A confusing situation in the clinic practice: Isolated maternal hypothyroxinemia

Isolated maternal hypothyroxinemia (IMH) is a common problem in the clinic practice. There is a normal maternal thyroid stimulating hormone (TSH) level with a low maternal free thyroxine (FT4) level. The aim of this review is to explain IMH in the light of current literature and to contribute to clinicians in the management of IMH. Iodine deficiency is the most important factor in etiology. The effects of IMH on the pregnant women and the fetus are not clear. However, it is a serious concern among clinicians, especially considering the importance of the effect of thyroid hormones on fetal brain development. As for the treatment of IMH, the number of studies conducted is not sufficient and there is no consensus and evidence on levothyroxine treatment. However, there is a consensus on iodine supplementation and it is recommended to take 250 mg of iodine daily. As a result, IMH is a problem that should be taken seriously during pregnancy and care should be taken regarding its diagnosis and treatment. Additionally, more research is needed on the effects and treatment of IMH on pregnant women and fetal health.