Serum lipids in hypothyroid children: effect of disease and levothyroxine replacement therapy

Abstract

Hypothyroidism is associated with dislipidaemia and an increased risk of atherosclerosis. The aim of this study was to examine the effect of disease and long-term levothyroxine replacement therapy on serum lipids in hypothyroid children. We measured concentrations of total cholesterol, HDL-cholesterol LDL-cholesterol, triglycerides and thyroid-stimulating hormone in serum samples of 58 children with hypothyroidism (before and after therapy) and in 100 healthy controls. LDL-C and TC values were most markedly affected by the hypothyroid state. The values in the patients were on the average of 100% (LDL-C) and 54% (TC) higher than in the healthy controls. This finding is accordance with the known fact that LDL clearance is slower in hypothyroidism. TG concentrations were slightly higher (p lt 0.05) and HDL-C lower (p lt 0.02), but only in some age groups of patients. The effect of long-term L-T4 replacement on LDL-C and TC was quantitatively most pronounced. The values obtained in patients after therapy were markedly lower than before therapy and did not differ significantly from the values found in the corresponding age groups of healthy children. Significantly lower concentrations of HDL-C and TG after L-T4 administration were found only in children aged from 10 to 15 years. When we compared the lipid-lowering effect of L-T4 replacement therapy in normometabolic versus hypometabolic patients, we obtained a significantly greater effect on TC and LDL-C values in the normometabolic than in hypometabolic group (p lt 0.01). TC and LDL-C concentrations obtained in the L-T4 treated patients correlated well with the corresponding TSH levels (r = 0.770 and 0.725, respectively).

Hipotireoidizam je povezan sa dislipidemijom i povećanim rizikom od ateroskleroze. Cilj ovog rada je bio da se ispita uticaj bolesti i dugoročne supstitucione terapije levotiroksinom (L-T4) na lipidni status dece sa hipotireoidizmom. Određene su koncentracije ukupnog holesterola (TC) HDL-holesterola (HDL-C), LDL-holesterola (LDL-C), triglicerida (TG) i tireostimulirajućeg hormona (TSH) u uzorcima seruma sakupljenim od 58 dece sa hipotireoidizmom (pre i posle terapije) i 100 zdrave dece. Hipotireoidizam je najviše uticao na vrednosti LDL-C i TC: kod pacijenata su nađene prosečno 100% (LDL-C), odnosno 54% (TC) više koncentracije nego u kontrolnoj grupi. Ovo se slaže sa poznatom činjenicom da je katabolizam LDL čestica u hipotireoidizmu usporen. Vrednosti TG su bile nešto više (p lt 0,05), a HDL-C niže (p lt 0,02), ali samo u nekim starosnim grupama pacijenata. Dugoročna supstituciona terapija imala je najizrazitiji uticaj na nivoe LDL-C i TC: vrednosti dobijene kod pacijenata posle terapije bile su znatno niže nego pre terapije i nisu se značajno razlikovale od koncentracija dobijenih kod zdrave dece odgovarajuće starosti. Značajno niže vrednosti HDL-C i TG posle davanja L-T4 dobijene su jedino kod dece uzrasta od 10 do 15 godina. Sniženje vrednosti TC i LDL-C pod uticajem L-T4 bilo je izraženije kod normometaboličnih nego kod hipometaboličnih pacijenata (p lt 0,01). Kod pacijenata pod terapijom L-T4 dobijena je dobra korelacija između nivoa TC, odnosno LDL-C pacijenata sa koncentracijom TSH (r = 0,770 i 0,725, respektivno).