Potential Consequences of Maternal Hypothyroidism on the Offspring: Evidence and Implications

Abstract

The adequate functioning of both the maternal and fetal thyroid glands plays important roles to ensure that the fetal neuropsychointellectual development progresses normally. Three sets of clinical disorders ought to be envisaged, potentially leading to impaired brain development: defective glandular ontogenesis (leading to congenital hypothyroidism), maternal hypothyroidism (usually related to chronic autoimmune thyroiditis), and finally iodine deficiency (affecting both the maternal and fetal thyroid functions). The present review will be focused mainly on maternal hypothyroidism, where both the severity and temporal occurrence of maternal thyroid underfunction drive the resulting repercussions for an impaired fetal neuronal development: such clinical situations may take place during early gestation (in women with known but untreated hypothyroidism) or appear only during later gestational stages (in women with thyroid antibodies, who remain euthyroid during the first half of gestation). Recent available evidence and its implications are discussed, as well as our present concepts relating to the complexities of the fetomaternal thyroid relationships, and the potential impact of maternal thyroid function abnormalities on the ideal offspring’s development.

Congenital hypothyroidism: the clinical profile of affected newborns identified by the Newborn Screening Program of the State of Minas Gerais, Brazil

“…O diagnóstico precoce e o tratamento iniciado nas primeiras semanas de vida são fundamentais para o desenvolvimento intelectual normal das crianças afetadas 1 A maioria das crianças afetadas apresenta sinais e sintomas bastante inespecíficos, e em apenas 5% delas é possível o diagnóstico através do exame clínico nos primeiros dias de vida 5,8 . A ausência ou reduzida aparência dos sintomas no iní-cio da vida podem ser explicadas pela passagem transplacentária de hormônio tireoidiano materno e por um aumento nos níveis cerebrais de deiodinase no recém-nascido 9,10 . No serviço, à primeira consulta, o exame físico foi sugestivo de hipotireoidismo em 55,3% das crianças avaliadas, por apresentarem mais de um sinal clínico da doença.…”

Expression of thyroid hormone receptors A and B in developing rat tissues; evidence for extensive posttranscriptional regulation

“…The beneficial effects of thyroid hormones on perinatal organ development and maturation are most readily recognizable in brain (Oppenheimer & Schwartz 1997, Morreale de Escobar et al 2004. However, since thyroid hormones can pass the placenta and accumulate in embryonic cells to functionally relevant concentrations well before the embryonic thyroid starts to function on its own (Morreale de Escobar et al 1990), thyroid hormone-dependent instructive effects in earlier phases of organ development are likely (Glinoer 2001, van Tuyl et al 2004). …”

Maternal Thyroid Function during Pregnancy and Puerperal Period

“…A study by Haddow et al [7] documented maternal thyroid deficiency during pregnancy and subsequent neuropsychological development of the child. Further studies highlighted the complex relations that exist between maternal thyroid deficiency during pregnancy and its possible consequences for the neuropsychointellectual development of the fetus and child [8,9]. Undiagnosed subclinical hypothyroidism in pregnant women is probably more prevalent than usually considered.…”