It has been suggested that coeliac disease is associated with thyroid disease. Earlier studies, however, have been predominately cross-sectional and have often lacked controls.  In a recently published study, the risk of thyroid disease in individuals with coeliac disease was investigated from a general population cohort

A total of 14,021 individuals with coeliac disease (from 1964–2003) and a matched reference population of 68,068 individuals were identified through the Swedish national registers. Results showed coeliac disease is associated with thyroid disease, and these associations were seen regardless of temporal sequence. This indicates shared etiology and that these individuals are more susceptible to autoimmune disease.

Reference:  Elfström et al. 2008, Risk of Thyroid Disease in Individuals with Celiac Disease. Journal of Clinical Endocrinology and Metabolism. Vol 93, pp. 3915 - 3921.