thyroid autoimmunity

Iron deficiency, thyroid autoimmunity occur frequently during pregnancy

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 Iron deficiency (ID) appears to be prevalent among pregnant women in their first trimester, occurring together with thyroid autoimmunity (TAI), higher thyroid-stimulating hormone (TSH), and lower free thyroxine (FT4) levels, a recent Belgian study finds.

Researchers tracked 1,900 pregnant women, collecting data on age, BMI, blood ferritin, thyroid peroxidase antibodies (TPOAb), as well as TSH and FT4 measurements. ID, TAI, and subclinical hypothyroidism (SCH) were defined as ferritin <15 ug/L, TPOAb >60 kIU/L, and TSH >2.5 mIU/L, respectively.

Of the participants, 35 percent had ID. TAI and SCH were more prevalent among pregnant women with ID compared to those who did not have ID (10 vs 6 percent; p=0.011; and 20 vs 16 percent; p=0.049, respectively).

Ferritin had an inverse relationship with TSH levels (p=0.001) and positive relationship with FT4 levels (p<0.001). In an adjusted analysis including potential confounders, ID remained associated with TAI (p=0.017). Meanwhile, the association between TAI and SCH disappeared in the logistic regression model (p=0.082), but remained present in the linear regression model (p=0.035).

Pregnant women need to increase daily iron intake by up to 3 times to produce more red blood cells, which will facilitate foetal and placental growth. Similarly, women in their first trimester should produce more thyroid hormones to aid full development of the babies’ brains as they have yet to develop thyroid glands of their own. ID and thyroid disorders may thus be detrimental, potentially leading to obstetrical and foetal complications.

The findings suggest that ID remains an important problem during pregnancy. It is important that women be checked for ID prior to and during pregnancy and take supplements to help minimise the risk of pregnancy complications, researchers said.

Additional research must be conducted to investigate whether higher rates of TAI, ID, or both have an influence on pregnancy outcomes.

Pregnant women with subclinical hypothyroidism more likely to miscarry

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Among pregnant women at low risk for thyroid dysfunction, the existence of subclinical hypothyroidism, thyroid autoimmunity or both prior to 8 weeks’ gestation increases the likelihood of miscarriage, according to recent findings.

In the prospective cohort study, researchers evaluated 3,315 women seen at the gynecology/obstetrics clinics of 13 hospitals and six prenatal clinics in three Chinese cities. The women were enrolled in the study between January and September of 2012 at the clinics, all of which were located in areas of China deemed iodine sufficient. Women identified for analysis were between 4 and 8 weeks’ gestation, and had lived in the area for more than 5 years.

Study participants completed questionnaires pertaining to demographic and obstetric history (maternal age, gestational age, previous pregnancies/births, and previous miscarriage). The questionnaires also elicited information about education level, income, smoking status, alcohol consumption, family history of thyroid disorders, history of type 1 diabetes, autoimmune diseases and treatments involving head or neck irradiation.

At baseline, all women were imaged by ultrasound to confirm ongoing pregnancy. The study’s primary outcome was miscarriage, which was characterized as sudden pregnancy loss before 20 weeks’ gestation. Participants underwent monthly thyroid function tests and ultrasound imaging at the clinics. The thyroid tests measured thyroid stimulating hormone, free thyroxine, thyroid peroxidase antibody, thyroglobulin antibody and urinary iodine.

On the basis of the thyroid test results, women were classified into four groups: euthyroidism (ET), isolated subclinical hypothyroidism (SCH), isolated thyroid autoimmunity (TAI) and subclinical hypothyroidism with TAI (SCH and TAI). Patients in the SCH cohort were further divided into two subgroups SCH1 and SCH2, based on TSH levels; as a result, the SCH and TAI group was also further stratified into two groups (SCH+TAI1 and SCH+TAI2).

The researchers found that compared with ET women (2.2%), those with SCH had a significantly higher risk of miscarriage (7.1%; adjusted OR=3.40; 95% CI: 1.62-7.15). Additionally, women with TAI alone were also at significantly increased risk of miscarriage (5.7%) vs. ET patients (2.2%; adjusted OR=2.71; 95% CI, 1.43-5.12), as were women in the TAI+SCH1 groups (10%; adjusted OR=4.96; 95% CI: 2.76-8.90) and the TAI+SCH2 groups (15.2%; adjusted OR=95% CI, 3.76-24.28).

Among 110 women who miscarried, the gestational ages were lower among those with subclinical thyroid disorders (11.3 weeks) vs. ET women (9.33 weeks; P =.024). The subgroup analysis also determined that higher TSH levels were associated with lower gestational age at miscarriage, in women with or without TAI.

The researchers said these findings may support the need to monitor thyroid function in pregnant women.

“To some extent, these finding support universal screening of women of reproductive age for thyroid function and thyroid autoimmunity early during pregnancy or during the preconception period,” the researchers wrote.