Washington, April 3 (IANS) Young adults with overactive thyroids face a 44 percent increased risk of stroke compared to those with normal thyroid functions, a new study says.

"Strokes of undetermined cause account for between one-third and one-fourth of all ischemic strokes in young people," Herng-Ching Lin, senior study author and professor at the School of Health Care Administration, College of Medicine in Taipei, Taiwan, said.

"To the best of our knowledge, hyperthyroidism has never been considered as a potential risk factor for stroke in the 18 to 44 age group," Lin added.

Ischemic stroke occurs when an artery to the brain is blocked. If an artery is blocked, the brain cells (neurons) cannot make enough energy and will stop working and die. This is why immediate medical treatment is absolutely critical.

Hyperthyroidism, also known as overactive thyroid, is a common endocrine disorder that affects an estimated 0.5 percent (one in 200 people) to two percent (one in 50 people) of the world's population, including a significant group of young adults, Lin said.

The condition causes overproduction of thyroid hormone, which speeds up the metabolism and causes symptoms such as sweating, weight loss, diarrhoea and nervousness, a release of College of Medicine said.

Researchers used data on 3,176 young adults diagnosed with hyperthyroidism between Jan 1, 1998 and Dec 31, 2001 and 25,408 patients free of thyroid disease. The patients' average age was 32 years.

The study appeared in Stroke: Journal of the American Heart Association.