title: [Combined l-thyroxine and l-triiodothyronine replacement therapy in congenital hypothyroidism].
abstract: BACKGROUND
  L-thyroxine replacement therapy is the treatment of choice for hypothyroidism. Recently, several studies suggested to complete it with l-triiodothyronine in acquired hypothyroidism.
  
  
  OBJECTIVE
  To study the role of combined l-thyroxine and l-triiodothyronine therapy in special cases with congenital hypothyroidism.
  
  
  METHODS
  Data of 16 patients (age: 11.9 ± 6.3 years; mean ± SD) are presented who had high serum free thyroxine values or even above the upper limit of reference range (21.16 ± 2.5 pmol/l) together with nonsuppressed TSH levels (15.7 ± 5.7 mIU/l), and therefore received l-triiodothyronine in completion (0.18 ± 0.09 μg/kg) once a day.
  
  
  RESULTS
  The combined replacement therapy resulted in a rapid improvement of the hormone parameters (TSH: 4.2 ± 3.15 mIU/l; free thyroxine: 16.55 ± 2.4 and free triiodothyronine: 7.4 ± 1.8 pmol/l). The efficiency of this combined therapy proved to be more evident (TSH: 4.33 ± 3.2 mIU/l; free thyroxine: 16.85 ± 3.1 and free triiodothyronine: 6.4 ± 0.85 pmol/l) in 10 patients treated for a longer period of time (duration of treatment: 2.9 ± 2.0 years). The dose of thyroxine substitution decreased from 2.6 ± 0.9 to 2.18 ± 0.6 μg/kg/day), the ratio of these hormones was between 5:1 and 19:1 and the quotient of free fractions was normalized (3.8 ± 0.4→2.6 ± 0.3) during the replacement therapy.
  
  
  CONCLUSIONS
  According to the observation of the authors a serious disturbance of feed-back mechanism may develop in some (>5%) children with congenital hypothyroidism (increased TSH release despite elevated free thyroxine level) after normal function of the feed-back system for years. Hormone parameters of these patients improve, then become normal on combined therapy supporting the rationale for this treatment method.
authors: Szent János Kórház és Észak-budai Egyesített Kórházai Budai Gyermekkórház részleg Budapest Bolyai u. 5-9. 1023. peter_f@budaigyk.hu
authors: Ferenc
authors: F
authors: Péter
authors: Agota
authors: A
authors: Muzsnai
mesh_terms: D003409:Congenital Hypothyroidism / Q000175:diagnosis / Q000188:drug therapy* / Q000453:epidemiology / Q000378:metabolism; D004359:Drug Therapy, Combination; D025461:Feedback, Physiological; D005260:Female; D020249:Hormone Replacement Therapy / Q000379:methods*; D006801:Humans; D006814:Hungary / Q000453:epidemiology; D007231:Infant, Newborn; D008297:Male; D012189:Retrospective Studies; D013960:Thyroid Function Tests; D013972:Thyrotropin / Q000097:blood / Q000378:metabolism*; D013974:Thyroxine / Q000627:therapeutic use*; D014284:Triiodothyronine / Q000627:therapeutic use*
chemical_list: D014284:Triiodothyronine; D013972:Thyrotropin; D013974:Thyroxine