As COVID-19 enquiries pour in from concerned thyroid patients, we thought it would be helpful to take a look at some of your questions.   Dr Petros Perros, BTF Patron and Consultant Endocrinologist at the Royal Victoria Infirmary, Newcastle upon Tyne kindly addresses one patient’s question about infection risk and keeping our immune system healthy at this time:

Our member asks:

I have an underactive thyroid (hypothyroidism). Am I more prone to infections? How can I keep my immune system as healthy as possible?

Dr Perros writes:

Thank you for contacting us. There is understandably a lot of concern about whether people living with thyroid disease are more prone to infections, including COVID-19. You will hopefully be reassured by the information posted on the BTF website which has been prepared with The British Thyroid Association and Society for Endocrinology.

The main messages are:

  • Levothyroxine used to treat an underactive thyroid (hypothyroidism) and antithyroid drugs (carbimazole and propylthiouracil) used to treat an overactive thyroid (hyperthyroidism) do not suppress your immune system.

  • ‘Thyroid disease is not known to be associated with increased risk of viral infections in general, nor is there an association between thyroid disease and severity of viral infection’. This information is based on the collective experience of many thyroid experts who have treated many thousands of patients with thyroid disease. There is also some indirect evidence from studies, such as that for Journy et al, (2017) who looked at causes of death of women with hyperthyroidism or hypothyroidism from cancer, heart disease, diabetes and all other causes, and found that there was no excess deaths from other causes which will have included infections. There is some evidence that patients who have uncontrolled hypothyroidism (i.e. very high serum TSH) have impaired immune function. This returns to normal once corrected with thyroid hormones. (Schoenfeld et al, 1995).

To answer your question about keeping our immune systems healthy as possible. There are a number of things you can do:

Take your medication regularly

If you are on thyroid medication please make sure that you take it regularly. It is astonishing how often we do not. Approximately 50% of us don’t take prescribed medication regularly, any type of medication (Brown et al, 2016). In the USA between half to 2/3 of patients on levothyroxine fail to take it regularly (Ladenson, 2002, Hepp et al, 2018). Even in pregnancy, when motivation is greater than other times, and the consequences of poorly controlled hypothyroidism for the baby can be devastating, about 17% of women don’t take their thyroid medication regularly (Juch et al, 2016). Now it is more important than ever that we get into the habit of taking our prescribed meds regularly.

If you are on immunosuppressive medications like chemotherapy this will put you in a high risk category and your doctor should have been in contact with you to discuss both your medication and taking self-isolation measures. Please follow the advice of the doctor/specialist who has prescribed your medication. He or she will be in the best position to judge where the balance lies in your particular case, between risking deterioration in the condition for which you are on that particular medication, and the risk of infection.

To supplement or not to supplement?

Our ability to fight infections depends on numerous factors which include genetic, age (extremes of age are more susceptible), other conditions and diseases (like cancer, diabetes), medications (like chemotherapy, steroids), nutrition (obese and underweight are more prone) and lifestyle (smoking, excess alcohol, physical inactivity). A lot of attention has been placed on nutritional factors and several food items have been highlighted as being beneficial. The list includes vitamin D, vitamin E, zinc, fish oil and polyunsaturated fatty acids, probiotics and green tea. This topic has been reviewed by Wu et al (2019), but the evidence is mixed and contradictory. Furthermore, for some of the nutrients it is possible that over-supplementation may impair the immune system. The conclusion is that there is no evidence for or against using such supplements, except in people with proven deficiency.

If you have been vitamin D deficient in the past, it is likely that you will be again especially in the winter, so it seems reasonable to increase your vitamin D intake.(The current UK guidance for adults is to consider taking 10 mcg daily over the winter months) You can do that by increasing the amount of oily fish in your diet, increasing your exposure to sun or by taking vitamin D supplements. For all the other nutrients mentioned above the evidence for and against is conflicting and there is the chance that if you overdo it you may do harm.

Maintaining a balance

My opinion is there is a good case here for having a varied and healthy diet with plenty of fruit, veg, pulses, fish and moderate amounts of meat. That will ensure that you will not become deficient. At the same time, you will not be exposed to the risks of over-supplementing. 

Shedding the excess weight that many of us carry will also be helpful. During social isolation most of us have more time to ourselves and it is a good opportunity to pay more attention to improving our lifestyle, so giving up/reducing smoking and avoiding overindulging in alcohol will all be beneficial to our health.

Further information

NHS information on Vitamin D

BTF article on vitamin D and thyroid disease

You can also find the answers to some frequently asked questions in our Thyroid Disease and COVID-19' statement prepared with assistance from the British Thyroid Association and Society for Endocrinology

Articles on the management of thyroid disease, including topics such as thyroid disease and hair loss and thyroid disease and osteoporosis

More information on living with thyroid disorders is available here. Many patients also find our network of volunteer telephone contacts and local support groups a valuable resource.

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Please note: This guidance is not intended as a substitute for taking advice from your own doctor or specialist as they will be best placed to advise you


Brown MT, Bussell J, Dutta S, Davis K, Strong S, Mathew S. Medication Adherence: Truth and Consequences. Am J Med Sci. 2016 Apr;351(4):387-99.

Hepp Z, Lage MJ, Espaillat R, Gossain VV. The association between adherence to levothyroxine and economic and clinical outcomes in patients with hypothyroidism in the US J Med Econ. 2018 Sep;21(9):912-919.

Journy NMY, Bernier MO, Doody MM, Alexander BH, Linet MS, Kitahara CM. Hyperthyroidism, Hypothyroidism, and Cause-Specific Mortality in a Large Cohort of Women. Thyroid. 2017;27(8):1001–1010.

Juch H, Lupattelli A, Ystrom E, Verheyen S, Nordeng H. Medication adherence among pregnant women with hypothyroidism-missed opportunities to improve reproductive health? A cross-sectional, web-based study. Patient Educ Couns. 2016 Oct;99(10):1699-707.

Ladenson PW. Psychological wellbeing in patients. Clin Endocrinol (Oxf). 2002 Nov;57(5):575-6.

Schoenfeld PS, Myers JW, Myers L, LaRocque JC. Suppression of cell-mediated immunity in hypothyroidism. South Med J. 1995;88(3):347–349. 

Wu D, Lewis ED, Pae M, Meydani SN. Nutritional Modulation of Immune Function: Analysis of Evidence, Mechanisms, and Clinical Relevance. Front Immunol. 2019;9:3160.


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