THE THYROID AND THE EYES: A doctor explains the relationship and reveals one thing we can do right now to be healthier

AUTHOR: MAJA BARETIĆ, MD, PhD, Assistant Professor

MD, PhD, Assistant Professor, Internist, Endocrinology and Diabetology Subspecialist

Learn how increased thyroid function can affect the eyes and what we can do if we get thyroid eye disease

Redness, irritation, sensitivity to light, dry eye, pressure in the eyeball, limited eye movement, double vision, blurred vision .... All these along with other signs that indicate increased thyroid function may be symptoms of a severe disease that poses the greatest risk to — smokers. That is why quitting smoking is one thing you can do right now to improve your health and protect your eyes, those small, complex, fascinating, incredibly productive and resilient organs that are responsible for the majority of the memories and experiences in our lives.

We receive as much as 90 percent of the information from our surrounding environment through our eyes. It is estimated that our eye will register an average of 24 million photos over a lifetime and blink approximately 5.2 million times each year. The eye muscles can work day and night without rest and, along with the heart, are the fastest and most loaded muscles in the body. The World Health Organization estimates that out of the 2.2 billion people suffering from eye diseases worldwide, for at least a billion of them the disease could have been prevented. Thanks to the eyes, it is possible to detect some other diseases because they reveal symptoms of diabetes, high blood pressure or even rheumatic diseases. In addition to aging and genetic predispositions, eye health is influenced by many other factors we have control over ourselves, enabling us to prevent diseases and improve our health. This is why ophthalmologists, neurologists, endocrinologists, psychiatrists, rheumatologists, otorhinolaryngologists, plastic surgeons, general practitioners, pharmacists and engineers are brought together at X-Lab — the expert research hub by JGL — to analyse the latest research and, by applying a holistic approach, to share with us how to take care of our eye health and why that is important for our whole bodies.

What connects the increased activity of the thyroid gland and eye disease, how can we help ourselves if we suffer from thyroid eye disease (Graves' orbitopathy), and why teamwork is necessary with such a diagnosis explains one of the experts, Assistant Professor Maja Baretić, MD, endocrinologist and member of the Croatian team of the European Group on Graves' orbitopathy (EUGOGO).

1 What is the thyroid gland and why is it important for the body?

The thyroid gland is a gland located in the neck, in front of the trachea, its structure is soft, and if it’s normal in size, it won’t be noticeable. It plays an important role because it secretes thyroid hormones that regulate metabolism. Proper functioning of the thyroid gland is critical for the normal functioning of the whole body, for example for the metabolism of energy, the functioning of the heart and digestive system, temperature regulation, and the development of the central nervous system.

Thyroid disease can be manifested by a change in the structure of the thyroid gland (e.g., the thyroid is enlarged or has nodules) and / or a change in the functioning of the thyroid (the thyroid is too active or not active enough). When the structure of the thyroid gland is significantly changed, an enlargement of the gland itself can be noticed on the neck, which means that the doctor will be able to feel the changes in the thyroid gland during a clinical examination. Changes in the functioning of the thyroid are manifested by symptoms that are not associated with the neck only, but with the whole body. When the functioning of the thyroid is slowed down or is underactive (hypothyroidism), this leads to signs of a slower metabolism such as weight gain, fatigue, swelling, irregular menstrual cycle, constipation, dry skin, drowsiness.

On the other hand, when the functioning of the thyroid is sped up or overactive (hyperthyroidism), this leads to signs of accelerated metabolism. Changes in the structure of the thyroid gland and its functioning don’t necessarily manifest together: one person may have nodules in their thyroid, but no changes in the normal functioning of hormones, while another may have an underactive thyroid with an almost normal structure of the thyroid.

2 What is hyperthyroidism and what should we do if we suspect we have it?

Hyperthyroidism is a condition where there are too many thyroid hormones in the body. Symptoms of hyperthyroidism are actually signs of accelerated metabolism: patients lose weight despite having a good appetite, sweat excessively, experience insomnia and mental strain, have rapid heartbeat and high blood pressure, their skin is moist and warm, they feel tired and experience increased stool frequency. Hyperthyroidism is more common in women (but not inevitably so), who then often experience menstrual disorders. Not every patient will necessarily present all the symptoms. In some, an increase in the size of the thyroid gland in the neck and changes in the eyes are visible.

What should these patients do?

If the patient has symptoms corresponding to hyperthyroidism, a hormonal disorder should be confirmed or ruled out through laboratory tests. The first step is to contact the family doctor or general practitioner who will confirm or rule out the diagnosis on the basis of their clinical experience, the symptoms and signs of the disease and laboratory tests. Sometimes the signs of our hectic lifestyles, stress or some other diseases can “imitate” an overactive thyroid gland, but the hormonal findings turn out to be normal. This does not mean that the patient isn’t experiencing some health concerns, but that they aren’t caused by thyroid disease and it’s necessary to find their real cause.

3 Why does hyperthyroidism occur and how is it related to changes in the eyes?

The most common cause of hyperthyroidism is Graves’ disease, which is an autoimmune disorder. How can we explain autoimmunity? In a healthy body, antibodies (defence proteins) serve to defend the body against, for example, infectious diseases. Normally, antibodies are produced as a response to foreign elements in the body, such as bacteria or viruses. Autoimmunity is a mistake in the immune system when the body attacks itself and this leads to disease. In Graves’ disease, antibodies produced by the body bind to the surface of thyroid cells and lead it to become overactive. The level of these antibodies can be determined in a laboratory.

If Graves’ disease is the cause of hyperthyroidism, autoimmunity will also affect the eye: antibodies lead to the thickening of the eye muscles and the tissue around the eyeball. Therefore, in addition to the symptoms of hyperthyroidism, these patients will also present changes in the eyes.

Other causes of hyperthyroidism are nodules in the thyroid gland that produce hormones excessively, inflammation of the thyroid gland that is not autoimmune in nature, some medicinal products, and the like. With the other causes of hyperthyroidism there are no changes in the eyes, because the nature of the disease that led to the thyroid gland becoming overactive is not autoimmune.

Simply put, looking a patient with hyperthyroidism in the eyes can facilitate the diagnosis significantly.

4 What is the eye disease called thyroid orbitopathy (Graves' orbitopathy) and what are its symptoms?

Graves ‘orbitopathy is an autoimmune eye disease caused by the enlargement of the muscles and the adipose tissue of the eyes and it occurs in patients with Graves’ disease. It is estimated that 25 to 50 percent of patients have clinical changes: they are sometimes very mild and inconspicuous. However, this is not the rule and some patients have severe ocular changes that affect quality of life and / or impair vision. Patients (or even their friends or family) usually notice the changes in the eyes first, which are characterized by a “bulging” appearance in one or both eyes. There is also redness, swelling of the eyelids, eye irritation, sensitivity to light, dry eye, pressure in the eyeball, limited eye movement.

Some patients describe having so-called double vision (seeing a double image of one object), others note blurred vision and severe pain. Changes in the eyes do not necessarily occur at the same time as hyperthyroidism. Some patients first experience changes in the eyes, and develop thyroid dysfunction only later. For some patients, although this is much less often, thyroid function is normal or poor.

Who is more likely to develop Graves’ orbitopathy?

Smokers and women have a higher risk, and other risk factors include genetic predispositions, antibody levels, the degree of thyroid dysfunction, and stress. Patients with Graves’ disease and orbitopathy tend to be slightly older compared to patients with Graves’ disease who don’t have orbitopathy.

5 How is Graves' orbitopathy treated, and what can a patient do?

Graves’ orbitopathy is treated by a team of doctors: because it is a disease that affects several interconnected organ systems, a multidisciplinary approach is essential, one that includes an ophthalmologist and an endocrinologist, or a specialist in nuclear medicine. The treatment is carried out according to the international guidelines of the European Group on Graves’ orbitopathy. This is a multidisciplinary group of experts from a number of European centres (including the one from Croatia) that publish guidelines for diagnosis, clinical treatment and therapy.

The guidelines state that it is important to normalize the work of the thyroid gland as soon as possible and explain when to give which medicinal product for the eye changes, as well as in what dose. With severe forms of the disease, in addition to the use of medicinal products and treatment in the form of eye drops, subcutaneous injections, tablets and infusions, orbital radiation or surgical treatment of the eye is also considered.

What can the patient do?

It is necessary to take the prescribed medication regularly, have regular check-ups and stop smoking. Smoking is a leading risk factor, one that can easily be avoided, that affects the incidence, course and prognosis of the disease extremely negatively.

Finally, I will quote US President J. F. Kennedy: “Don’t ask what your country can do for you, but what you can do for your country.” It is the same with the eyes: if the patient has Graves’ orbitopathy, the doctor’s instructions should be followed, unverified information involving dieting, iodine preparations and the like should not be trusted, and most importantly the patient should — STOP SMOKING!


The 2021 European Group on Graves’ orbitopathy (EUGOGO) clinical practice guidelines for the medical management of Graves’ orbitopathy. Eur J Endocrinol. 2021