Thyroid disease is surprisingly common. Studies have estimated that around 1 in 20 people in the U.S. have hypothyroidism or hyperthyroidism, some of the most common thyroid conditions.[1,2] Yet despite how prevalent thyroid disease is, it’s also frequently missed. According to the American Thyroid Association, up to 60% of people with a thyroid condition are unaware of it.[3]
Thyroid 101
The thyroid is a butterfly-shaped organ in the neck, just in front of the trachea, that despite its small size plays an important role in a range of physiological functions. It produces thyroid hormone, which circulates throughout the body and impacts metabolism, energy levels, and more. If the thyroid is underactive (hypothyroidism), it doesn’t produce enough thyroid hormone. Conversely, if it’s overactive (hyperthyroidism), it produces too much.
The most common causes of both conditions are autoimmune disorders,[4] where the body’s immune system mistakenly attacks cells in the thyroid.
What makes thyroid diseases difficult to diagnose?
One factor is that symptoms can be non-specific. With autoimmune hypothyroidism, for instance, symptoms can include things like weight gain, low energy, joint stiffness, and depression — which can easily be mistaken as the result of stress or too much time behind a computer, for example. Plus, symptoms can come on gradually over time. Or symptoms may come and go.
Sometimes it’s more than just stress
A common scenario for someone with undiagnosed Hashimoto’s: you start to notice gradual but unexplained weight gain along with unshakeable fatigue, and decide to double down on diet and exercise. Yet you see little impact of these efforts. That’s such a common experience — even for those with normal thyroid function — that it might not occur to you, or your doctor, to get a blood test to rule out potential thyroid problems.
The good news is that once they’re diagnosed, both hypothyroidism and its counterpart, hyperthyroidism, are treatable, though they may demand lifelong attention to managing them.
Exploring the role of genetics
Like other autoimmune conditions, Hashimoto’s disease and autoimmune hyperthyroidism (Graves’ disease) have a strong genetic component. It’s been observed that individuals have a “set point” or characteristic level of thyroid hormone,[5] and genetics may explain up to two-thirds of the variation between individuals in this set point.[6]
So could genetics help identify people more likely to experience thyroid conditions? In recent years, research has explored how genetics can be used to predict risk for diseases like Hashimoto’s using polygenic risk scores, or PRS. Someone with the highest genetic likelihood for Hashimoto’s disease based on a PRS calculated by 23andMe has a 3-6 times higher odds of being diagnosed with this condition than someone with an average genetic likelihood.[7]
Polygenic scores also have promising applications for predicting risk of thyroid cancer, predicting subtypes of thyroid cancer, and even improving AI tools for predicting which thyroid nodules are malignant.
And genomics can help tease apart the biological mechanisms of thyroid function that underlie all these conditions.
Genetics as a tool for awareness and early action
Genetic insights can reveal an increased susceptibility to thyroid conditions, empowering individuals to be more proactive about their health. This heightened awareness could pave the way for faster diagnoses and earlier treatments. And that translates to more years of good health.
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References:
[1]Doubleday AR et al. (2020). “Hyperthyroidism.” Gland Surg. 9(1):124-135. https://pubmed.ncbi.nlm.nih.gov/32206604/
[2]Patil N et al. (2024). “Hypothyroidism”. StatPearls [Internet]. Accessed May 19, 2025, from https://www.ncbi.nlm.nih.gov/books/NBK519536/.
[3]American Thyroid Association. “General Information/Press Room.” Accessed May 19, 2025, from https://www.thyroid.org/media-main/press-room/.
[4]Vanderpump MP. (2011). “The epidemiology of thyroid disease.” Br Med Bull. 99:39-51. https://pubmed.ncbi.nlm.nih.gov/21893493/
[5]Andersen S et al. (2002). “Narrow individual variations in serum T(4) and T(3) in normal subjects: a clue to the understanding of subclinical thyroid disease.” J Clin Endocrinol Metab. 87(3):1068-72. https://pubmed.ncbi.nlm.nih.gov/11889165/
[6]Panicker V. (2011). “Genetics of thyroid function and disease.” Clin Biochem Rev. 32(4):165-75. https://pubmed.ncbi.nlm.nih.gov/22147956/
[7]Ashenhurst JR et al. (2025). “White Paper 23-21: A generalized method for the creation and evaluation of polygenic scores.” 23andMe. Accessed May 19, 2025, from https://permalinks.23andme.com/pdf/23_21-PRSMethodology_May2020.pdf.
