Natural History of Subclinical Hypothyroidism with TSH ? 10 mIU/L: A Prospective Study
The risk of progression of subclinical hypothyroidism (SCH) to clinical dysfunction is one of the factors considered in the decision to treat this condition. This study evaluated the natural history of SCH in women with TSH ≤ 10 mIU/L.
Two hundred and fifty-two women with SCH and TSH levels ranging from 4.5 to 10 mIU/L were followed up for a period of 5 years.
Among the 241 patients followed up until completion of the study, 46 (19%) required levothyroxine (L-T4) therapy, 55 (22.8%) had spontaneous normalisation of serum TSH, and 140 (58.1%) continued to meet the criteria for mild SCH. In multivariate analysis, only initial TSH > 8 mIU/L was a predictor of the need for L-T4. In contrast, initial TSH ≤ 8 mIU/L and the absence of thyroiditis [negative anti-thyroid peroxidase antibodies (TPOAb) and ultrasonography (US)] were predictors of TSH normalisation. Of note, the natural history was similar in TPOAb-positive patients and patients with negative TPOAb but with positive US.
Most women with mild elevation of serum TSH, ranging from 4.5 to 10 mIU/L, do not progress to overthypothyroidism and even normalise their TSH. However, initial TSH seems to be a more important predictor of progression than the presence of antibodies or ultrasonographic appearance. This article is protected by copyright. All rights reserved.