Gestational thyroid function abnormalities in conditions of mild iodine deficiency: early screening versus continuous monitoring of maternal thyroid status.

OBJECTIVE: To longitudinally evaluate the timing of maternal thyroid underfunction occurrence in mildly iodine-deficient (ID) pregnant women, and ultimately assess the benefit of thyroid function testing at early gestation only in identifying maternal thyroid underfunction. PARTICIPANTS/METHODS: Serum free-thyroxine and TSH were measured in 220 consecutive women once in early pregnancy (by week 12) and twice per trimester subsequently. Anti-thyroperoxidase and anti-thyroglobulin were also determined at initial and final observation. RESULTS: Thyroid autoantibodies were detectable in 8.2% women. Overall, the prevalence of hypothyroidism over the course of gestation was 11.8% (26/220), with a relative risk of hypothyroidism in antibody-positive women of 5.0 (chi(2) 20.02, P<0.0005). Nonetheless, almost 70% hypothyroid women tested negative for thyroid autoantibodies. Fifteen/26 (57.7%) hypothyroid women were identified at presentation, and the remaining 11 at either early (6/11) or late (5/11) phases of the 2nd trimester. Isolated hypothyroxinemia was observed in 56/220 (25.4%) women, mostly from the 2nd trimester onwards. CONCLUSIONS: In mildly ID areas thyroid function testing early in gestation seems to be only partly effective in identifying thyroid underfunction in pregnant women. Indeed, in our series more than 40% hypothyroid women would not have been diagnosed had we limited our observation to early thyroid function tests alone. Although thyroid autoimmunity carried a 5-fold increased risk of hypothyroidism, iodine deficiency seems to be a major determinant in the occurrence of thyroid underfunction. Adequate iodine supplementation should be strongly recommended to meet the increased hormone demand over gestation.

Iodine prophylaxis using iodized salt and risk of maternal thyroid failure in conditions of mild iodine deficiency.

CONTEXT: Mild to moderate iodine deficiency during pregnancy can cause transient maternal hypothyroidism and impaired mental development of the progeny. These unfavorable effects are preventable by iodine supplementation. In Europe, however, less than 50% pregnant women receive iodine-containing supplements, thus representing dietary iodized salt the only carrier of iodine for most women in this life stage. OBJECTIVE/DESIGN: This longitudinal study is aimed to investigate the effects of long-term iodized salt consumption on maternal thyroid function during gestation. PARTICIPANTS/OUTCOME MEASURES: We prospectively evaluated thyroid function in 100 consecutive thyroperoxidase antibody-negative pregnant women from a mildly iodine-deficient area. Sixty-two women who had regularly used iodized salt for at least 2 yr prior to becoming pregnant and 38 who commenced iodized salt consumption upon becoming pregnant were classified as long-term (LT) and short-term (ST) iodine supplemented, respectively. RESULTS: Long-term iodized salt consumption resulted in a very low prevalence of maternal thyroid failure (MTF) in LT women. Conversely, short-term iodine prophylaxis does not seem to protect against the risk of MTF, the prevalence of which was almost 6-fold higher in ST than LT women (36.8% vs. 6.4%; chi(2) 14.7, P < 0.0005; relative risk 5.7, 95% confidence interval 2.03-16.08, P < 0.001). The relative risk reduction amounted to 82.5%, this measure indicating the extent to which long-term iodine prophylaxis using iodized salt would reduce the risk of MTF in ST women. CONCLUSIONS: Prolonged iodized salt significantly improves maternal thyroid economy and reduces the risk of maternal thyroid insufficiency during gestation, probably because of a nearly restoring intrathyroidal iodine stores.

Changes in both size and cytological features of thyroid nodule after levothyroxine treatment.

OBJECTIVE: We prospectively evaluated the effects of 12 months thyrotropin suppressive levo-thyroxine (L-T4) therapy in terms of changes in both thyroid nodule size and cytological features and considered whether thyroid nodule size changes actually resulted in (or were the result of) cytological changes. DESIGN AND PATIENTS: We studied 142 consecutive patients with benign 'cold' solitary thyroid nodules. For the purposes of the study, we divided our patients into three groups according to their initial cytological nodule classification as follows: group 1, including 88 colloid nodules (CN); group 2, including 30 hyperplastic nodules (HN); and group 3, including 24 adenomatous nodules (AN). MEASUREMENTS: The effects of TSH suppressive L-T4 treatment on both nodule volume and cytological characteristics were evaluated by ultrasonography and fine-needle aspiration (FNA) before and 12 months after the onset of therapy. RESULTS: Twelve months of TSH suppressive L-T4 treatment were effective in shrinking about one-third to one-quarter (31.8% CN, 26.7% HN and 25% AN) of thyroid nodules, irrespective of their initial cytological characteristics. Similarly, there was no difference in the prevalence of 'non-responders' (increasing nodules) to L-T4, which accounted for about one-fifth or less (20.5% CN, 13.3% HN and 20.8% AN) of all nodules. We found also that cytological features changed in 33.8% nodules after 12 months of L-T4 treatment. These changes were most commonly observed in HN and AN and consisted largely ( approximately 80%) of cytological characteristics resembling colloid features, not only in shrinking but also in stable nodules, thus indicating that cytology changes might be the very first indicator of nodule sensitivity to L-T4 therapy even in the continued absence of nodule shrinkage. When nodules were divided into three subgroups according to variations in size (shrinking, stable and increasing nodules), we observed that the distribution of the three cytological types showed a trend towards colloid lesions in shrinking nodules (chi2 3.8, P < 0.005) and towards an augmentation of hypercellular, adenomatous and suspicious characteristics in increasing nodules (chi2 3.6, P < 0.005). CONCLUSION: The frequency of shrinking nodules was not different between colloid, hyperplastic and adenomatous nodules. Repeat FNA should be advisable for thyroid nodules which increase in volume despite L-T4 therapy and might also provide useful information about nodule sensitivity to L-T4 treatment for both HN and AN, even where nodule size remains stable.