Subclinical hypothyroidism: the state of the art.

Subclinical hypothyroidism (SH) is a common clinical problem, particularly in adulthood and the elderly. Its prevalence is conditioned by several etiological and risk factors. The highest age- and sex-specific rates are in women over 60. SH may be associated with manifestations of mild thyroid failure, which may reverse under levothyroxine (L-T4) therapy. The risk of progression to overt hypothyroidism is distinctly higher in cases with underlying thyroid disease. A population routine screening is not generally recommended, but screening is encouraged in high-risk groups. L-T4 therapy may be indicated in subjects with TSH levels which are repeatedly and consistently elevated (>10 microIU/ml) and may be considered in those with TSH ranging between 4.5-5.5 and 10 microIU/ml, particularly if anti-thyroid antibodies are positive and/or hypothyroid symptoms are present. Treatment should be based, at least initially, on L-T4 low doses.