Thyroid problems encompass a wide range of medical conditions. Some people produce too much thyroid, called hyperthyroidism, and others produce too little, which is called hypothyroidism. More than and less than normal production can be linked to a variety of factors, and two autoimmune diseases can severely affect thyroid production. People with Graves' disease may have hyperthyroidism, and those with Hashimoto thyroiditis may have hypothyroidism. Not all people with abnormal levels have one these diseases.

Answering the question as to whether thyroid problems are genetic is challenging. There is very little clear evidence or “gene” evidence, that thyroid problems are inherited, and in some instances, other things outside of the genes may cause problems with thyroid production. What is fairly clear is that thyroid problems do often occur in families, not just in human families, but also sometimes in certain dog breeds. Border collies, for instance, appear to have a higher rate of hypothyroidism.

What isn’t clear is whether anyone who inherits a predisposition for thyroid problems will necessarily have them. Some people with strongly family history don’t end up with problems and others with minimal family history do. Of course, there are plenty of people that have high or low thyroid levels and who never get tested or never pass on this information to family members. There is evidence that some people test slightly high or low but don’t get treatment.

Even with conditions like Graves' disease or Hashimoto thyroiditis, inheritance isn’t always clear cut. It isn’t unusual to see a whole family with Hashimoto thyroiditis, for example, a family of sisters. Whether each affected sister will pass this condition on to her children isn’t so obvious. The answer is that children may inherit the condition and may not. Yet since there seems to be links between thyroid problems and family history, it’s probably important to know if you have this history.

If you know your family has a history of thyroid problems, you should probably get checked to see if you have low or high levels of thyroid. People may need to be rechecked every year to two years to make sure they haven’t developed a problem with thyroid production. It’s also important to get checked after pregnancies because there is some link between deteriorating thyroid levels after pregnancy. Women over the age of 50 are most at risk for hypothyroidism and may develop it at a later age, even if they haven’t had problems in the past.