ESPE Abstracts

Background: Levothyroxine monotherapy is the treatment of choice for congenital hypothyroidism (CH). Recently, it was reported that levothyroxine monotherapy cannot guarantee euthyroidism in all athyreotic adult patients. A more physiological treatment than levothyroxine monotherapy was suggested to be required in some patients with hypothyroidism.

Objective and hypotheses: To elucidate whether levothyroxine monotherapy is appropriate for all children with hypothyroidism. Levothyroxine monotherapy may not sustain physiological condition of thyroid hormones in some children with hypothyroidism.

Method: Serum thyroid hormones, free T₃ (pg/ml), free T₄ (pmol/l), TSH (mU/l), and free T₃:free T₄ ratio (pg/ml per pmol/l), were determined in a control group (n=54), a severe CH group (n=5), a mild CH group (n=18), and a pan-hypopituitarism (PHP) group (n=4). Free T₃:free T₄ ratios were also analysed with dosages of levothyroxine. A control group was hormonally examined only once, but each of the patients with hypothyroidism was frequently examined.

Results: Serum thyroid hormones were determined as; i) control: fT₃ 3.51±0.51, fT₄ 1.29±0.20, TSH 2.31±0.98, fT₃/fT₄ 2.78±0.56, ii) severe CH: fT₃ 3.78±0.60, fT₄ 1.64±0.32, TSH 2.52±2.02, fT₃:fT₄ 2.35±0.46, iii) mild CH: fT₃ 3.48±0.42, fT₄ 1.69±0.26, TSH 2.45±1.69, fT₃/fT₄ 2.11±0.38, iv) PHP: fT₃ 2.56±0.68, fT₄ 0.95±0.24, TSH 0.03±0.05, fT₃/fT₄ 2.86±1.06. Free T₄ levels of two CH groups were significantly higher than those of a control group. Free T₃:free T₄ ratios of two CH groups were significantly lower than that of a control group. Free T₃:free T₄ ratios of two CH groups were negatively correlated with dosages of levothyroxine.

Conclusion: This study suggested that levothyroxine monotherapy might maintain different conditions of peripheral thyroid hormones from physiological state in CH patients.