085 - Tiroide e Gravidanza: Le risposte del laboratorio

E. Toffalori, P. Caciagli During pregnancy hormonal and metabolical variations occur and may determine a physiological modification of the thyroid functionality both in healthy women and those with thyroid pathology. Few weeks after conception, se- rum TBG increases two- to three-fold. This leads to an increase in the total amount of thyroid hormones of 1.5 times greater than pre-pregnancy values, since these hor mones sharply increase in the first weeks and plateau in the second trimester. There is now consensus that serum FT4 and FT3 levels decrease below the normal mean in the second and third trimesters. This decrease in free hormone is further amplified when the iodine nutrition status of the mother is restricted or deficient. Changes in FT4 concentrations during pregnancy are controversial and may be attributable to the diverse techniques used for measurement. In the first trimester of pregnancy the greatest concentra- tion of hCG occurs, which is associated to a decrease in serum TSH levels that may also reach 20%. The hCG ßsubunits has thyroid-stimulating activity since it becomes attached to the TSH receptor of the thyroid. This leads to an increase in iodide uptake, cAMP production and thyroid hormone secretion with a TSH decrease. The renal clearance of iodide increases and during pregnancy iodine intake should double. These changes can complicate the interpretation of maternal thyroid function tests, also because of the frequency of the sub-clinic thyroid disorders both in women and during pregnancy. In recent years several studies have demonstrated that the use of reference intervals of normal people for pregnant women leads to an underestimation of deficiencies in the maternal thyroid functionality with a high level of risk for both the mother and the neurological development of the fetus and child.