THYROID HORMONE RESISTANCE (THR) AND AUTOIMMUNE THYROIDITIS

CHIESA, ANA; MARTINEZ, A.; VIEITES, A.; RIVOLTA, CARINA MARCELA; TARGOVNIK, HÉCTOR MANUEL; GRUÑEIRO PAPENDIECK, LAURA

Viña del Mar

Congreso; XVIII Annual Meeting of the Sociedad Latinoamericana de Endocrinología Pediátrica (SLEP); 2006

Sociedad Latinoamericana de Endocrinología Pediátrica (SLEP)

THR is a dominantly inherited syndrome of reduced tissue responsiveness to thyroid hormone usually due to mutations in the T3 receplor beta gene. We describe a 17 year-old boy who was referred to our department atl 4.7 years for short stature. He had a mild subvalvular aortic stenosis wilhout cardiac insufficiency and celiac disease. He grew along the 3rd percentile up to age 1I years coping well with his gluten-free diet. Al 14 years of age he entered puberty. Al 14.5 years he grew poorly, (height -2.5 SDS) and a diffuse goiter was noted. Thyroid function was assessed and TSH levels were 26.7 mlU/l, T4 11 µg/dl, with positive antithyroid antibodies. With diagnosis of autoimmune thyroiditis he was treated with L-T. 100 µg day. Growth improved butl TSH levels failed to reduce in spite of high T4 levels. (TSH 14 mlU/I, T4 13.5 µg/dl, FT4  3.11 ng/dl). At the age of 17 with height at -1.96 SDS and complete sexual development, treatment was withdrawn and pituitary and peripheral tissue responses to graded doses of triiodothyronine (LT3) were studied. 50, 100 and 200 µg /m2/day of LT3 inhibited basal TSH to 3, 2 and 0.70 mlU/l, respectively. TRH/TSH test was still respondent under Ihe higher dose and SHBG showed a paradoxical decrease. The patient became clinically hypothyroid. Molecular sludies found a missense mutation in exon 9 of the TRb gene (pN331D). Treatment with L-thyroxine was reinitiated with clinical improvement but TSH remained high. TRlAC was added to treatment THR has to be considered in patients with high TSH and thyroid hormone levels even in the occurrence of autoimmune disorders.