Identifying and treating subclinical thyroid dysfunction in pregnancy: emerging controversies

Abstract

Thyroid hormones are essential for an adequate growth and development of the fetus. In addition to the classical association between maternal hypothyroidism and neurological impairment in the progeny, other adverse reproductive events have been associated with maternal thyroid dysfunction including infertility, miscarriage and preterm delivery. Although all scientific societies endorse the treatment of overt hypothyroidism; the management and/or treatment of subclinical hypothyroidism, hypothyroxinemia or antithyroid antibody-positive women should be considered with caution. Important trials have found no clear benefit of treatment of subclinical hypothyroidism in terms of cognitive outcomes; however, other interventional studies appear to reduce some of the obstetric and perinatal complications. As a result, the dilemma between universal screening or selective screening of women at high risk of thyroid dysfunction during pregnancy remains unresolved. Despite this, levothyroxine is also now regularly prescribed by gynaecologists and centres for reproductive medicine. In this context, there is increasing concern regarding the risk of over diagnosis and subsequent potential overtreatment. Taken together, we need to reconsider how thyroid dysfunction should be identified in pregnant women and highlight the arguments for and against the use of levothyroxine in obstetric practices. Our main findings: the mismatch between the guidelines recommendations and the use of LT4 in clinical settings as well as the disparity of criteria between scientific societies from different medical specialties. In conclusion, it is essential to reach agreements between both endocrinologists and obstetricians.

Zebrafishduoxmutations provide a model for human congenital hypothyroidism

“…In humans, thyroid dysfunction during pregnancy has been positively associated with adverse maternal/foetal outcomes, including infertility, miscarriage, pre-eclampsia, pre-term (before 37weeks) birth and maternal thyroid dysfunction postpartum (Hernández et al, 2018;Stagnaro-Green et al, 2011;Velasco and Taylor, 2018).…”

Modern management of recurrent miscarriage

“…Data from non‐RM patients do suggest that for SCH diagnosed at TSH >4 mIU/L, thyroxine treatment could be beneficial. Current recommendations therefore support thyroxine for TSH >4 mIU/L but not at TSH of 2.5–4 mIU/L in the absence of thyroid antibodies . Consistent with this, the American Thyroid Association now advises using TSH >4 mIU/L …”

Effect of Thyroid Hormones on Neurons and Neurodevelopment

“…Whereas LT4 treatment is suggested in specific medical conditions when SH coexists with autoimmunity, there is no definite evidence of its efficacy in autoantibodies-negative patients in terms of positive effects on offspring neurodevelopment [62]. In fact, a randomized controlled trial comparing treated and untreated SH and hypotyroxinemic pregnant women did not reveal better cognitive outcomes in children belonging to either of the 2 groups [63].…”