Table 1.
Characteristics of included randomised controlled trials
| Study author (year) | Country | N | Intervention levothyroxine |
Comparator | Definition of subclinical hypothyroidism | Percentage of trial subjects with TPO antibody ≥50 IU/mL | Clinical outcomes |
| Casey et al 18 (2017) | USA | 677 | Treatment of subclinical hypothyroidism or hypothyroxinaemia | Placebo | TSH >3.00 then >4.00 mU/L and a normal free T4 | 33% | Childhood IQ and pregnancy outcomes |
| Nazarpour et al
20
(2018) |
Iran | 366 | Treatment of subclinical hypothyroidism | No treatment | TSH 2.5–10 mU/mL and a normal free thyroxine index | 0 | Pregnancy outcomes |
| Lazarus et al
19
(2012) |
UK and Italy | 794 | Thyroid screening plus treatment if criteria met | No treatment | TSH >97.5th centile and/or free T4 <2.5th centile | Not reported | Childhood IQ |
TPO, thyroid peroxidase; TSH, thyroid stimulating hormone; T4, thyroxine.