High level of thyroid problems in Donegal

A high incidence of thyroid problems has been discovered in women aged over 50 living in west Donegal. The condition is strongly associated with coronary heart disease.

The two Irish researchers who discovered the high numbers of women with hypothyroidism, low thyroid function, have now launched a three-year cross-Border research programme to establish whether the problem is more widespread.

Dr Declan Bonar, a GP in Dungloe, Co Donegal, and Dr Peter Smyth, director of the endocrine laboratory at UCD, believe levels of thyroid disease could be seriously under-diagnosed in the northwest and elsewhere in the State.

The research took place over four years and is published in the current issue of the medical journal, Thyroid. It showed that women over 50 living in the region had double the rate of hypothyroidism found elsewhere in Ireland. The study also indicated a very low incidence of the disorder, 0.9 per cent, in women between 18 and 50 years of age.

The findings are particularly important in the context of the recently published cardiovascular strategy and the objective of reducing heart disease. If the screening of thyroid function leads to the earlier detection of hypothyroidism, then older women will benefit not only by the treatment of their thyroid disease but also in the prevention of coronary heart disease.

Low thyroid hormone levels are associated with high cholesterol levels and the blockage of coronary arteries. Post-menopausal women have the same high levels of heart disease as men, and so the findings could be hugely important in preventing cardiovascular problems in this age group.

The research is an example of how important findings can be generated from the relative isolation of general practice. Dr Bonar, whose practice in west Donegal was one of the first in the Republic to be computerised, noted a high proportion of women patients with reduced thyroid function. "I began to do searches for chronic disease using the computerised practice database five years ago," he said. "The levels of hypothyroidism seemed unusually high and so I got in touch with the endocrine lab in UCD to investigate the findings further."

Dr Smyth travelled to Donegal, where he undertook further investigations which involved screening for genetic markers as well as iodine levels. Low iodine is associated with reduced thyroid function, but was ruled out as a factor by further testing.

High levels of thyroid antibodies were discovered, leading to speculation that an inherited immune system problem might be to blame. While no specific link was found to known gene markers, the authors still believe this is the most likely explanation.