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) have a tendency to run in families.
Hashimoto’s 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.
Thyroid cancers are of many kinds. One of these type is Medullary cancer, which can be seen in families.
Other thyroid diseases run in families too: silent thyroiditis, goiter, some other thyroid cancers for example. Sometimes, no specific cause can be found for thyroid problems (hypothyroidism in particular) – and even those cases seem to run in families.