TSH is often the first test doctors use to determine whether you have too little or too much thyroid hormones. High TSH is often linked to an underactive thyroid or hypothyroidism. Read on to learn about the causes, symptoms, and health effects of high TSH levels.
Causes of High TSH
Causes listed below are commonly associated with higher TSH. However, while an abnormal TSH test can indicate there is a problem, it can’t pinpoint the cause. In addition, a result that’s higher than normal doesn’t necessarily mean that you have a health condition needing treatment.
Your doctor will usually follow this result with additional testing to investigate why your TSH is high. Work with your doctor or another health care professional to get an accurate diagnosis.
1) Hypothyroidism (Underactive Thyroid)
TSH often increases in response to an underactive thyroid gland (primary hypothyroidism) .
A relatively common cause of hypothyroidism is Hashimoto’s thyroiditis, an autoimmune disorder in which the immune system attacks and gradually destroys the thyroid gland .
2) Iodine Deficiency or Excess
Both iodine deficiency or excessive iodine intake can result in an elevated TSH [2, 3].
Globally, the most common cause of hypothyroidism is iodine deficiency .
Thyroid hormones are made from the chemical iodine, which humans need to get from the food they eat. Not getting enough iodine in the diet (severe iodine deficiency) can lead to hypothyroidism, and may even cause goiters (a large swelling of the thyroid gland that bulges out from the neck) [4, 5].
Many studies also show that excessive iodine intake can also lead to hypothyroidism (>150 μg for people with existing thyroid diseases, or >1,100 μg for health individuals) .
For example, children living in an area with abnormally high iodine concentrations in their drinking water show higher rates of thyroid dysfunction (increased levels of TSH and thyroid antibodies) .
Animal and cell studies show that excess iodine can be toxic to the thyroid gland and lead to thyroid cell death [7, 8, 9].
Overeating is another common cause of thyroid dysfunction. A study found that chronic overeating led to an increase in T3 levels over both the short- and long-term (from 3 weeks up to 7 months) .
Directly tied to overeating, being severely overweight can also raise TSH levels [11, 12].
Two separate studies have shown that among women, overweight and obese ones have higher TSH levels than normal-weight patients. This includes people with higher overall body weight and body mass index (BMI), larger waist size, and higher body fat percentage [13, 12].
Another study found that healthy young women with high TSH levels were found to be twice as likely to have metabolic syndrome (a condition that causes obesity, high blood pressure, and high levels of sugar, fat, and cholesterol in the blood) when compared to women with lower TSH levels .
The link between TSH and obesity doesn’t apply only to women, either: two large-scale studies have shown that higher TSH levels are associated with a higher BMI in both male and female patients alike [15, 16].
TSH is involved in the weight of children as well. Obese and overweight children have higher TSH levels, and these high levels are linked to increases in cholesterol, fat, and blood pressure .
4) Radiation Therapy
Radiation therapy in the head and neck area can damage the thyroid gland and thereby cause hypothyroidism. This, in turn, increases TSH levels .
5) Pituitary Tumors
Although rare, tumors of the pituitary gland can sometimes produce and release excessive amounts of TSH [19, 20].
6) Some Toxins, Drugs, and Supplements
Some toxins, drugs, and supplements can increase TSH, including:
- Lithium therapy [21, 22, 23, 24, 25].
- Opioids, including morphine, methadone, and buprenorphine [26, 27, 28, 29, 30].
- Metyrapone (Metopirone), used to treat Cushing’s syndrome .
- Arsenic .
- Perchlorates found in rocket fuels .
- Dopamine inhibitors (metoclopramide, domperidone, sulpiride, monoiodotyrosine) [34, 35].
7) Rare Genetic Disorders
Certain rare genetic disorders can result in elevated TSH levels .
TSH levels normally increase as we age .
High TSH is commonly caused by hypothyroidism (low thyroid hormone levels), in which case a person may experience:
- Fatigue 
- Constipation 
- Weight gain 
- Depression 
- Anxiety 
- Memory problems [40, 41, 42]
- Attention issues 
- Dry skin 
- Sensitivity to the cold 
However, high TSH can also be caused by conditions other than hypothyroidism, in which case symptoms will vary depending on the underlying condition.
Health Effects of High TSH
1) Heart Disease
A study with over 30k people revealed that people with higher TSH levels tended to also have higher blood pressure .
TSH has also been linked to high blood pressure in children, especially in overweight children .
A meta-analysis of data from over 55k patients found that people with very high TSH levels had a higher chance of developing (and dying from) heart disease .
Two studies have reported that higher TSH levels were linked to higher levels of fat (triglycerides) and “bad” cholesterol (low-density lipoproteins, or “LDL”) [47, 48].
Another study with almost 21k people showed similar results, and also found that higher TSH levels are correlated with lower levels of “good” cholesterol (high-density lipoproteins, or “HDL”) .
Both high bad cholesterol and low good cholesterol are known risk factors for heart disease.
2) Thyroid Cancer
Various studies including a meta-analysis have found that having a high TSH level may be a risk factor for developing thyroid cancer [50, 51, 52, 53].
A study showed that higher TSH levels were correlated with faster cancer progression in 126 patients with a specific type of thyroid cancer (papillary thyroid microcarcinoma) .
3) Healthy Aging
High TSH levels may have different effects depending on one’s age.
TSH levels naturally increase as we get older [55, 56, 57, 58, 59]. Studies suggest that when that doesn’t happen, lower TSH levels may contribute to declining mental health among the elderly.
There are several studies that suggest slightly elevated TSH may be beneficial in seniors when it comes to:
- Cognitive function [55, 60, 61, 62]
- Bone health [63, 64, 65]
- Physical health and shape 
- Longevity [67, 68]
A high TSH test can indicate there is a problem, but can’t pinpoint the cause. That’s because a high TSH can be a result of many different health conditions that all need different approaches and treatments.
It’s important to work with your doctor to find out what’s causing your high TSH levels and then to treat any underlying conditions.
Trying to artificially decrease your TSH with lifestyle modifications or supplements likely won’t address the underlying condition and may instead make it worse.
If you have an underactive thyroid (hypothyroidism), treatment will depend on your hormone levels, medical history, and your signs and symptoms. While subclinical hypothyroidism with mildly increased TSH levels is usually not treated, the standard treatment for other forms of hypothyroidism involves a daily dose of synthetic thyroid hormone medication that can restore thyroid hormone levels and reverse the signs and symptoms of hypothyroidism. But keep in mind that it may take some time to adjust the dosage of thyroid hormones so they are right for you .
If your TSH levels are mildly elevated, make sure you get enough sleep before testing next time. Studies suggest that a lack of sleep may slightly increase TSH levels (in the short term) [69, 70].
If you have digestive issues, stay away from offending foods. A study suggests that avoiding dairy products may help decrease TSH levels in people who are lactose intolerant . Similarly, maintaining a strict gluten-free diet may help decrease TSH in people with celiac disease .
This post is part of a three-part series about TSH. Check out:
- How the TSH blood test works and what the normal TSH range is
- The causes, symptoms, and health effects of low TSH