Discussion
hypothyroidism, asphyxia, congenital hypothyroidism, prematurity, primary hypothyroidism, infertility, primary thyroid dysfunction, sepsis
HYPOTHYROIDISM, ASPHYXIA, CONGENITAL HYPOTHYROIDISM, PRIMARY HYPOTHYROIDISM, COMPLICATION, SYNDROME, SEPSIS, SUBCLINICAL HYPOTHYROIDISM, PERMANENT CONGENITAL HYPOTHYROIDISM
This prospective offspring cohort study examined neonatal screening TSH data of 57 newborns whose mothers received pre-conceptional OSCM HSG, finding no cases of transient subclinical hypothyroidism or permanent congenital hypothyroidism. This is reassuring and is consistent with studies from China (The only study that had previously shown an increased risk of primary hypothyroidism in newborns conceived following OSCM HSG was from Japan, where 2.4% of screened neonates (5/212) had an abnormal newborn screening result, and 0.94% (2/212) had primary hypothyroidism, noting that the background rate of congenital hypothyroidism in Japan is only 0.07% (The association of maternal iodine levels with newborn’s Day 7 thyroid function was an unexpected finding, suggesting that iodine excess might have a direct, long-term effect on fetal thyroid function or fetal thyroid hormone regulation. The possibility of low T3 syndrome was considered less likely because there were no risk factors in our cohort, such as prematurity, asphyxia, sepsis, or other factors predisposing to a sick euthyroid status. Interestingly, similar findings in the offspring of rats receiving comparable doses of excess iodine during pregnancy have recently been shown with low TSH and low normal FT4 and FT3 (Overall, primary thyroid dysfunction in newborns is not a complication following maternal OSCM HSG. However, some newborns, especially those exposed to higher levels of iodine, appear to have subtle changes in the hypothalamic-pituitary-thyroid axis, and further studies are required to confirm and assess whether these changes are present at older ages. There is also a possibity for transient fetal hypothyroidism from iodine excess, which recover by birth and could not have be assessed in the current study. For the above reasons, neurocognitive assessments of these children would be required to ascertain whether there are any long-term developmental issues.The main limitation of our study was the lack of a control population to compare the incidence of similar subtle changes in thyroid function. While our study population was not particularly large (57 newborns), it is difficult to prospectively study a larger number of offspring because pregnancy occurs only in a relatively small proportion of women who undergo HSG. Nonetheless, the present work is the only prospective investigation confirming normal neonatal thyroid status by serum thyroid function testing in the offspring conceived after OSCM HSG. Another key strength of this study was the availability of maternal parameters, allowing us to examine potential associations with offspring thyroid function and not performed in any previous studies. As there is widespread and growing popularity for the use of OSCM HSG as an infertility investigation and treatment modality, identifying the potential impacts of the associated iodine excess on the offspring is of clinical importance to inform specialists and infertile couples about the potential impacts of this intervention.