Q. I was just wondering if you knew of any hereditary component to thyroid problems. Both my sister and I were diagnosed with hypothyroidism in high school and my dad was diagnosed with hyperthyroidism.
A. Yes, there is definitely a hereditary component to thyroid disease. Both the most common cause of hypothyroidism (Hashimoto’s) and the most common cause of hyperthyroidism (Graves) in the US have a tendency to run in families.
Hashimoto thyroiditis, an autoimmune disease characterized by gradual destruction of thyroid tissue, has a strong hereditary component. There is disease concordance in about 40% of monozygotic twins – and even asymptomatic siblings of affected patients often have circulating anti-thyroid antibodies! Certain polymorphisms in a couple genes in particular are associated with the development of Hashimoto disease; one is the cytotoxic T lymphocyte-associated antigen-4 (CTLA4) gene, and another is the protein tyrosine phosphatase-22 (PTPN2) gene. The CTLA4 gene product keeps a lid on T-cell responses; the PTPN22 gene product is a lymphoid tyrosine phosphatase that inhibits T-cell function. Other autoimmune diseases (like type 1 diabetes) are also associated with polymorphisms in these genes.
Graves disease, an autoimmune disease characterized by over-stimulation of the thyroid gland, also has a strong hereditary component. Its concordance rate in monozygotic twins is 30-40%. It is associated with the HLA-DR-3 allele, as well as the CLDA4 and PTPN2 genes mentioned above.
Other thyroid diseases run in families too: silent thyroiditis and goiter, for example. Sometimes, no specific cause can be found for thyroid problems (hypothyroidism in particular) – and even those cases seem to run in families.