Resistance to Thyroid Hormone Beta in a Patient Born to a Mother With Undiagnosed Graves' Disease

Resistance to Thyroid Hormone in a Boy with a Severe, Complex, Congenital Heart Defect (CHD) Requiring Multiple Cardiac Surgeries-Whether and How to Prepare Child for the Surgery

Background: Resistance to thyroid hormones (RTH) is a rare, genetically determined disease characterised by reduced tissue sensitivity to thyroid hormones (THs). It is caused by mutations in genes encoding the receptors for thyroid hormones, α (THRα) or β (THRβ), the distribution of which varies between tissues. Therefore, patients present with elevated TH levels with unsuppressed TSH levels, and symptoms of both hypothyroidism and hyperthyroidism may be present. Methods: Hence, we report the case of a boy with a complex, cyanotic, congenital heart defect who was also diagnosed with TH resistance syndrome. Results: Because of the clinical features of hyperthyroidism in preparation for cardiac surgery, thiamazole was administered, resulting in the normalisation of TH effects on the α-receptor for HTs. Due to the effectiveness of the proposed treatment, it was further introduced before the further stages of cardiac surgeries. Conclusions: The management of RTH is a constant challenge for clinicians and must be individualised.

Neonatal Graves disease with persistent hypoglycemia: A case report

Neonatal Graves disease is the most common cause of hyperthyroidism during the newborn period. Maternal Graves disease increases the risk of intrauterine growth restriction, small for gestational age, and neonatal Graves disease. Intrauterine growth restriction and small for gestational age are associated with hypoglycemia and transient neonatal hyperinsulinism. Neonatal Graves disease with severe persistent hypoglycemia has not been well described. We present the case of a female patient born at 34 weeks and 3 days with a birth weight of 1.6 kg (fifth percentile) to a mother with recent treatment for Graves disease. Prenatal ultrasounds were significant for intrauterine growth restriction and small for gestational age. The mother did not begin hyperthyroidism medical therapy until 23 weeks and 2 days of gestation. After the infant was born, the infant not only had symptoms of hyperthyroidism such as tachycardia and abnormal thyroid values but also had persistent hypoglycemia, which could be due to maternal propranolol usage, prematurity, IUGR, increased metabolism due to neonatal Graves, and transient stress-induced hyperinsulinism. The infant was started on methimazole for hyperthyroidism and propranolol for tachycardia. She was also started on diazoxide for persistent hypoglycemia. By 6 months of age, the hyperthyroidism and hypoglycemia had resolved. This is an interesting case of neonatal Graves disease with severe persistent hypoglycemia which we suspect is due to transient neonatal hyperinsulinism induced by multiple stress responses.

Effect of the Fetal THRB Genotype on the Placenta

CONTEXT

Pregnant women with mutations in the thyroid hormone receptor beta (THRB) gene expose their fetuses to high thyroid hormone (TH) levels shown to be detrimental to a normal fetus (NlFe) but not to an affected fetus (AfFe). However, no information is available about differences in placental TH regulators.

OBJECTIVE

To investigate whether there are differences in placentas associated with a NlFe compared with an AfFe, we had the unique opportunity to study placentas from 2 pregnancies of the same woman with THRB mutation G307D. One placenta supported a NlFe while the other an AfFe.

METHODS

Sections of placentas were collected and frozen at -80 °C after term delivery of a NlFe and an AfFe. Two placentas from healthy women of similar gestational age were also obtained. The fetal origin of the placental tissues was established by gDNA quantitation of genes on the X and Y chromosomes and THRB gene. Expression and enzymatic activity of deiodinases 2 and 3 were measured. Expression of following genes was also quantitated: MCT10, MCT8, LAT1, LAT2, THRB, THRA.

RESULTS

The placenta carrying the AfFe exhibited a significant reduction of deiodinase 2 and 3 activities as well as the expression of the TH transporters MCT10, LAT1 and LAT2, and THRA.

CONCLUSION

We present the first study of the effect of the fetal THRB genotype on the placenta. Though limited by virtue of the rarity of THRB mutations and sample availability, we show that the fetal THRB genotype influences the levels of TH regulators in the placenta.