Which antithyroid drug for pregnancy

At present, the preferred choice of treatment after the first trimester of pregnancy remains uncertain [ 2 , 3 , 4 ]. The immunological changes during a pregnancy characterized by immunosuppression may attenuate the hyperthyroidism of GD and the indication for treatment and the dose of treatment should be carefully monitored with swift adjustments to meet the change in need.

Along with considerations on the type and severity of side effects, a shift in therapy may introduce a risk of less controlled hyperthyroidism. Clearly, more evidence is needed, and studies with detailed assessment of the type and timing of exposure are warranted to inform the clinical guidance on the when and how to treat maternal hyperthyroidism throughout the pregnancy [ 32 ]. Considering alternative treatments, a focus on the feasibility of using potassium iodide has emerged from studies in Japan [ 36 , 37 ].

In a cohort of pregnant women with GD, treatment had been switched from MMI to potassium iodide in early pregnancy due to intolerance to PTU [ 36 ]. These cases were retrospectively reviewed, and the prevalence of birth defects was evaluated according to treatment.

The authors speculated whether this finding was related to maternal thyroid function in early pregnancy [ 36 ]. A general concern about the use of iodine for the treatment of hyperthyroidism is that this treatment may be less effective than ATDs in the control of hyperthyroidism [ 6 ]. In a subsequent study from Japan [ 37 ], focus was on thyroid function in pregnant women who shifted from MMI to potassium iodide. From a clinical point, the identification of these patients is important considering the choice of treatment, but no specific predictors of this tendency to escape from the antithyroid effect of iodine could be identified in that study [ 37 ].

Further studies on the benefits and risks of treatment with potassium iodide in early pregnancy are needed including studies from populations with different levels of iodine intake. Another pertinent question is the possibility of other treatments or the development of new treatment. This perspective of alternative treatments on the one hand and the proposal of treatment withdrawal in early pregnancy on the other hand call for further research.

Clinical studies are needed and basic scientific work is important to support the clinical data and to develop our understanding of the mechanisms by which ATDs cause teratogenic side effects. Furthermore, different types of research serve to determine the role of maternal thyroid function and the role of the autoimmune mechanisms associated with the hyperthyroidism of GD.

MMI and PTU are considered to equally cross the placenta [ 38 ], to be equally effective in the control of hyperthyroidism in pregnancy [ 39 ] and to hold the same risk of inducing fetal hypothyroidism [ 40 ]. However, more evidence is needed to unveil the mechanisms underlying their teratogenic potential. Many possible mechanisms are in play, and one may also speculate on the possible interaction between ATD, maternal and fetal thyroid function, and thyroid autoimmunity and how these various exposures may have direct or indirect adverse effects.

Current evidence substantiates a risk of birth defects associated with the use of MMI and these malformations may be severe. On the other hand, further studies are needed to settle the teratogenic role of PTU and the role of maternal thyroid function and thyroid autoimmunity.

Detailed clinical data on the timing and type of exposure in early pregnancy are needed to inform clinical practice on the choice of treatment and the possibility of treatment withdrawal in selected patients. Furthermore, basic scientific work is important to address the mechanisms underlying the development of birth defects, and to precede the development of alternative or new treatments with less severe side effects.

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SLA conceptualized and drafted the manuscript. SA critically reviewed, discussed, and commented on the manuscript. September 17, [Epub ahead of print]. The two studies that showed an association between MMI use and birth defects included a much larger number of children exposed to MMI during the first trimester of pregnancy and children, respectively as compared to the four studies that found no association 73, , 30, and children, respectively.

In addition, the studies that found no association looked only for certain major birth defects and not the minor ones specifically associated with antithyroid drug use in the prior studies. The study that reported PTU-associated birth defects did not include more children as compared to the other studies children versus , , , , 52 children exposed to PTU, respectively ; however, this study evaluated children over a longer period of time, up to two years of age, while the other studies evaluated children up to maximum one year of age.

The PTU-associated birth defects were in general milder and diagnosed later when they resulted in complications, usually after one year of age. One of the two studies that showed an association between MMI use and birth defects recorded the thyroid function test results of the pregnant women and found no association between abnormal thyroid test results in early pregnancy and the development of birth defects. The studies that found no association between the use of antithyroid drugs in early pregnancy and birth defects in the offspring did not include enough subjects and did not follow the children for a long enough period of time to detect these abnormalities.

Introduction: Poorly treated or untreated maternal overt hyperthyroidism may affect pregnancy outcome. Fetal and neonatal hypo- or hyper-thyroidism and neonatal central hypothyroidism may complicate health issues during intrauterine and neonatal periods. Aim: To review articles related to appropriate management of hyperthyroidism during pregnancy and lactation. Methods: A literature review was performed using MEDLINE with the terms 'hyperthyroidism and pregnancy', 'antithyroid drugs and pregnancy', 'radioiodine and pregnancy', 'hyperthyroidism and lactation', and 'antithyroid drugs and lactation', both separately and in conjunction with the terms 'fetus' and 'maternal.