Hyperthyroidism can cause dry eyes, and it does so through multiple pathways. The most common route is thyroid eye disease (TED), a condition that develops in roughly 40% of people with Graves’ disease, the leading cause of hyperthyroidism. TED triggers both physical changes to the eye area and immune-driven damage to the tear glands, both of which disrupt the tear film and leave the eyes feeling dry, gritty, or irritated.
How Hyperthyroidism Leads to Dry Eyes
The connection between hyperthyroidism and dry eyes isn’t simply about hormone levels being too high. It’s primarily driven by autoimmune activity. In Graves’ disease, the immune system produces antibodies that attack the thyroid. Those same antibodies also target tissues in and around the eyes, including the muscles, fat, and tear-producing glands in the orbit.
The tear glands (lacrimal glands) have receptors for thyroid-stimulating hormone on their surface, which makes them a direct target for the autoantibodies circulating in Graves’ disease. When those antibodies bind to the tear glands, they trigger inflammation and tissue damage that reduces tear production. Studies measuring tear output show this clearly: patients with thyroid eye disease produce significantly less tears, averaging about 14 mm on a standard tear test compared to roughly 25 mm in healthy controls.
At the same time, the autoimmune attack triggers a cascade of inflammatory signals in the orbital tissue. Immune cells flood into the area behind the eyes, causing swelling of the muscles and fat that surround the eyeball. This swelling pushes the eyes forward (a condition called proptosis or exophthalmos) and forces the eyelids to retract, creating a wide-eyed appearance. Both proptosis and lid retraction are extremely common, each affecting about 57% of Graves’ disease patients.
Why Tears Evaporate Faster
Even when the tear glands are still producing some tears, the physical changes around the eye make it nearly impossible for the tear film to stay intact. A wider gap between the upper and lower eyelids exposes more of the eye’s surface to air, speeding up evaporation. Bulging eyes can prevent the lids from closing completely during blinks or sleep, leaving portions of the cornea unprotected.
Incomplete blinking is another underappreciated factor. When the eyelid muscles are stiff or restricted by swollen tissue, each blink fails to spread tears evenly across the surface. The tear film breaks apart faster as a result. In thyroid eye disease patients, tear breakup time drops to about 6 seconds, compared to roughly 11 seconds in people with healthy eyes. That faster breakup means the eye surface is repeatedly left exposed between blinks, triggering the burning, stinging, and foreign-body sensation that characterizes dry eye.
The combination of reduced tear production and increased evaporation also raises the salt concentration of whatever tears remain. Tear osmolarity in thyroid eye disease patients averages around 340 mOsm, well above the normal range of about 290 mOsm. That higher salt concentration further irritates the eye surface, creating a cycle of inflammation and dryness.
Smoking Dramatically Increases the Risk
If you have Graves’ disease and smoke, your risk of developing thyroid eye disease jumps substantially. Research shows smoking increases the odds of TED by as much as 7.7 times compared to nonsmokers. Even among those who already have TED, smokers face a 2.6-fold higher incidence of proptosis and a 3.1-fold higher incidence of double vision. The more severe the eye disease, the worse the dry eye symptoms tend to be. Quitting smoking is one of the single most impactful things you can do to protect your eyes if you have an overactive thyroid.
Managing Dry Eyes With Thyroid Disease
Lubricating eye drops are the first-line approach for dry eyes related to thyroid disease, and clinical guidelines recommend them for all patients with TED regardless of severity. Preservative-free artificial tears used throughout the day help compensate for both low tear production and rapid evaporation. For nighttime, thicker gel-based lubricants or ointments can protect the cornea if your eyelids don’t fully close during sleep. Simple environmental adjustments also help: using a humidifier, avoiding direct airflow from fans or vents, and wearing wraparound glasses outdoors to reduce wind exposure.
Selenium supplementation has shown genuine benefit for mild thyroid eye disease. A clinical trial published in the New England Journal of Medicine found that taking 100 micrograms of selenium twice daily for six months significantly reduced eye involvement, improved quality of life, and slowed disease progression compared to placebo. The benefit was specific to patients with mild disease, so this isn’t a treatment for advanced cases, but it’s a low-risk option worth discussing early on.
Treatment for More Severe Cases
When thyroid eye disease is active and causing significant proptosis, a newer treatment targeting a specific growth factor receptor on orbital cells has shown striking results. In a phase 3 trial, 83% of patients receiving this treatment achieved a meaningful reduction in eye bulging (at least 2 mm) after 24 weeks, compared to just 10% on placebo. Reducing proptosis directly addresses one of the root causes of dry eye by allowing the eyelids to cover more of the eye surface again. Disease activity scores also dropped significantly, with 59% of treated patients reaching near-zero inflammation.
For the most severe cases involving corneal breakdown from exposure, surgical options include orbital decompression (reducing pressure behind the eye to let it settle back into a more normal position) and procedures to correct lid retraction. These address the mechanical causes of dryness when medical treatment alone isn’t enough.
Dry Eyes Without Obvious Eye Disease
Not everyone with hyperthyroidism will develop the classic bulging eyes or visible swelling of thyroid eye disease. Some people experience dry eye symptoms as their only ocular complaint. This can happen because the autoimmune process affects the tear glands at a subclinical level, causing subtle inflammation that reduces tear quality without producing the dramatic physical changes associated with full-blown TED. If you have Graves’ disease and your eyes feel persistently dry, irritated, or watery (paradoxically, excessive tearing can be a sign of underlying dryness), it’s worth getting a thorough eye evaluation even if your eyes look normal in the mirror.
Getting thyroid hormone levels under control is an important piece of the puzzle, since uncontrolled hyperthyroidism tends to worsen eye symptoms. However, eye disease can develop or progress even after thyroid levels normalize, because the autoimmune process in the orbit operates somewhat independently of thyroid function. This is why ongoing monitoring of eye symptoms matters even when your thyroid numbers look good on bloodwork.