The risk of developing the eye disease glaucoma could be increased by having a thyroid disorder, new research has suggested.
A study by an American university found that people with glaucoma were 38% more likely to have had a thyroid disorder at some point in their life than those who did not have it.
The report, published in the British Journal of Ophthalmology, is based on a sample of more than 12,000 adults in the US, who took part in the 2002 National Health Interview Survey.
The proportion of those with glaucoma who said they had had a thyroid problem was 6.5%, compared to 4.4% who had not.
The association between glaucoma and thyroid problems was still significant even after risk factors, including gender, race and smoking habits, were accounted for.
The thyroid produces hormones which help regulate growth and the rate of chemical reactions. Glaucoma involves progressive damage to the optic nerve, which can lead to blindness.
Dr Gerald McGwin at the University of Birmingham, Alabama, said an underactive thyroid can promote chemical deposits in the mesh of vessels serving the eye, which could see pressure within the eyeball increase, a common feature of glaucoma.