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You have probably heard that some medical conditions are hereditary, meaning they can run in your family. Research suggests that thyroid conditions such as cancer and Hashimoto’s have a genetic component associated with them. But that doesn’t mean that is the only factor contributing to their development.
Below, we explore the genetic component and the role it can play in the development of thyroid cancer and Hashimoto’s.
Your thyroid, a small, butterfly-shaped gland, sits at the base of your neck behind the Adam’s apple. Two types of cells, each with different functions, make up your thyroid gland.
- Follicular cells make thyroid hormones, T4 (thyroxine) and T3 (triiodothyronine), by using iodine from your blood
- Parafollicular cells, also called C-cells, make a hormone called calcitonin that controls how your body uses calcium
A change in how either of these thyroid cells functions can result in significant changes in your body. For instance, if your follicular cells make too little thyroid hormone, you may develop hypothyroidism. In contrast, when follicular cells make too much thyroid hormone, you are at risk for hyperthyroidism.
An abnormal production of a specific type of cell in your body is the driving force that causes cancer in the thyroid gland. In this case, it is an abnormal production of one type of thyroid cell. It is essential to know what cells are affected as that helps determine the severity of thyroid cancer and the treatment course.
There are three types of thyroid cancer:
- Differentiated thyroid cancers (DTC): There are three subtypes of DTC: papillary, follicular, and Hurthle cell. All three of these subtypes start in your follicular cells. Papillary thyroid cancer is the most common, accounting for 80% of diagnoses. Follicular cancer is the next most common type, with an estimated 10% of thyroid cancers being this type. Lastly, Hurthle cell cancer is rare, making up 3% of thyroid cancer diagnoses.
- Medullary thyroid cancer (MTC): MTC accounts for 4% of all thyroid cancers and develops in your parafollicular cells. There are two types of MTC: sporadic and familial. Sporadic MTC is more common than familial MTC, making up 80% of MTC cases.
- Anaplastic thyroid cancer: A rare form of thyroid cancer that may develop from an existing follicular or papillary cancer. It accounts for 2% of thyroid cancer cases.
Over 90% of thyroid cancers are sporadic and arise from random changes to your genes. The remaining 10% are familial forms, meaning thyroid cancer genes are passed down from generation to generation through genes.
For instance, sporadic MTC- not hereditary- is more common than familial MTC.
Besides your genes, other factors can contribute to your risk of developing thyroid cancer:
- Exposure to radiation of your head and neck during childhood
- Being overweight or obese
- Excessive iodine in the diet
- Family history of non-inherited thyroid cancer in a parent, sibling, or child
- Gender, with women at greater risk
Hashimoto’s thyroiditis is an autoimmune disorder where the immune system produces antibodies that attack and destroy your thyroid follicular cells. Because of this destruction, your follicular cells can’t make enough thyroid hormone to support your body’s needs. When this occurs, cells throughout your body won’t function correctly, resulting in an underactive thyroid, and symptoms of hypothyroidism such as:
Hashimoto’s is the number one cause of hypothyroidism. Yet, what triggers the destruction of your follicular cells is unknown. Besides genetics, environmental factors may include:
- Iodine intake
- Alcohol intake
- Prescription medications
- Deficiency in specific essential vitamins and minerals
The genetic link with Hashimoto’s isn’t as clear-cut as with thyroid cancer.
People with Hashimoto’s have thyroid antibodies against Thyroid Peroxidase (TPO) and thyroglobulin (TG). Antibodies are your immune system’s way of quickly identifying and destroying foreign invaders. Since the immune system thinks your follicular cells are invaders, it will produce antibodies against them.
When both parents have autoimmune thyroid disease, TPO and TG antibodies are higher in their children, especially their daughters. It makes sense, as women are up to 10 times more likely than men to develop Hashimoto’s. In contrast, when only one parent has thyroid antibodies, their children are less likely to have them.
But there also appears to be a sibling link. More than half of those with thyroid autoantibodies have a sibling with an autoimmune thyroid disease. Therefore, the risk of developing Hashimoto’s increases when you have a parent or sibling with it. Based on 2020 study findings, having a sibling with Hashimoto’s puts you at a much greater risk of developing it than having a parent with Hashimoto’s.
The same 2020 study also reported that among those with Hashimoto’s, about 5% had a first-degree relative that also had it. The familial risk for inheriting the same set of genes was higher for those with Hashimoto’s compared to Graves’ disease, another autoimmune thyroid disorder.
Interestingly, that same study showed men were more likely than women to have a familial risk for developing Hashimoto’s. Since women overall are more likely to develop Hashimoto’s, this evidence shows that genetics play a role, but so do external factors.
Even though both thyroid cancer and Hashimoto’s have a genetic component, having a family history of either medical condition doesn’t mean you will develop it. Other risk factors, including environmental ones, also play a role in developing either medical condition.
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You can start your thyroid evaluation by checking your thyroid hormone levels. In the past, this involved going to the lab and having your blood drawn. But, with Paloma’s at-home testing kit, you can skip the lab visit. Our testing kit only requires a finger prick blood sample and measures four thyroid biomarkers: thyroid-stimulating hormone (TSH), free thyroxine (Free T4) and free triiodothyronine (Free T3), and TPO.
Your results, along with a detailed interpretation, are accessible through our portal within a week. Paloma Health has an array of thyroid specialists that can help you further understand your results, develop a treatment plan, or continue to monitor and treat you if you have an underactive thyroid. (Please note that Paloma’s thyroid providers do not treat thyroid cancer.)