THE FIRST CASE OF ASSOCIATION BETWEEN POST PARTUM THYROIDITIS AND THYROID HORMONE RESISTANCE IN AN ITALIAN PATIENT SHOWING A NOVEL p.V283A THRB (THYROID HORMONE RECEPTOR BETA) MUTATION

Background: Post-partum thyroiditis (PPT) is characterized by the development of post-partum thyroid dysfunction which may occur up to 12 months after delivery. The syndrome usually presents with transient thyrotoxicosis, followed by transient hypothyroidism. The association of this condition with resistance to thyroid hormones (RTH) has never been described. Patient findings: In this report, we describe a 30 year-old patient affected by RTH due to a novel p.V283A THRB (thyroid hormone receptor β) heterozygous mutation in exon 8 which covers the ligand binding domain, never before described in literature. Polymorphism was excluded through screening of 100 healthy controls. Summary: She became pregnant twice (in 2008 and in 2009) and developed PPT after both deliveries. Indeed, 2 and 1 months after her first and second pregnancy respectively, she presented with severe endogenous thyrotoxicosis and concomitant suppressed TSH levels, which represents an unusual finding in patients affected by RTH. Other causes of hyperthyroidism were excluded. After the thyrotoxic phase, she became hypothyroid (TSH >75 mU/L and low FT4 and FT3 levels), and eventually returned to her usual "euthyroid" status. During the course of PPT, no specific treatment was required, except for β-blockers used to treat tachycardia during the thyrotoxic phase. Conclusions: We observed a unique case of a woman affected by RTH, due to a novel mutation V283A THRB, who experienced PPT with a severe thyrotoxic phase, after both her pregnancies. The association between RTH and PPT has never been reported in literature. In particular, the marked suppression of TSH occurring when levels of thyroid hormone are particularly elevated, is not a frequent condition during RTH.