Endocrine Abstracts

Thyroid hormone resistance (THR) is a rare dominantly inherited syndrome characterized by a reduced response of target tissues to thyroid hormone receptor. In most cases, THR is related to mutations in the thyroid hormone receptor beta gene (THRb). Management may be challenging in cases of gestation. Here we report the case of a pregnant patient with a possible not previously described mutation and negative genotype fetus.

Case report: Thirty-two year old patient asked for consultation for free T4 elevated levels (2.42, normal values: 0.93–1.7 ng/dl) with normal TSH values (3.6, normal values: 0.5–8.9 βUI/ml). Patient was asymptomatic and neither goiter nor thryoid autoinmunity was found. Genetic test detected in heterozygosis one variant of unknown significance in THRβ (c.737T > C (p. L246P). She was asked for family members with possible thyroidopathy and THR was also diagnosed in her father. He exhibits as well the same genetic variant. Patient got pregnant being TSH and free T4 levels 3.98 mUI/ml and 3.03 ng/dl respectively. As fetal DNA obtained by amniotic fluid ruled out that fetus was affected, treatment with PTU was started in order to mantain free T4 levels lower than 20% of the upper limit of normal. Fetal ecography showed normal fetal weight and free T4 levels were in desired range with doses of 200 mg/day PTU. Caesarean section was held 3 days before the estimated day of delivery due to prelabor rupture of membranes. Masculine infant born weighted 2760 grams and APGAR was 9/10/10.