Transient Hypothyroidism in Infants Born to Mothers with Chronic Thyroiditis-A Nationwide Study of Twenty-three Cases.

Abstract

To define the difference in prognosis and the clinical features of transient neonatal hypothyroidism in infants born to mothers with chronic thyroiditis, we conducted a nationwide study of this condition. Sixteen mothers with chronic thyroiditis and twenty-three of their offspring with transient hypothyroidism were registered and reported in this paper. Five (group A) of twenty-two live infants showed physical, mental and/or psychomotor developmental delay (IQ below 80). No significant difference between TSH-binding inhibitor immunoglobulin (TBII) or thyroid-stimulation blocking antibody (TSBAb) activities in groups A and B (normal development) were noted. Moreover, there was no significant difference in thyroid function in the newborn period, ages at the start of thyroid medication or the dose and duration of treatment in the two groups. A striking difference observed between the two groups was the thyroid function of their mothers during pregnancy. In group A, four mothers were hypothyroid during pregnancy, and another mother discontinued thyroid medication in the last trimester and her baby was most delayed at the start thyroid medication. On the other hand, the mothers of only two of seventeen live cases in group B had mild hypothyroidism during pregnancy. There were two sets of siblings whose mother received inadequate treatment during the first pregnancy and adequate treatment during the second pregnancy. The psychomotor, physical and mental developmental delay were observed in their first babies. These findings suggested that maternal thyroid function during pregnancy might be an important factor in the prognosis of infants born to mothers with chronic thyroiditis.

Polychlorinated biphenyls (PCBs) exert thyroid hormone-like effects in the fetal rat brain but do not bind to thyroid hormone receptors.

“…This hypothesis is supported by the observation that the concentrations of PCBs, or of specific PCB congeners, in maternal and cord blood are associated with lower TH levels in both the mother and infant (Koopman-Esseboom et al 1994;Schantz et al 2003). Although several epidemiologic studies have failed to identify an association between TH and PCB body burden (Hagmar et al 2001;Longnecker et al 2000;Matsuura and Konishi 1990;Sala et al 2001;Steuerwald et al 2000), experimental studies consistently find that PCB exposure decreases circulating levels of thyroxine (T 4 ) in rats (Bastomsky 1974;Bastomsky et al 1976;Brouwer et al 1998). Therefore, it is possible that PCB body burden is negatively associated with serum TH levels in humans but that the variability inherent in human populations makes this association difficult to reveal.…”

Relation of severity of maternal hypothyroidism to cognitive development of offspring

“…[1][2][3][4] Pharoah et al 2 reported an inverse correlation of maternal thyroxine concentrations with cognitive development of the oVspring, but the relative contributions of maternal and fetal thyroid deficiencies are still unknown. Mental retardation can occur in endemic cretinism in the absence of postnatal hypothyroidism in the oVspring, but transient fetal hypothyroidism cannot be ruled out.…”

Clinical Courses and Thyroid Conditions in Three Infants Born to a Mother with Thyroid Stimulating-Blocking Antibodies.

“…There were no mothers whose thyroid function including TBII and/or TSBAb activities gradually improved with their clinical courses [6]. The measurement and follow-up study of TSBAb and/or TBII activities [9] are very important in plural pregnancies of a mother with these autoantibodies.…”

“…These three infants had different clinical courses. There are only a few papers on plural hypothyroid cases from a single mother with TSBAb [6]. Serum thyroid hormone, TSH levels, titers of thyroid autoantibodies and activities of thyrotropinreceptor antibodies in this mother and in these infants were studied and followed.…”