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At some point, you may have been told that you have a “fatty liver.” If you’re a thyroid patient who’s heard this from your doctor, how concerned should you be? What does this term even mean?! And, for those of you who’ve been diagnosed with fatty liver, do you know about the vital link between “fatty liver” and hypothyroidism? In this article, we look at fatty liver and the connection to an underactive thyroid, as well as essential steps you can take to keep your liver healthy.
“Fatty liver” disease – also known as hepatic steatosis – refers to abnormally high levels of fat (lipids) concentrated in the liver. In the past, experts attributed fatty liver disease to the overconsumption of alcohol. Nonalcoholic fatty liver disease, or NAFLD, is a new category of chronic liver disease not tied to alcohol consumption that was only identified in 1981.
A 2020 study in the Journal of Clinical and Translational Hepatology stated that “in the last 20 years, NAFLD has become one of the most common liver diseases in the world, encompassing almost 25% of the world’s population.” In the U.S., an estimated 80 to 100 million people have NAFLD. The rapid increase in NAFLD is thought to be a result of increasing rates of obesity and metabolic syndrome across the globe.
NAFLD is an umbrella term that encompasses four stages of liver disease, including:
Stage 1. Liver steatosis, also known as simple steatosis, features higher than normal levels of fat in the liver, without liver inflammation or liver damage. According to research, about 20 to 25% of people with Stage 1 liver steatosis go on to Stage 2.
Stage 2. Nonalcoholic steatohepatitis, known as NASH, is a more acute form of liver steatosis involving more extensive fatty infiltration of the liver, liver inflammation (hepatitis) and some degree of liver damage. Research shows that, within 10 to 20 years, between 4 and 20% of people with NASH will go on to Stages 3 and 4.
Stage 3. Liver Fibrosis, with inflammation, liver scarring, and excess fibrous tissue in the liver.
Stage 4. Cirrhosis, including permanent damage to the liver, and more extensive scar tissue in the liver, with a potential for liver failure and the need for a liver transplant. (Note that the cirrhosis and liver failure seen in NAFLD are similar to that seen in chronic alcoholics.)
Experts estimate that annually, around 2.6% of Stage 4 NAFLD patients with cirrhosis will then go on to develop a form of liver cancer known as hepatocellular carcinoma or HCC.
Research shows that the two most important risk factors for NAFLD are insulin resistance and obesity. NAFLD is more likely to develop at the same time as, or after, a diagnosis of obesity or higher body mass index (BMI), insulin resistance and impaired glucose metabolism, a diagnosis of prediabetes or type 2 diabetes, and elevated blood pressure. These markers fall under the umbrella term called “metabolic syndrome.”
Other risk factors include:
- Overconsumption of carbohydrates
- A sedentary lifestyle
Research also shows that NAFLD can also be triggered by viruses, certain drugs, and various endocrine diseases, including polycystic ovary syndrome (PCOs) and hypothyroidism.
Stage 1 NAFLD is usually asymptomatic, or symptoms may include mild fatigue or discomfort in the upper right side of the abdomen.
When NAFLD progresses to Stage 2, the symptoms of NASH can include significant fatigue, muscle weakness, weight loss, yellowing skin or eyes, and localized or widespread itching.
At Stage 4, the symptoms of cirrhosis can include bloating and fluid retention, internal bleeding, and muscle wasting.
The definitive diagnostic procedure for NAFLD is a liver biopsy, but some doctors consider this test too invasive, and they make a diagnosis primarily based on imaging tests.
Specifically, the imaging techniques used in diagnosis include proton magnetic resonance spectroscopy (1H-MRS), ultrasound, computed tomography (CT scans), and magnetic resonance imaging (MRI). 1H-MRS testing is considered the most accurate and noninvasive method for measuring fat in the liver.
Be aware that there are two significant challenges in NAFLD diagnosis, however.
First, the most commonly used imaging test for NAFLD diagnosis is ultrasound, even though it’s not particularly sensitive at identifying NAFLD until it reaches more advanced stages. Specifically, fat content in your liver needs to exceed 33% to be detected by ultrasound.
Second, some doctors also believe they can diagnose NAFLD using blood tests for liver enzymes: alanine aminotransferase (ALT) and aspartate aminotransferase (AST). These general tests are often part of regular bloodwork, and abnormal levels can signal the need for a more in-depth follow-up of liver function. But they aren’t helpful for diagnosing NAFLD because only around 30% of people with NAFLD have abnormal levels of ALT and AST.
In general, however, experts recommend that if you have any abnormal results on blood tests for liver function and have even one metabolic risk factor, you should undergo comprehensive evaluation for possible NAFLD.
Research shows increasing evidence of an association between hypothyroidism and NAFLD, and have identified an underactive thyroid a standalone cause of NAFLD in some people. The evidence is so compelling that experts have created a new disease category of NAFLD called hypothyroidism-induced NAFLD, or HIN.
Both overt hypothyroidism and subclinical hypothyroidism are considered independent risk factors for NAFLD.
Specifically, hypothyroidism – both the overt and subclinical forms – is far more common in NAFLD patients compared to the general population. Approximately 17% of people with NAFLD have hypothyroidism. Interestingly, according to research, the higher the thyroid stimulating hormone (TSH) level, the greater the risk of NAFLD.
The linkage goes both ways. Multiple studies have shown that patients with hypothyroidism have a 2.7-fold higher risk of developing NAFLD and NASH!
While experts are still exploring the complexities of the relationship between an underactive thyroid and NAFLD, there are some theories about this connection.
- Thyroid hormones are essential for liver function and liver metabolism. Insufficient levels of thyroid hormones promote fatty infiltation of the liver, impairing its ability to metabolize fat, and increasing the risk of NAFLD.
- Hypothyroidism increases the risk of developing insulin resistance and impaired glucose metabolism, another risk factor for NAFLD.
- Up to 90% of hypothyroid patients have abnormal lipid values.
- Hypothyroidism increases the risk of impaired fat processing. Up to 90% of hypothyroid patients have abnormal serum lipids , including high cholesterol and triglyceride levels. These are all risk factors for NAFLD.
- Hypothyroidism increases the risk of being overweight or obese, which are risk factors for NAFLD. On average, hypothyroid patients weigh 15 to 30% more than when thyroid function is entirely normal.
The link is crucial because research has found that early diagnosis and treatment of hypothyroidism – along with changes to diet and other lifestyle practices – may help prevent the development and progression of NAFLD. There is also clear evidence that treatment of hypothyroidism can significantly improve some liver conditions, including hypothyroidism-induced NAFLD.
There is no definitive treatment for NAFLD. Instead, the recommended treatment for NAFLD involves a combination of approaches, including:
- Losing weight
- Taking medication that reduces lipids (cholesterol and/or triglycerides)
- Taking medication to treat insulin resistance, reduce blood sugar, and achieve better control of diabetes and prediabetes
- Reducing alcohol consumption
- Reducing the intake of carbohydrates and high-fructose foods
- Increasing the level of physical activity
- Making other dietary changes
Experts are increasingly exploring the potentially crucial role of thyroid hormone replacement drugs for patients with NAFLD and even subclinical or borderline hypothyroidism. One study of patients with NAFLD and subclinical hypothyroidism found that 15 months of treatment with levothyroxine reduced the prevalence of NAFLD by almost half!
There’s even evidence that low-dose thyroid hormone replacement may be helpful for NAFLD patients with normal thyroid function! One study of patients with type 2 diabetes and NAFLD – and normal thyroid levels– put those patients on a 16-week trial of low-dose thyroid hormone medication. This four-month treatment program resulted in significant reductions in liver fat!
There’s also promising news on the horizon: A new thyroid hormone receptor (THR) β-selective agonist drug called Resmetirom is currently in clinical trials. The drug has shown promise as a treatment for NASH and preventing progression from NASH to cirrhosis.
One in six patients with NAFLD has borderline or subclinical hypothyroidism, leading experts to conclude: “Early identification of at-risk patients is important since treatment of the hypothyroidism may reduce the risk of NAFLD and potential complications.”
Unfortunately, many physicians overlook the association between thyroid dysfunction and NAFLD, missing miss the opportunity to address a treatable underlying cause of the problem. So, if you have NAFLD, you should advocate for yourself by familiarizing yourself with the symptoms of hypothyroidism, and getting regular thyroid screening and evaluation.
If you have been diagnosed with NAFLD but don’t know if you have underlying hypothyroidism, the Paloma Complete Thyroid Blood Test kit makes it simple and affordable to test for an underactive thyroid right from home. The Paloma home thyroid test kit comes with everything needed for sample collection for thyroid hormone levels, including thyroid stimulating hormone (TSH), free T3, free T4, and Thyroid Peroxidase (TPO) antibody levels. Your thyroid test kit, which is mailed to your address, requires only a painless finger prick. You then use the prepaid mailer to send the kit back to our lab, and within days, your thyroid lab results are released to your secure online dashboard.
Many experts recommend patients with NAFLD who have evidence of even mild hypothyroidism start thyroid medication, because treatment can reduce the risk and progression of NAFLD in those patients.
If you are hypothyroid, aim for optimal thyroid treatment as a starting point in the prevention of NAFLD. You can also work with your healthcare provider to address insulin resistance and weight gain, other risk factors for NAFLD. If you have any abnormal liver function results on blood tests, and one or more markers for metabolic syndrome, you should be evaluated for the possibility of NAFLD because early intervention can prevent the progression of NAFLD.
For careful diagnosis, management, and optimal treatment of hypothyroidism, many thyroid patients choose virtual visits with Paloma’s top thyroid doctors. Paloma’s thyroid-savvy team of doctors work with you to develop a thorough and effective treatment program, including the best thyroid medication that can safely normalize your thyroid function and best resolve your symptoms.
Because nutritional changes are also a key component of treatment for NAFLD, you may want to schedule a consult with one of Paloma’s registered nutritionists. As experts in healthy eating for people with hypothyroidism, our experienced nutritionists can help you make nutritional choices to support the health of your thyroid and liver.