Goiter and pregnancy: a new insight into an old problem.

Evidence is presented that pregnancy constitutes a goitrogenic stimulus, particularly in conditions with a restricted or even a marginally low iodine intake. In a series of studies carried out in a large cohort of pregnancies in the Brussels area, the authors show that an increase in thyroid volume is observed in a majority of pregnant women, leading to goiter formation at delivery in 9% of the cases. Furthermore, increments in thyroid volume were correlated with biochemical evidences of functional stimulation of the thyroid, such as an elevation in serum TG levels, preferential T3 secretion, and slight increases in basal TSH at delivery. Hence, the association of biochemical features of thyroidal stimulation with volumetric changes in the gland strongly suggests that pregnancy truly induces goitrogenesis rather than vascular swelling ("intumescence") alone, at least in conditions with a low iodine intake. Finally, preliminary data from this laboratory, as well as recently published data from other investigators, suggest that goiter formation during pregnancy can easily be prevented by increasing the iodine supply during pregnancy.