Subclinical Hypothyroidism

Fen-Yu Tseng

《Formosan Journal of Endocrinology and Metabolism》 5卷2期 (2014/12) Pp. 41-48

https://doi.org/10.6856/FJEM.201412_5(2).0001

摘要

Background. Subclinical hypothyroidism is defined as an elevated thyroid-stimulating hormone (TSH) level with a normal thyroxine or free thyroxine level. The potential adverse consequences of subclinical hypothyroidism have been discussed in literatures. Findings. The prevalence of subclinical hypothyroidism has been reported to be between 4% and 20%. It varies as a function of sex, age, race, iodine intake, TSH cut-off value, and the presence of autoimmune thyroid disorders. Subjects with subclinical hypothyroidism may have no symptoms or mild hypothyroid or psychiatric symptoms. In long-term follow-up, subjects of subclinical hypothyroidism may remain in subclinical hypothyroidism, return to euthyroid, or progress to overt hypothyroid status. Subclinical hypothyroidism may provoke hypercholesterolemia, impair left ventricular diastolic and systolic function, alter other endothelial function, increase inflammatory markers, and thus increase the risk of atherosclerosis. Studies concerning the association between subclinical hypothyroidism and risks of cardiovascular disease and mortality have inconsistent results. Our recent study suggests that adult Taiwanese with subclinical hypothyroidism have increased risks for all-cause and cardiovascular mortality. Current guidelines suggest treating patients with TSH levels above 10 mU/L. Replacement therapy is not recommended for older patients with subclinical hypothyroidism and TSH between 4.5 and 10 mU/L. Conclusions. Evidence suggests that it is important to screen subclinical hypothyroidism in elderly. However, treatment of subclinical hypothyroidism should be individualized.

關鍵字

subclinical hypothyroidism ； cardiovascular disease ； mortality ； treatment