Table 1.
Characteristics of 10 included randomized controlled trials.
| Studies | Study design | Country (Ethnicity) | Participants (Number; Female, %; Mean age, years) | Hypertension (%) | TSH criteria for SCH (mIU/L) | Mean baseline TSH (mIU/L) | TSH testing method | L-T4 dosage (Mean or median dose, μg/day) | Treatment duration |
|---|---|---|---|---|---|---|---|---|---|
| Chen et al. (49) | RCT | China (Asians) | LT4 group (n = 43, 65.1%, 51) Placebo group: (n = 41, 65.9%, 56) |
LT4 group: 0%; Placebo group: 0% | >4.94 mIU/L | 8.36 | RIA | Increased from 12.5 μg daily until normal TSH (NA) | 24 weeks |
| Stott et al. (40) | RCT | European countries (Caucasians) | LT4 group (n = 368, 53.8%, 74.0) Placebo group: (n = 369, 53.7%, 74.8) |
LT4 group: 52.2%; Placebo group: 50.0% | >4.59 mIU/L | 6.41 | CIA | 50 μg daily or 25 μg daily in patients with weight <50 kg or coronary heart disease, with dose adjustment until normal TSH (50 μg/day) | 24 months |
| Zhao et al. (48) | RCT | China (Asians) | LT4 group (n = 210, 72.9%, 55.0) Control group: (n = 159, 73.6%, 55.4) |
LT4 group: Part; Control group: Part | 4.2–10 mIU/L | 5.96 | CIA | Increased from 25 μg daily until normal TSH (50 μg/day) | 15 months |
| Liu et al. (47) | RCT | China (Asians) | LT4 group (n = 60, 78.3%, 49) Placebo group: (n = 59, 76.3%, 49) |
LT4 group: 0%; Placebo group: 0% | 4.0–10 mIU/L | 6.2 | RIA | Increased from 12.5 μg daily until normal TSH (24.6 μg/day) | 48 weeks |
| Mainenti et al. (45) | RCT | Brazil (Mixed) | LT4 group (n = 11, 100%, 46.1) Control group: (n = 12, 100%, 44.1) |
LT4 group: Part; Control group: Part | >4.2 mIU/L | 7.5 | NA | Increased 0.75 μg/kg daily until normal TSH (42.25 μg/day) | 6 months |
| Nagasaki et al. (46) | RCT | Japan (Asians) | LT4 group (n = 48, 100%, 64.4) Placebo group: (n = 47, 100%, 66.0) |
LT4 group: NA; Placebo group: NA | >4.7 mIU/L | 7.32 | RIA | Increased from 12.5 μg daily until normal TSH (25.8 μg/day) | 5 months |
| Razvi et al. (44) | RCT | UK (Caucasians) | LT4 group (n = 50, 80.0%, 53.5) Placebo group: (n = 50, 84.0%, 54.2) |
LT4 group: 20.0%; Placebo group: 16.0% | >4.0 mIU/L | 5.4 | CIA | 100 μg daily until normal TSH (100 μg/day) | 12 weeks |
| Yazici et al. (43) | RCT | Turkey (Caucasians) | LT4 group (n = 23, 82.6%, 40.2) Placebo group: (n = 22, 86.4%, 39.7) |
LT4 group: NA; Placebo group: NA | >4.0 mIU/L | 8.47 | CIA | Increased from 50 μg daily until normal TSH (64 μg/day) | 12 months |
| Monzani et al. (42) | RCT | Italy (Caucasians) | LT4 group (n = 23, 82.2%, 37) Placebo group: (n = 22, 82.2%, 37) |
LT4 group: 0%; Placebo group: 0% | >3.6 mIU/L | 6.03 | RIA | Increased from 25 μg daily until normal TSH (70 μg/day) | 6 months |
| Monzani et al. (41) | RCT | Italy (Caucasians) | LT4 group (n = 10, 90.0%, 34.3) Placebo group: (n = 10, 90.0%, 29.2) |
LT4 group: 0%; Placebo group: 0% | >3.6 mIU/L | 5.44 | RIA | Increased from 50 μg daily until normal TSH (65 μg/day) | 6 months |
RCT, randomized controlled trial; LT4, L-thyroxine or levothyroxine; SD, standard deviation; TSH, thyroid-stimulating hormone; RIA, radioimmunoassay; CIA, chemiluminescent immunoassay; NA, data were not available in included studies. Hypertension was diagnosed by the previous diagnostic criteria of hypertension among those included studies.