Plasma thyroxine levels in Duchenne muscular dystrophy.

Some young Duchenne muscular dystrophy (DMD) patients (3-7 years) had total thyroxine (T4) levels and T4 to thyroxine binding globulin (TBG) ratios above the normal range and significantly increased free thyroxine indices (fT4I) which, however, remained within the normal range. Older DMD patients (7-11 years) had T4 and TBG levels and fT4I similar to normal. In both DMD groups the thyroxine binding index (TBI) values were in the normal range.