True precocious puberty associated with phenylketonuria.

We studied a girl with phenylketonuria who demonstrated signs of precocious puberty. At the age of 7.5 years she had premature telarche. Her height age was 7-9/12 years and her bone age was 9 years. Gonadotropin responses to LHRH administration were consistent with central precocious puberty. Elevated serum phenylalanine levels in this patient, due to poor compliance with the phenylalanine restricted diet, may be related to the early onset of puberty.