Careful Assessment of Maternal Thyroid Function Can Prevent Cases of Fetal Goitrous Hypothyroidism

Abstract

We feel that clarification is needed with regard to the maternal MMI therapy and thyroid status. First, MMI therapy was initiated upon discovery of a low fT4 level, no detectable thyroid antibodies, but suppressed TSH levels. We wonder what the reasons were for this treatment. The low fT4 level was not consistent with a diagnosis of hyperthyroidism (more likely hypothyroidism). The suppressed TSH found only 6 months after pregnancy could be a sign of postpartum thyroiditis defined by guidelines as ‘thyroid dysfunction within the first year postpartum’ (although this is almost always associated with antibody positivity) [2–4] . According to guidelines, such patients should not be treated with antithyroid drugs (ATD), but followed in order to detect a possible subsequent hypothyroid period. Even in cases of subclinical hyperthyroidism (low TSH, normal fT4), thyroid function tests should be repeated after 3–6 months to make sure that the TSH is persistently suppressed before considering treatment with ATD [5] . Unless the stated fT4 value is an error, the reported beneficial effect of MMI treatment is questionable, and we believe that the woman should not have been started on MMI therapy without further investigation. However, there are no details in the article of the woman’s symptoms or clinical findings beDear Editor, We read with interest the article ‘A rare case of recurrent fetal goiter’ by Kornacki et al. [1] . The authors report 2 cases of fetal goiter found in 2 consecutive pregnancies in the same woman. The first was discovered when the mother was 29 weeks pregnant and it led to an acute cesarean section and soon thereafter the death of the child because intubation was hindered by a large neck mass. Six months thereafter, the mother was started on methimazole (MMI) therapy (dose not communicated) after thyroid function tests had shown a TSH of <0.005 μIU/ml (normal range: 0.27–4.2 μIU/ml), free T4 (fT4) of 0.135 ng/dl (normal range: 0.932–1.71 ng/dl) and no detectable thyroid antibodies. One year after treatment start, she became pregnant again, and at 19 weeks of gestation a fetal goiter was discovered by ultrasound examination. Amniocentesis revealed hypothyroidism of the fetus, which was treated by a total of 8 intra-amniotic levothyroxine injections throughout the remaining pregnancy. With this treatment, the fetus became euthyroid with normal growth measurements and did not have any airway obstruction at delivery. The child was found to be hypothyroid 7 days later and was started on daily levothyroxine treatment. Received: January 31, 2013 Accepted after revision: February 21, 2013 Published online: June 10, 2013