THYROID HORMONE RESISTANCE (THR) AND AUTOIMMUNE THYROIDITIS.

CHIESA ANA; MARTINEZ A; VIEITES A; RIVOLTA CARINA M.; TARGOVNIK HÉCTOR M.; GRUÑEIRO PAPENDIECK LAURA

Viña del Mar, República de Chile

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

Sociedad Latinoamericana de Endocrinología Pediátrica

THR is a dominantly inherited syndrome of reduced tissue responsiveness to thyroid hormone usually due to mutations in the T3 receptor beta gene. We describe a 17 year-old boy who was referred to our department at 4.7 years for short stature. He had a mild subvalvular aortic stenosis without cardiac insufficiency and celiac disease. He grew along the 3rd percentile up to age 11 years coping well with his grluten-free diet. At 14 years of age he entered puberty. At 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 mIU/l, T4 11 mg/dl, with positive antithyroid antibodies. With diagnosis of autoimmune thyroiditis he was treated with L-T4 100 mg/day. Growth improved but TSH levels failed to reduce in spite ofhigh T4 levels. (TSH 14 mIU/l, T4 13.5  mg/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 At the age of 17 with height at -1,96 SDS and complete sexual development, treatment was withdrawn and pituitary and peripheral tissue responses to graded doses of triidothyronine (LT3) were studied. 50, 100 and 200 mg/m2/day of LT3 inhibited basal TSH to 3,2 and 0.70 mIU/l, respectively. TRH/TSH test was still respondent under the higher dose and SHBG showed a paradoxical decrease. The patient became clinically hypothyroid. Molecular studies found a missense mutation in exon 9 of the TRb gnene (pN331D). Treatment with L-thyroxine was reinitiated with clinical improvement but TSH remained high. TRIAC 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.