ESPE Abstracts

Background: The cardinal feature of the resistance to thyroid hormone (RTH) is reduced responsiveness of target tissues to thyroid hormone action caused by thyroid hormone receptor β gene (THRB) mutations impairing hormone binding in the majority (90%) of cases. It results in elevated serum levels of free thyroxine (FT₄) and triiodothyronine (FT₃) associated with unsuppressed thyroid SH.

Objective and hypotheses: The aim of the study is presentation of rare syndrome resistance to hormones.

Results: A 11-year old female with Marfan-like phenotype was referred with clinical suspicion of hyperthyroidism. She appeared hyperkinetic, complained of palpitation persisted on beta adrenergic blocking agent, which was administered by her cardiologist. The current examination revealed a goiter, exophthalmos and tachycardia. The elevated serum levels of FT₄ and FT₃ coexisted with unsuppressed TSH. Well responsive TRH test excluded TSH secreting adenoma. A magnetic resonance imaging (MRI) study of the pituitary did not reveal any pathologic mass. In the presence of thyrotoxic signs her treatment with thiamazole was initiated before the final diagnosis of RTH. During the treatment the patient’s clinical state significantly improved, while the goiter was increasing in size. The final estimated gland volume based on ultrasonography was 40 ml. Ultrasonography revealed the hypoechoic foci up to 8 mm in diameter. The thyroid scintigraphy with Tc-99m showed excessive uptake with the total suppression of the background activity. The thyroid foci was biopsy-verified (FNAB), and classified in second category by the Bethesda System. Now patient was ordered bromocriptine with cardioselective beta-blocker.

Conclusion: The presented patient develops nodular goiter, which is the background to the thyroid cancer under the condition chronic overstimulation by TSH. The elevated cardiovascular risk in RTH, connected to the high levels of FT₃ and its influence on isoform THR alpha predominated in the heart. i) Primary and secondary hypothyroidism is more prevalent in patients who have received oncologic treatment than in healthy individuals. ii) The cytostatics, especially anthracycline and XRT have an effect on the development of primary hypothyroidism. iii) BMT in children has significant effect of development of hypothyroidism in course of AITD. iv) Cytostatic treatment and XRT contribute to development of potentially neoplastic thyroid nodules.