Table 1.
Characteristics of studies on the association between hypothyroidism and NAFLD.
| Reference | Country | Study design | Study sample (mean age; female, %) | Diagnosis of NAFLD | Definition of hypothyroidism | Adjusted factors | Quality |
|---|---|---|---|---|---|---|---|
| Bano et al. (52) | Netherlands | Cohort | 9,419 individuals (64.7 years; 56.5%) | Ultrasound | Subclinical hypothyroidism was defined as serum TSH > 4.0 mIU/L and FT4 levels within the reference range. Overt hypothyroidism was defined as serum TSH > 4.0 mIU/L and FT4 levels < 0.85 ng/dl | Age, sex, cohort, follow-up time, use of hypolipidemic drugs and cardiovascular | 9 |
| Chung et al. (12) | Korea | Cross-sectional | 4,648 individuals (48.6 ± 11.8; 62.4%) | Ultrasound | Subclinical hypothyroidism (TSH > 4.1 mIU/L; normal free T4 concentration); Overt hypothyroidism: fT4 level < 0.7 ng/dL | Some known risk factors of NAFLD | 8 |
| Lee et al. (44) | Korea | Cohort | 18,544 individuals (37.8 ± 5.7; 50%) | Ultrasound | Subclinical hypothyroidism (TSH > 4.2 mIU/L, normal fT4); overt hypothyroidism (TSH > 4.2 mIU/L, fT4 < 10.97 ng/dL) | Sex, age, BMI, TGs, and HDL | 9 |
| Pacifico et al. (45) | Italy | Cross-sectional | 402 individuals (6–16 years) | Ultrasound | Subclinical hypothyroidism (TSH > 4.1 mIU/L with normal FT4); overt hypothyroidism (TSH > 4.1 mIU/L with FT4 < 0.7 ng/dL) | Age, gender, pubertal status, and BMI-SDS (or WC) as well as FT3 and FT4 | 7 |
| Kaltenbach et al. (46) | Germany | Cross-sectional | 332 individuals including 99 NAFLD patients (14.1 ± 1.9; 33.3%) and 233 non-NAFLD subjects (13.9 ± 1.8; 58.8%) | Ultrasound | Subclinical hypothyroidism (TSH > 4 μU/mL, normal thyroxine) | Age, BMI-SDS, and stage of puberty | 7 |
| Liangpunsakul and Chalasani (47) | US | Case–control | 616 individuals (49 ± 13; 59%) | Enzymatic procedures | Overt hypothyroidism | Diabetes mellitus, hyperlipidemia, and hypertension | 7 |
| Pagadala et al. (13) | US | Case–control | 663 individuals (50.4; 56.2%) | Histological | Overt hypothyroidism | Gender, ethnicity, diabetes, HTN, hyperlipidemia, and hypothyoidism and mean (SD) | 7 |
| Parikh et al. (48) | Western India | Case–control | 800 individuals including 500 NAFLD patients (44.3 ± 3.2; 64.6%) and 300 controls (41.6 ± 3.89; 66%) | Ultrasound | Subclinical hypothyroidism (TSH > 5.5 IU/mL but <10 IU/mL) and overt hypothyroidism (TSH > 10 IU/mL) | Age, gender, alcohol use, and serum triglycerides | 7 |
| Xu et al. (49) | China | Case–control | 654 individuals including 327 subclinical hypothyroidism patients and 327 controls | Ultrasound | Subclinical hypothyroidism (TSH > 4.5 mIU/L; normal thyroxine level) | Waist circumference, systolic blood pressure, diastolic blood pressure, triglyceride, HDL cholesterol, and fasting plasma glucose | 7 |
| Posadas-Romero et al. (50) | Mexico | Cross-sectional | 753 individuals including 133 NAFLD cases and 620 controls (51.9; 63.9%) | Enzymatic procedures | Subclinical hypothyroidism (TSH > 4.5 mIU/L; normal thyroxine level) | None | 6 |
| Ittermann et al. (51) | Germany | Cross-sectional | 3,661 individuals | Ultrasound | Hypothyroidism was defined by increased serum TSH concentrations and decreased FT3 or FT4 concentrations | None | 6 |
| Eshraghian et al. (14) | Iran | Cross-sectional | 832 individuals including 127 NAFLD patients (48.2 ± 12.8) and 705 controls (36.9 ± 18.7) (61.3%) | Ultrasound | Subclinical hypothyroidism (TSH > 5.2 mIU/L, normal fT4); overt hypothyroidism (TSH > 5.2 mIU/L, fT4 < 11.5 ng/dL) | None | 6 |
| Wang and Zhao (53) | China | Cross-sectional | 806 individuals (56.99 ± 7.98; 81.3%) | Ultrasound | Subclinical hypothyroidism (TSH > 4.2 μUmL, FT4: 12–22) | None | 6 |