was more common in the families of DTC patients than in the control group: 18.5% of the patients and 9.6% of the control group had a parent with thyroid disease (OR = 2.12, 95% CI: 1.26-3.55); 16.8% of the patients and 7.7% of the control group had a sibling with thyroid disease (OR = 2.27, 95% CI: 1.31-3.95). CONCLUSIONS: Familial thyroid disease may be a risk factor for DTC. A positive family history of thyroid disease is associated to a larger extent with the development of papillary thyroid carcinoma than with that of follicular thyroid carcinoma.