Pregnant women could benefit from screening for thyroid disease, research shows

Almost one woman in seven is known to test positive for antibodies to the enzyme thyroid peroxidase (TPO). TPO plays a major role in the production of thyroid hormones, and many women show an autoimmune response against the enzyme. Now a major study from the Charles University in Prague has found that 35% of the women who have TPO antibodies (TPOAb) in their blood go on to develop abnormal thyroid hormone levels within two years of giving birth, a symptom indicative of thyroid disease.

Antibodies to thyroid peroxidase (TPOAbs) are commonly found in the general population. 13.9% of adult females (and 2.8% of adult males) will test positive for TPOAbs. The significance of the presence of TPO antibodies has been widely discussed in recent years. The vast majority of women who test as positive for TPOAb will have otherwise normal thyroid functions, and will apparently remain healthy. However, previous studies showed that testing positive for TPOAb in pregnancy is linked to obstetric and thyroid problems in some women. Until now, the numbers of women affected has not been clear and follow-up studies of TPOAb+ women after delivery are scarce. However, Dr Eliska Potlukova and colleagues, working at the Charles University in Prague, has now linked the antibody to abnormal thyroid levels in many women after giving birth.

Dr Potlukova's team followed up 189 out of 822 women who had shown some form of thyroid disorder in the first trimester of pregnancy. One hundred of these women tested positive for the TPOAb antibody, but otherwise showed no thyroid problems. However, on retesting 22 months (on average) after delivery, 35% of these women showed abnormal levels (either raised or lowered) of thyroid stimulating hormone (TSH). TSH is produced in the pituitary gland, and it stimulates the thyroid gland to secrete the hormones thyroxine (T₄) and triiodothyronine (T₃). Thyroid hormones carry out a number of important roles in the body including regulating metabolic rate as well as heart and digestive functions, muscle control, brain development and bone maintenance. Incorrect levels of these hormones cause the medical conditions hypothyroidism, or hyperthyroidism.

Researcher Dr Eliska Potlukova said: "This is a potentially important finding, because it affects so many women. Roughly one in seven pregnant women will test positive for the TPOAb antibody, and we have now found that more than a third of these will go on to develop thyroid problems within two years of giving birth. This is rather surprising, as these positively screened women should have been referred to an endocrinologist already in pregnancy. Thus, in general population, this number would be much higher. That means a lot of women -- perhaps tens of thousands in one of the larger European countries -- who will have thyroid problems which could be detected earlier.

"We need to be following up these women to try to catch their thyroid disease early, as this could have major implications for the health of the mother, baby, and any subsequent babies who may be carried while the mother has a thyroid condition. In addition, we need to educate women to be aware that having this antibody can have serious health implications for themselves and their families."