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Thyroxine therapy has little benefit in patients with subclinical hypothyroidism
The background of the study. Subclinical hypothyroidism (high serum thyrotropin [TSH] and normal serum free thyroxine [T4] concentrations) is common, but whether treatment is beneficial is controversial. This report summarizes the results of studies of T4 treatment in patients with subclinical hypothyroidism.
How the study was done. Multiple databases of published articles were searched to identify randomized, controlled studies of the effects of T4 or placebo in patients with subclinical hypothyroidism. The primary outcomes were the effects of T4 and placebo on symptoms of hypothyroidism and quality of life. Secondary outcomes were changes in serum lipid concentrations, cardiac function, and bone mineral density.
The results of the study. Twelve studies meeting the inclusion criteria were identified. They included 350 patients, mostly adult women. Most had serum TSH concentrations <15 mU/L (highest, 55 mU/L). The doses of T4 ranged from 65 to 150 μg daily. The duration of the studies ranged from 6 to 14 months.
Serum TSH concentrations were lower at the end of T4 treatment, as compared with placebo, in the nine studies (335 patients) in which the results were reported. As shown in the Table, the results of analyses of the primary and secondary outcomes revealed little benefit of T4 therapy.
| Table. Results of T4 Therapy or Placebo in Patients with Subclinical Hypothyroidism. | ||||
| Outcome | Studies (no.) |
Patients (no.) |
Studies with Benefit of T4 (no.) |
Pooled Benefit of T4 |
| Symptoms of hypothyroidism | 7 |
289 |
1 |
No |
| Quality of life | 3 |
200 |
1* |
No |
| Serum cholesterol | 6 |
255 |
1 |
Yes |
| Serum LDL cholesterol | 4 |
188 |
1 |
No |
| Serum triglycerides | 5 |
221 |
0 |
No |
| Cardiac function | 4 |
132 |
6* |
NA† |
| Bone mineral density (L2–L4) | 2 |
47 |
0 |
No |
| *Results of multiple individual tests in several of the quality-of-life and cardiac-function studies. †Not analyzed. | ||||
The conclusions of the study. In patients with subclinical hypothyroidism, symptoms of hypothyroidism, quality of life, serum lipid concentrations, and cardiac function do not change more in response to T4 therapy, as compared with placebo.
The original article. Villar HC, Saconato H, Valente O, Atallah AN. Thyroid hormone replacement for subclinical hypothyroidism. Cochrane Database Syst Rev 2007;(3):CD003419.
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