On their first antenatal visit (median 10th gestational week), 977 pregnant women in one district were assayed for TSH (IRMA, non-pregnant normal range 0,15-5 mIU/l) and TPO-Ab (RIA). Abnormal values were found in 154 women (15.8%): positive TPO-Ab in 92 (9.4%), TSH<0,15 in 35 (3.6%), TSH>5 in 49 (5.0%). Of them, 128 women were examined in our endocrine clinic (median 15th week), incl. thyroid ultrasonography (7.5 MHz, Doppler), and assayed for TSH, free T4, free T3, and antibodies against TPO, TG and TSH-receptor. Diagnoses of Graves disease (GD) and Hashimotos thyroiditis (HT) were evaluated, and treatment was started in those with confirmed abnormal thyroid function. Positive predictive values (PPV) of the screening abnormalities for these diagnoses and for treatment initiation were calculated.
No active GD was found. Suppressed TSH could always be explained by HCG surge in early pregnancy. In contrast, HT was found in 99/128 (69.5%) positively screened, suggesting ca. 11% prevalence in our pregnant population. L-thyroxine treatment was indicated in 46/128 (35.9%) positively screened, corresponding to ca. 5.7% prevalence. Of the screening parameters, TSH>5 was a good predictor both of HT (PPV 33/40=82.5%) and treatment indication (PPV 28/40=70%), while positive TPO-Ab were better predictor of HT (PPV 71/81=87.7%) but less perfect for treatment initiation (PPV 32/81=39.5%).
TSH (non-pregnant range) and TPO-Ab combined made a cheap and useful screening tool for HT and hypothyroidism detection, bringing 16% pregnant women for further evaluation, with a high yield of HT and hypothyroidism.
As in pregnancy TSH suppression is rarely caused by GD hyperthyroidism, and upper normal limit may be close to 2.5 mIU/l, our screening strategy may be modified labelling as positive those with TSH>2.5 and omitting those with TSH<0.15. Together with TPO-Ab, this would label positive 320 of our 977 pregnant women (32.8%).
The study has been approved by local Ethical Committee and supported by research project MZO 00179906.
01 - 05 Apr 2006
European Society of Endocrinology