Searchable abstracts of presentations at key conferences in endocrinology
Endocrine Abstracts (2010) 22 S13.2

ECE2010 Symposia The TSH reference range (4 abstracts)

Health outcomes related to TSH values within the reference range

Bjørn Olav Åsvold 1,


1Norwegian University of Science and Technology, Trondheim, Norway; 2St Olavs Hospital, Trondheim University Hospital, Trondheim, Norway.


There is increasing evidence that differences in thyroid function within the clinically normal range, as defined by TSH within the reference range, is associated with health outcomes.

TSH within the reference range is positively associated with presence of thyroid antibodies and with risk of overt hypothyroidism. Some cross-sectional studies indicate that low-normal thyroid function may be associated with adverse serum lipid levels, high blood pressure, high body mass, endothelial dysfunction, and atherosclerosis, whereas high-normal thyroid function may be associated with atrial fibrillation and osteoporosis. Among prospective studies, one indicated that women with low-normal thyroid function may be at increased risk of fatal coronary heart disease. Another study showed that people with high-normal thyroid function may have increased risk of atrial fibrillation. Others found no association between TSH within the reference range and vascular mortality or coronary heart disease events. In very old age, there is evidence that high-normal thyroid function may be associated with higher mortality.

In summary, several studies indicate that low-normal thyroid function is associated with increased risk of autoimmune hypothyroidism, with adverse levels of cardiovascular risk factors, and possibly with increased risk of atherosclerosis. On the other hand, high-normal thyroid function may be associated with increased risk of atrial fibrillation and osteoporosis. However, few prospective studies have addressed health outcomes related to differences in TSH within the reference range, and the results have not been consistent. There is almost no evidence from clinical trials to suggest that treating TSH levels within the reference range may be beneficial.

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