Transient neonatal hypothyroidism

Severe transient postnatal hypothyroidism has been reported in infants whose mothers have received high doses of iodine during pregnancy or multiple local applications of povidone-iodine during pregnancy and for delivery (SED-14, 472). Transient neonatal hypothyroidism during breastfeeding after postnatal maternal topical iodine treatment has also been reported (68). 

Casteels K, Punt S, Bramswig J. Transient neonatal hypothyroidism during breastfeeding after post-natal maternal topical iodine treatment. Eur J Pediatr 2000 159(9) 716-717. 

Oide S, Yamaguchi H, Niizu N, Takahashi S, Takashima K. [Transient neonatal hypothyroidism probably due to contrast media used in fetal radiography.] Horumon To Rinsho 1983 31(Suppl) 76-9. 

Finally it is possible that part of the neuro-psychointeUectual deficit frequently resulting from prematurity could be due to unrecognized transient neonatal hypothyroidism. However, the role of a single factor is extremely difficult to isolate in such a multifactorial process. 

The evaluation of the iodine nutritional status was based on the determination of iodine concentrations in a large series of casual urine samples. 1 In 196 infants from the Brussels area, the median urinary iodine concentration was 4.8 iig/100 ml, 53% of the values being below 5 flg/dl. The urinary excretion of iodine was estimated as 51 lg/day.This in turn, enhances the susceptibility of the newborn, and particularly the premature to transient neonatal hypothyroidism.l ... 

Developmentally, thyroid hormones interact with sex hormones such that hypothyroidism prolongs the critical period for testosterone-induced defeminization (see below) [3] in contrast, the hyperthyroid state prematurely terminates the sensitivity to testosterone [3]. Undoubtedly, an important link in these and other effects is synapse formation. Hypothyroidism increases synaptic density, at least transiently [3]. Interesting parallels with synapse formation are reported for learning behavior in rats neonatal hypothyroidism impairs learning ability, whereas hyperthyroidism accelerates learning initially, followed by a decline later in life [3]. 

Neonatal hypothyroidism has been reported after maternal use of antithyroid drugs (106,107). Transient neonatal hyperthyroidism in a female child born to a mother who had been treated with potassium iodide and carbimazole during pregnancy was followed by sexual precocity (108). 

The determination of TSBAb is not routinely performed since the detection of TSBAb in hypothyroid women is exceptional. However, these antibodies can readily cross the placenta and result in transient fetal/neonatal hypothyroidism, with impaired neuromotor development (Matsuura and Konishi, 1990 Yasuda 1999). 

We do not know the reason for the varying degrees of fetal and neonatal hypothyroidism in the presence of uniform iodine deficiency in a given population, the frequency and the long-term consequences of transient fetal or neonatal hypothyroidism in endemic goiter and the possible role. 

Endocrine Prenatal, perinatal, or postnatal iodine overload can cause problems such as transient hyperthyrotropinemia, hypothyroidism, or hyperthyroidism in preterm and term infants [SED-15, 1896 SEDA-30, 279 SEDA-31, 411 SEDA-32, 440], Severe hypothyroidism in two term neonates resulted from iodine overload caused by postnatal use of an iodine-containing antiseptic [26 ]. One case was caused by excessive application of the antiseptic to the umbilicus and the other from maternal breast milk following the use of an iodine antiseptic by the mother for her episiotomy incision. 

Few countries in Europe are severely iodine deficient, but many, perhaps a majority, have a marginal iodine intake varying from 50 to 100 pg/day. The first world conference on neonatal thyroid screening held in Quebec in 1979 showed that, although the incidence of permanent sporadic congenital hypothyroidism in the newborn was similar in North America and in Europe, i.e. around 1/4000 live births, the incidence of transient primary hypothyroidism was almost six times higher in Europe... 

The first one is the observation that in areas with persisting borderline iodine deficiency, transient hypothyroidism in the newborns and also some anomalies of thyroid func on in pre iant women can still be linked to such an easily preventable factor as iodine deficiency. In some of these areas it is now clear that in screening, for neonatal hypothyroidism, roughly 2 out of 3 newborns rec alled for abnormal thyroid hormone or TSH levels are false positive. Apart from the psycholomcal and economic al costs linked to the rectal proc ess per-se, this transient hypothyroidism might induce around birth, brain maturation retardation of unknown long term... 

Screening for congenital hypothyroidism frequently shows transient abnormality of thyroid function. The newborn is very susceptible to iodide excess and in 70 % of the cases (1), the reason for transient hypothyroidism is iodine overload (2-3). A common cause may be X ray investigations with iodine products. Two newborns hospitalized in our Neonatal Intensive Unit presented with iodine overload from investigations, producing transient hypothyroidism. The hypothyroidism disappears with iodine elimination. In one case, the child were submitted at six months to another iodine overload without consequences. The thyroid tests show no change. Transient neonatal hyperthyrotropinemia may be due to iodine overload, and the search for its etiology is essential, because it allows one to stop the treatment. 

Weber G, Vigone MC, Rapa A, Bona G, Chiumello G. Neonatal transient hypothyroidism aetiological study. Italian Collaborative Study on Transient Hypothyroidism. Arch Dis Child Fetal Neonatal Ed 1998 79(l) F70-2. 

Iodine concentrations in breast milk and in random urine in neonates and the serum concentrations of neonatal TSH and free thyroxine on day 5 after delivery were measured after the use of povidone-iodine for disinfection after delivery (36). Iodine concentrations in the breast milk and neonatal TSH were significantly raised. Perinatal iodine exposure causes transient hypothyroidism in a significant number of neonates, in whom careful monitoring and follow-up of thyroid gland function are needed. It is better to avoid the use of iodine-containing antiseptics in pregnancy and neonates, especially if follow-up cannot be guaranteed. 

Serum TSH and thyroxine concentrations have been measured 57 days after birth in 365 healthy newborns whose umbilical stump had been treated with 10% povidone-iodine (41). The prevalence of high TSH concentrations was significantly higher in this group than in the general population (3.1% versus 0.4%), as was the rate of transient hypothyroidism (2.7% versus 0.25%). All the children were normal when retested 1 week later. Transient hypothyroidism due to skin contamination with povidone-iodine occurred in a neonate with an omphalocele (42). 

Giroux JD, Sizun J, Rubio S, Metz C, Montaud N, Guillois B, Alix D. Hypothyroldie transitoire apres opacification iodees des catheters epicutaneocaves au reanimation neonatale. [Transient hypothyroidism after iodine opacification of epicutaneo-caval catheters in neonatal intensive care.] Arch Fr Pediatr 1993 50 (3) 273. 

Neonates are particularly sensitive to the effects of iodine, and transient hypothyroidism has often been reported, particularly in pre-term infants (237,252,253). The low glomerular filtration rate in infants can also result in delayed excretion of contrast agents. 

Bona G, Zaffaroni M, Perona A. Neonatal transient hypothyroidism after excess iodide exposition by amnio-fetography. Panminerva Med 1988 30(3) 192-3. 

Perinatal iodine exposure causes transient hypothyroidism in a significant number of neonates, in whom careful monitoring and follow-up of thyroid gland function are needed. It is better to avoid the use of iodine-containing antiseptics in pregnancy and neonates, especially if follow-up cannot be guaranteed. 

The fetus and neonate are both at risk of developing iodine-induced hypothyroidism (Table 96.3). Many cases of such hypothyroidism in fetuses and neonates have been reported, especially in iodine-deficient regions of Europe, but also in iodine-sufficient areas. Iodide goiter in neonates is usually a transient problem. However, tracheal obstruction due to such goiter can be fatal (Markou et al, 2001 Wolff, 1969). Transient hypothyroidism without elevation of thyroid-stimulating hormone (TSH) in extremely... 

---