Abstract
Postpartum thyroiditis (PPT) has a prevalence of 1–22%, with an ~50% rate of evolution into permanent hypothyroidism (PH). PPT risk is assessed by measuring serum thyroid antibodies during gestation, as 1/3–1/2 of Ab+ve pregnant women will develop PPT. Family and personal history positive for autoimmune non-thyroid diseases (AINTDT), and consumption of swordfish increases while consumption of small oily fish decreases the risk of PPT. Monitoring thyroid function in a very high-risk subgroup avoids the costs of the Ab-based universal screening. We aimed at identifying such subgroup in 412 women followed from week 7–11 of gestation to month 12 postpartum. At study entry, we measured serum TPOAb, TgAb, TSH, FT4, FT3, and evaluated seafood consumption, familial history for thyroid diseases and AINTD, and personal history for AINTD. We measured TSH, FT4, FT3 at 1.5, 3, 6, and 12 months postpartum. PPT occurred in 63 women (15.3%), and PH in 34/63 (54%). Based on positivity/negativity for the three histories, women were classified into 8 categories, with PPT rates of 3.8–100%. Seafood consumption allowed further separation of subgroups having different PPT risks. We considered 11 possible strategies, termed [a] through [k]. Strategy [a] consisted in omitting gestational screening, while performing universal postpartum monitoring with TSH and one thyroid hormone; strategy [k] consisted in selective gestational screening with TPOAb and TgAb, based on history and fish consumption, and selective postpartum monitoring in TPOAb and/or TgAb+ve women. The 100% sensitivity, specificity and diagnostic accuracy of strategy [a] were counterbalanced by the highest costs (Euro 32,960 or 523 per each PPT caught). The corresponding numbers for strategy [k] were 78, 95, 93%, and Euro 8,920 or 182/PPT caught. These savings stem from gestational screening being done in 186 women, and postpartum monitoring done in 65/186 women. One gestational screning-free strategy was the cheapest (Euro 2,080 or 83/PPT caught), because based on postpartum monitoring of only 26 women, but had the lowest sensitivity (40%). Identification of pregnant women having different risks for PPT is feasible, with the costless evaluation of history and seafood consumption driving gestational screening of thyroid antibody status and postpartum monitoring of thyroid function.
Highlights
Postpartum thyroiditis (PPT) is a destructive autoimmune inflammation in women who did not have overt thyroid disease before pregnancy, and it has a prevalence of 1–22% depending on geographic area (1, 2)
Thyroid dysfunction can be biphasic or monophasic, with an ∼50% rate of no return to euthyroidism at the end of the 12th month postpartum, a condition termed permanent hypothyroidism (PH). (1, 2) If not evolved into PH, PPT tends to recur (1)
Concerning the understimated favoring role for development of PPT given by familial history of autoimmune non-thyroid disease (AINTD), in our study on a cohort of 412 women who were followed-up from week [7–11] of gestation through the end of the 12th month postpartum, (2) we found that the magnitude of risk conferred by familial history of AINTD (43/63 [68.2%] in the PPT group vs. 148/349 [42.4%] in the non-PPT group, P = 0.0002, OR = 2.92) was comparable to that conferred by personal history of AINTD (29/63[46.0%] vs. 80/349 [22.9%], P = 0.0001, OR = 2.87), and greater than that conferred by family history of thyroid disease (27/63 [42.9%] vs. 100/349 [28.7%], P = 0.025, OR = 1.87) (2)
Summary
Postpartum thyroiditis (PPT) is a destructive autoimmune inflammation in women who did not have overt thyroid disease before pregnancy, and it has a prevalence of 1–22% depending on geographic area (1, 2). Concerning the understimated favoring role for development of PPT given by familial history of AINTD, in our study on a cohort of 412 women who were followed-up from week [7–11] of gestation through the end of the 12th month postpartum, (2) we found that the magnitude of risk conferred by familial history of AINTD (43/63 [68.2%] in the PPT group vs 148/349 [42.4%] in the non-PPT group, P = 0.0002, OR = 2.92) was comparable to that conferred by personal history of AINTD (29/63[46.0%] vs 80/349 [22.9%], P = 0.0001, OR = 2.87), and greater than that conferred by family history of thyroid disease (27/63 [42.9%] vs 100/349 [28.7%], P = 0.025, OR = 1.87) (2). In that study, (5) which was based on universal screening by TPO and TgAb, the prevalence of PPT was 15.3%. This is the second highest frequency of PPT in Italy after the 22.1% found in Liguria, (6) this last prevalence matching the 22.3% of Wales (7)
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