Congenital hypothyroidism presenting with reversible renal impairment: an under-recognised problem?

Abstract

Hypothyroidism with impairment of renal function and raised creatinine phosphokinase (CPK) is described in adults and children with acquired hypothyroidism, but not in congenital hypothyroidism. A male infant born at term weighing 3390g was seen aged 2months with prolonged jaundice. Examination showed somnolence, umbilical hernia, enlarged fontanelles and lower limb edema; length 55cm (-1.5 SD), weight 5.4kg (-0.13 SD). Biochemistry showed fT4 < 1pmol/L, TSH = 1044.36 μUI/mL, creatinine 77μmol/L(normal <35μmol/L), estimated glomerular filtration rate (GFR) 26ml/min/1.73m2, CPK 3952.5IU/L (normal<400IU/L). Ultrasound showed no thyroid tissue in the neck. In view of the renal impairment, peritoneal dialysis was initially contemplated but postponed and the child received levothyroxine 10μg/kg/day. Two months later thyroid function tests, CPK and renal function had all normalized with creatinine 19μmol/L and GFR 116ml/min/1.73m2. Reversible renal impairment is attributable to severe congenital hypothyroidism causing decreased myocardial contractility and cardiac output and to a direct effect on the kidneys. Thyroid function should be checked in infants with renal impairment of unknown cause. Cautious fluid management is indicated in hypothyroid infants. Hypothyroidism may also be associated with elevated serum CPK levels but resolves with thyroxin therapy.