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I am a pediatric endocrinologist from Oman I like to ask a bout the newborn baby who is born to first blood related cousin with a huge goiter measuring 5.5 by 3.5 cm .mum not on any goitergen drugs and she is not having in thyroid diseeases, her tft and thyroid titre are normal. The baby born by lscs , term apgar 10 & 10 at 1 &5 minutes.no evedence of upper air way obstruction , normal heart rate and normal physical examination. tft showed normal tsh and free t4 , thyroid scan showed grossly enlarged goiter with high uptake. My qeustion could this be thyroid dyshormogenesis? (because of goitre) If it is, why tft is normal.
Thanks,
Dr Aisha
Response
An enlarged thyroid gland in combination with a high radio-iodide (RI) uptake must be the result of hyperstimulation of the thyroid, either by TSH (permanent or transient), or by stimulating antibodies (transient), or due to autonomously activated tissue (permanent). In the presented case, only transient stimulation by TSH can explain the goitrogenesis, either prenatal, or perinatal, or both. In case of a newborn infant, thyroid hormonogenic action is not (yet) in a steady state. The plasma concentrations of TSH, (F)T4 and (F)T3 are changing rapidly in the first few days after birth. RI uptake percentage depends on thyroid size, TSH concentration and iodine state.
In neonates, the size of the thyroid is not a very good indicator of the severity of the underlying problem. In most newborn infants with a total iodide organification defect (due to inactivating mutations in the genes of TPO or DUOX2) the thyroid is only moderately enlarged, while the thyroid is unable to produce any T4 or T3. It is possibly the influence of maternal-fetal transfer of T4 that mitigates the growth of the gland. On the other hand I have seen een few patients with the Pendred syndrome, who were born with a large goiter (including airway obstruction) and had a normal thyroid function afterwards. In one of them we were able to measure TSH and FT4 immediately after birth and the following days, and we could demonstrate a strongly elevated TSH during several days that spontaneously decreased (kind of prolonged neonatal TSH surge). After normalisation of TSH the goiter gradually disappeared. The mother of this child was euthyroid.
Later on we studied a group of children with transient thyroidal CH with an abnormal response of the RI uptake after administration of perchlorate (partial iodide organification defect). Some children had mono-allelic mutations in the DUOX2 gene. In these children the thyroid gland was not enlarged at physical examination in the neonatal period. Neither they developed a goiter later on, as is the case in many patients with the Pendred syndrome, not treated with T4. In my opinion, the development of a goiter depends on individual associated conditions, like maternal FT4 level during pregnancy, placental characteristics, iodine supply, and the tendency of the thyroid to respond to TSH with an excessive bloodflow.
In conclusion, it is very likely that the young patient of consanguineous parents has one of the thyroid dyshormonogeneses. It must be a partial defect, either due to a mono-allelic or diallelic mutation. Candidate genes: PDS, DUOX2, TG, possibly TPO. Investigating the Pendred syndrome is important because of the association with (severe) sensorineural deafness, that can be missed by early postnatal hearing screening.
In case the CS is performed with use of iodine for disinfection, it is possible that this has influenced the thyroid condition.
Thomas Vulsma, MD