Table 1.
Biochemical criteria used to define isolated maternal hypothyroxinemia and its epidemiological impact.
| Author (reference number) (year) Country | Lower FT4 percentile (pmol/liter) | Manufacturer's FT4 reference range (pmol/liter) | Upper TSH limit (mU/liter) | Manufacturer's TSH reference range (mU/liter) | Prevalence of isolated hypo-thyroxinemia (%) | Gestational age of hypo-thyroxinemia assessment |
|---|---|---|---|---|---|---|
| Pop et al. [5] (1999) The Netherlands |
10th (1st tr. 10.4) |
8.8–18.0a | 2.0 | 0.15–2.0 | NR | |
| Pop et al. [6] (2003) The Netherlands |
10th (1st tr. 12.4) |
8.7–19.6a | 2.0 | 0.15–2.0 | NR | |
| Kooistra et al. [7] (2006) The Netherlands |
10th (NR) |
8.7–19.6a | 2.0 | 0.15–2.0 | NR | |
| Casey et al. [10] (2007) USA |
2.5th (GW 6-20 11.1) |
11.2–24.7b | 3.0 | NR | 1.3% | 1st half of gestation |
| Vaidya et al. [11] (2007) UK |
2.5th (1st tr. 10.6) |
12.0–23.0c | 3.0 | 0.27–4.2 | 1.6% (7.8%*) | 1st trimester |
| Cleary-Goldman et al. [13] (2008) USA |
2.5th (1st tr. 9.3; 2nd tr. 9.3) |
10.3–24.4b | 1st trim 4.28. 2nd trim. 3.93 | NR |
2.1% 2.3% |
1st trimester 2nd trimester |
| Moleti et al. [12] (2009) Italy |
2.5th (1st tr. 11.9; 2nd tr. 10.4; 3rd tr. 10.3) |
11.7–22.0d | 1st tr. 2.3 2nd tr. 2.8 3rd tr. 3.0 |
0.4–4.0 |
3.2% 12.7% 9.5% |
1st trimester 2nd trimester 3rd trimester |
| Berbel et al. [8] (2009) Spain |
10th (10.5) | 9.1–23.8e | 4.8 | 0.38–4.8 |
23.9% 20.6% 26.5% |
1st trimester 2nd trimester 3rd trimester |
| Shan et al. [14] (2009) China |
2.5th (GW 4 14.1 GW 8 11.9 GW 12 11.4 GW 16 12.3 GW 20 11.6) |
10.3–24.5b | GW 4 4.38 GW 8 3.8 GW 12 2.96 GW 16 3.29 GW 20 3.88 |
0.3–4.8 | 2.2% (0.4%*) | 1st half of gestation |
| Henrichs et al. [9] (2010) The Netherlands |
10th (11.76) 5th (10.96) |
11.0–25.0f | 2.5 | NR |
8.5% (<10th) 4.3% (<5th) |
GW 13 (median) |
*According to manufacturer's FT4 reference range; GW: gestational week; NR: not reported.
aEnhanced chemiluminescence immunoassay, Amerlite-MAB (Kodak Clinical Diagnostics, Amersham, UK); bchemiluminescent immunoassay, Immulite 2000 Analyzer (Diagnostic Products Corporation, Los Angeles, CA); celectrochemiluminescent immunoassay, Modular E 170 Analyzer (Roche Diagnostics Ltd., Lewes UK); delectrochemiluminescence immunoassay, Modular E 170 Analyzer (Roche Diagnostics GmbH, Mannheim, Germany); echemiluminiscence immunoassay, ADVIA Centaur-XP immunoassay system (Siemens Medical Solutions Diagnostics Ltd., Llamberis, UK); fenhanced chemiluminescent immunoassay, Vitros ECI Immunodiagnostic (ORTHO Clinical Diagnostics, Rochester, NY).