Thyroid dysfunction during pregnancy: when and whom to treat?

The thyroid gland is an important organ of the endocrine system. Its hormones influence all human organs and systems. Among thyroid dysfunctions, the most common variant is primary hypothyroidism. Since during pregnancy the mother's thyroid gland undergoes changes and the need for thyroid hormones increases, the risk of hypothyroidism increases. Particular attention should be paid to women who are carriers of antithyroid antibodies, as they are more likely to have thyroid dysfunction during pregnancy. In this regard, such patients should have their thyroid function examined in each trimester of pregnancy. It is known that hypothyroidism, both manifest and subclinical, has a negative impact on pregnancy outcomes and the subsequent psycho-physical development of the child. With obvious hypothyroidism, the risk of premature birth, arterial hypertension, preeclampsia and other complications increases. Therefore, treatment for hypothyroidism during pregnancy should begin immediately. The basis of treatment for this pathology is the prescription of replacement therapy with L-thyroxine immediately in a full replacement dose. For women who were already taking the drug before pregnancy, the dose of L-thyroxine increases by 20-30% with the onset of gestation. Also during pregnancy, there may be a decrease in thyroid hormones, usually thyroxine (T4w), with normal TSH. This condition is called isolated hypothyroxinemia. Its causes may be insufficient iodine intake, as well as increased levels of thyroxine-binding globulin. Its increase leads to an increase in the concentration of the total fractions of the hormones T4 and T3, but at the same time the true level of T4fr is underestimated. Isolated hypothyroidism does not require treatment if TSH levels are normal.