Levothyroxine Therapy: Its Effect on Subclinical Hypothyroidism

Thyroid hormones are necessary for the desired development and growth of the fetus.There is an essential correlation between thyroid dysfunction in mothers and cognition in children; maternal hypothyroidism also affects reproductive functions, including fertility, abortions, and preterm birth.Due to regular changes in the metabolism of thyroid hormone and thyroid function, trimester-wise thyroid-stimulating hormone (TSH) levels and free thyroxine should be estimated.However, due to variations in age, ethnicity, and iodine intake, it is restricted to one population, which can be misleading to diagnose a euthyroid woman as a patient of hypothyroidism.Therapeutic benefits of levothyroxine remain unclear; however, when an intervention was made during the first trimester, it indicated a reduction of abortions and preterm delivery in women.The harmful effects of treatment with levothyroxine include hypertension, diabetes in pregnancy, and preeclampsia.Intervention with levothyroxine in the second trimester is of no use in reducing cognitive impairment.Thus, routine screening of subclinical hypothyroidism should be performed in all pregnant women to prevent its complications.Intervention with levothyroxine depends on the TSH levels, which vary according to trimester.Hence, the benefits of levothyroxine therapy depend upon the timing of intervention, change in the requirement of thyroxine during pregnancy, and alteration of dose of levothyroxine as required following delivery.