Fish Oil and Thyroid Relationship

Fish Oil and Thyroid Relationship

Approximately 300 million people around the world suffer from thyroid disorders.


Genetics, as well as environmental exposure, are common risk factors for the disease.


The most prevalent thyroid conditions are hypothyroidism and hyperthyroidism, and, according to a study by Bajaj et al, leaving them untreated can lead to the development of many maladies, particularly cardiovascular disorders.


With that being said, fish oil’s benefits on heart health has been touted as the new savior for people at risk of developing cardiovascular disease due to thyroid dysfunction.


Thyroid Disorders and Cardiovascular Health

Thyroid hormones affect many of the body’s metabolic activities.


As such, aberrations in thyroid homeostasis can affect lipid levels in the body. Additionally, it can further lead to the development of several cardiovascular problems.


Even if a person has normal TSH levels, the existence of thyroid dysfunction can lead to increases in the following:


  • Total Cholesterol, the total measure of cholesterol in the bloodstream. The desirable level for total cholesterol is anywhere below 200 mg/dl.
  • Low-Density Lipoprotein Cholesterol or ‘bad cholesterol,’ which leads to buildup and obstruction in the vessels. The optimal level for this is less than 100 mg/dl.
  • Triglycerides, fat in the blood which can further increase the risk of developing heart disease

Similarly, Rizos and his colleagues have postulated that increases in TSH levels were in tune with decreases in High-Density Lipoprotein Cholesterol. Also known as ‘good cholesterol,’ it can actually get rid of cholesterol buildup in the arteries.


A rate of 60 mg/dl and higher is deemed protective against heart conditions.


Apart from affecting cholesterol levels, thyroid disorders also affect metabolic functions which further increase one’s risk of developing cardiovascular disease.



Hypothyroidism, otherwise known as an underactive thyroid gland, is a disorder characterized by the body’s inability to produce the needed amount of thyroid hormone.


This can be caused by autoimmune disease, surgical removal of the thyroid gland, radiation therapy, thyroiditis, congenital hypothyroidism, pituitary gland damage, low intake of iodine, and intake of certain medications.


Common in women, hypothyroidism symptoms are often barely noticeable. They include:


  • Fatigue
  • Depression
  • Sensitivity to cold
  • Slow heart rate
  • Puffy face
  • Weight gain
  • Muscle weakness, aches, or tenderness
  • Joint pain, stiffness, or swelling
  • Hoarse voice
  • Dry skin and thin hair
  • Elevated blood cholesterol levels
  • Irregular menstruation

If left undiagnosed and untreated, hypothyroidism, which is prevalent in 4.6% of the general population, can lead to the development of many conditions, such as heart disease, obesity, joint pain, and infertility.


Overt Hyperthyroidism

Of the common thyroid disorders, overt hypothyroidism is the one that exerts the most adverse effect on a person’s cholesterol levels.


It is, in fact, a symptom of the disease. As such, hypothyroid patients have been known to exhibit high levels of total cholesterol, low-density lipoprotein cholesterol, and triglycerides.


Surges in the first three have been linked with an increased risk of developing CVD.


Although this is the case, in some cases, some have been known to exhibit elevated levels of high-density lipoprotein cholesterol.


Apart from cholesterol level increases, hypothyroidism upsets other bodily functions that can further promote the risk of developing coronary artery disease. Such mechanisms include:


  • Arterial hypertension
  • Vascular stiffness
  • Impairment in endothelial function
  • Increase in the thickness of the carotid intima media
  • Increase in plasma homocysteine levels which lead to kidney function deterioration
  • Increase in uric acid and phosphate levels
  • Resistance to insulin

Proving this claim is a study made by Auer et al. The research dealt with 100 patients who underwent coronary angiography and had their thyroid functions assessed afterwards.


Results showed that those who have high coronary artery disease risk (2 or 3 narrowed heart vessels) have low levels of T3, a hallmark finding of hypothyroidism.


If diagnosed immediately, lipid derangement in hypothyroid patients can normalize after 4-6 weeks of Thyroxine therapy.


While some experience falls in cholesterol levels, some develop secondary dyslipidemia. However, these individuals cannot start therapy immediately as the physician needs to evaluate the patient’s thyroid function prior to treatment.


After all, statin therapy and hypothyroidism BOTH bring about an increase in creatine kinase. Such can lead to an erroneous diagnosis of heart attack and other neuromuscular conditions.


Subclinical Hypothyroidism

It is not only the overt hypothyroid who suffer from an increased risk of suffering from heart disorders. Those with subclinical hypothyroidism can experience this as well, at least according to a study done by Rizos et al.


Subclinical hypothyroidism, which is characterized by increased TSH and normal T3 and T4, has been known to increase one’s risk of developing myocardial infarction (heart attack) and aortic atherosclerosis (plaque deposition in the heart artery.)


This happens because of subclinical hypothyroidism’s ability to increase total cholesterol and low-density lipoprotein cholesterol.


In some cases, increased triglyceride and high-density lipoprotein cholesterol have been noted as well.


As with the prior illness, cholesterol levels have been known to decrease following the thyroxine therapy of patients with subclinical hypothyroidism.



Hyperthyroidism, or an overactive thyroid, is a condition wherein there is excess production of the hormone thyroxine.


It is often caused by Graves Disease or thyroiditis, with the former running in families and putting afflicted kins in relative risk.


Immune deficiencies and viruses, as well as excessive intake of thyroid medications, can also lead to the onset of hyperthyroidism.


Hyperthyroidism works by accelerating metabolism, and its symptoms (as stated below) are usually mistaken for other conditions:

  • Immediate weight loss
  • Increased heart rate
  • Increased sensitivity to heat
  • Heightened appetite
  • Irritability, anxiety, and nervousness
  • Increased sweating
  • Tremors
  • Frequent bowel movements
  • Brittle hair
  • Thin skin
  • Sleep difficulties
  • Menstrual changes

Since hyperthyroidism affects metabolism, high thyroxine levels lead to an accelerated synthesis of adiponectin, a hormone produced by adipose tissue or body fat.


Compared to other fat-produced hormones, adiponectin has protective properties, as it reduces the risk of developing diabetes, atherosclerosis, and inflammation.


With that being said, hyperthyroidism’s effect on adiponectin is actually beneficial in reducing the risk of cardiovascular disease and atherosclerosis in afflicted individuals.


Expectedly, a study by Nigro et al has also noted that a higher adiponectin level is also linked with a lower risk of developing hypertension.


Other studies show that hyperlipidemic patients experience an unexpected decrease in cholesterol levels after developing hyperthyroidism.


Although this is the case, treatment of hyperthyroidism almost always results in the recurrence of high cholesterol levels in the aforementioned individuals.


To summarize, even with hyperthyroidism’s ability to decrease triglyceride levels, they are expected to increase once treatment has been instituted.


Fish Oil: a Way to Reduce Cardiovascular Disease Risk Brought Upon By Thyroid Disorders

As it has been mentioned, thyroid disorders, especially hypothyroidism, can increase one’s risk of developing cardiovascular conditions.


Although treatment can help lower cholesterol levels (as seen in hypothyroid patients,) it is not given as promptly as warranted as hypothyroidism symptoms are almost always barely noticeable in the beginning.


And when diagnosis is done definitively, it is usually too late to bring down the cholesterol levels to the safe parameters. This is the reason why secondary dyslipidemia often occurs in patients with thyroid disorders.


Although this is the case, a natural supplement – fish oil – has been deemed as the savior of those who suffer from thyroid-induced cholesterol problems.


After all, scientific literature shows that it is effective in combating coronary artery disease and hypertriglyceridemia – just some of the adverse health effects associated with thyroid problems.


What is Fish Oil?

Fish oil is a dietary supplement that contains Omega-3 fatty acids, which are polyunsaturated fatty acids found in fatty fish (hence the name.)


These fatty acids play various roles in many bodily functions, such as digestion, blood clotting, muscle activity, cell growth, and fertility.


The three major Omega 3-fatty acids are the following:


  • Alpha-linolenic acid (ALA), an essential fatty acid that the body cannot manufacture. Hence, this should be obtained from food such as vegetable, soybean, and canola oils.
  • Eicosapentanoic acid (EPA), a fatty acid that prevents blood from clotting right away. It is also known to decrease pain and inflammation.
  • Docosahexanoic acid (DHA), a fatty acid that plays a pivotal role in brain development and function.

Fish oil’s thrust to health fame is not new, as its effects were first observed in curiosity in 1944. The subjects - Greenland Eskimos – were observed to have a lower prevalence of coronary heart disease, optimum lipid levels, and healthy blood pressure ranges compared to Westerners.


Upon further investigation, scientists were able to link this to the high levels of omega-3 fatty acids in their bloodstreams.


This was then traced back to their diet, which consists of an average of 500 grams of fish per day. 


Fast forward to the present, and now fish oil is being utilized in the management of cardiovascular conditions.


Rich in EPA and DHA, it is effective in lowering one’s risk of developing disorders such as coronary artery disease, abnormal heart rhythms (arrhythmia,) hypertriglyceridemia, even diabetes. In fact, intake of 3-5 grams of fish oil per day can reduce triglyceride levels by as much as 50%.


After from exerting health wonders on the heart, fish oil is also known to help improve immunity and reduce inflammation.


Recommendations and Precautions

According to the US Food and Drug Administration (FDA,) the recommended dosage is 500 milligrams for regular individuals and 800-1000 milligrams for people with coronary heart disease. As much as 3 grams is recommended for individuals with high triglyceride levels (more than 200 mg/dl,) according to a study done by Weitz et al.  


Apart from supplementation, obtaining the ideal amounts of Omega-3 fatty acids can be achieved by eating oily fish at least twice a week.


Although fish oil consumption is ideal for individuals with lipid problems brought about by thyroid dysfunction, caution should be observed when it comes to eating a high-fish diet.


Variants such as mackerel, swordfish, tilefish, and shark are known to exhibit high levels of mercury. Safer alternatives include herring, salmon, sardines, trout, shrimp, and oyster.


Side Effects

Fish oil, without a doubt, is a life saver for those who are at risk of developing cardiovascular diseases. While it is all natural, it is not without side effects.


According to the US FDA, intake of Omega-3 fatty acids, whether through fish or supplementation, should not exceed the daily maximum of 3 grams.


Common side effects associated with Omega-3 fatty acids include:

  • Nausea
  • Stomach upset
  • “Fishy” burp

Most importantly, this supplement can thin the blood, so you can expect some easy bruising while taking fish oil. As such, you need to seek the doctor for advice before taking it.


This is especially the case if you are taking other blood-thinning medications such as Coumadin.


While Omega-3 fatty acids can help reduce the risk of developing cardiovascular diseases, it is known to increase low-density lipoprotein cholesterol levels by as much as 5%.


However, a study done by Artham et al shows that this is offset by fish oil’s ability to lower triglyceride levels by as much as 50%.



Artham, S. M., Lavie, C. J., Milani, R. V., Anand, R. G., O’Keefe, J. H., & Ventura, H. O. (2008). Fish Oil in Primary and Secondary Cardiovascular Prevention. The Ochsner Journal8(2), 49–60.


Auer, J., Berent, R., Weber, T., Lassing, E., & Eber, B. (2003). Https:// Journal of Clinical Cardiology, 26(12), 569-573. Retrieved November 22, 2017, from


Bajaj, J. K., Salwan, P., & Salwan, S. (2016). Various Possible Toxicants Involved in Thyroid Dysfunction: A Review. Journal of Clinical and Diagnostic Research : JCDR10(1), FE01–FE03.


Cholesterol Levels: What You Need to Know. (n.d.). Retrieved November 22, 2017, from


Hyperthyroidism: Various treatments available for overactive thyroid. (2015, October 28). Retrieved November 21, 2017, from


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Hypothyroidism (underactive thyroid). (2017, August 04). Retrieved November 21, 2017, from


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Nigro, E., Scudiero, O., Monaco, M. L., Palmieri, A., Mazzarella, G., Costagliola, C., … Daniele, A. (2014). New Insight into Adiponectin Role in Obesity and Obesity-Related Diseases. BioMed Research International2014, 658913.


Omega-3 Supplements: In Depth. (2016, July 12). Retrieved November 21, 2017, from


Rizos, C. ., Elisaf, M. ., & Liberopoulos, E. . (2011). Effects of Thyroid Dysfunction on Lipid Profile. The Open Cardiovascular Medicine Journal5, 76–84.


Weitz, D., Weintraub, H., Fisher, E., & Schwartzbard, A. Z. (2010). Fish Oil for the Treatment of Cardiovascular Disease. Cardiology in Review18(5), 258–263.


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