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Targeted screening for thyroid dysfunction during pregnancy misses many women with thyroid dysfunction
The background of the study. Subclinical hypothyroidism in pregnant women may be associated with adverse maternal and fetal effects, which has led to the suggestion that all pregnant women, or at least those at high risk for thyroid dysfunction, should be screened by measurement of serum thyrotropin (TSH). This study was done to determine the efficacy of screening pregnant women at increased risk for thyroid dysfunction, as compared with screening all pregnant women.
How the study was done. Serum TSH and free thyroxine (T4) were measured in 1560 consecutive pregnant women at the time of their first prenatal visit. The women were divided into high- or low-risk groups based on the presence or absence of a personal or family history of a thyroid disorder, or therapy for a thyroid disorder or a history of a nonthyroidal autoimmune disorder.
The results of the study. Among the 1560 women, 1399 (90 percent) had a normal serum TSH concentration, 40 (3 percent) a high concentration, and 121 (7 percent) a low concentration. The frequency of high concentrations was higher in the high-risk than in the low-risk women (7 percent vs. 1 percent), whereas the frequency of low concentrations was similar in the two groups.
The results in the high-risk women according to the individual risk factors are shown in the Table. All the factors were associated with an increase in the likelihood of a high serum TSH concentration, but not a low concentration.
| Table. Serum TSH Concentrations in 413 High-Risk Women According to Risk Factor. | ||||
| Risk Factor | No.* |
Normal |
High |
Low |
| Known thyroid disorder | 89 |
59(66%) |
17(19%) |
13(15%) |
| Taking T4 | 35 |
19(54%) |
8(23%) |
8(23%) |
| Nonthyroidal autoimmune disorder | 17 |
14(82%) |
2(12%) |
1(6%) |
| Thyroid disorder in family | 356 |
305(86%) |
20(56%) |
31(9%) |
| *Some women had more than one risk factor. | ||||
The conclusions of the study. A substantial proportion of pregnant women with abnormal serum TSH concentrations do not have risk factors for thyroid dysfunction, and therefore will be missed if only women with these risk factors are screened for thyroid dysfunction.
The original article. Vaidya B, Anthony S, Bilous M, Shields B, Drury J, Hutchison S, Bilous R. Detection of thyroid dysfunction in early pregnancy: universal screening or targeted high-risk case finding? J Clin Endocrinol Metab 2007;92:203-7.
Next Article: Bexarotene, a retinoic acid acid-like substance, inhibits thyrotropin secretion in normal subjects |
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| Thyroid Digest Index | | | March 2007 Thyroid Digest |
