[The management of hypothyroidism during pregnancy.].

During pregnancy, the need for thyroid hormone and its production increase: the presence of a concomitant thyroid disease, however, may prevent the maternal thyroid from meeting such increased demands for hormone production, which could lead to - or worsen - a state of hypothyroidism. Hypothyroidism in pregnancy could adversely affect the growth and development of the fetus as well as the course of the pregnancy itself. The present case report involves a 38-year-old woman with autoimmune hypothyroidism, who has been on levothyroxine replacement therapy since adolescence. The patient underwent the transfer of an embryo previously obtained by in vitro fertilization (Fivet), starting with pre-pregnancy TSH levels of 0.5 mU/L. Two weeks after the transfer, despite a preemptive increase in Euthyrox dosage once pregnancy was confirmed, TSH values rose to 7.6 mU/L, which is why the dose of levothyroxine was increased: after another two weeks, a new sampling showed the return of TSH to levels appropriate for pregnancy status (<2.5 mU/L). During the remainder of gestation, thyroid function was monitored regularly, with minor adjustments in levothyroxine dosage according to TSH values, with no further major swings in its levels until the end of pregnancy.