Catch-up in height and skeletal maturity in children on long-term treatment for hypothyroidism.

Abstract

Height and bone maturity have been followed for 9 years or more in 11 boys and 17 girls with primary hypo- or athyroidism. A marked catch-up in height carried the average patient from below the 3rd centile to above the 50th in 2 to 4 years of treatment in children treated before aged 2 — independently of the diagnosis hypo- or athyroidism. The catch-up only stabilized when the 75th centile was reached, at which point bone age had ceased to be retarded. The greater the height deficit at beginning of treatment, the greater the initial catch-up velocity. Final adult height averaged the 70th centile in girls and probably a little less in boys; every sufficiently treated child ended, or would certainly end, within normal limits. That catch-up may not always be complete, however, was shown by a pair of identical twins; the control twin reached the 90th centile as adult, while the treated twin reached the 70th. In children whose treatment started before age 1 the bone age became advanced over chronological age at about 3 years of age and remained advanced throughout childhood. This occurrence need cause no alarm provided the height centile is well above average. The bone age did not become advanced in children whose treatment started after aged 2. Hypothyroid infants show a marked reduction in rate of length growth from birth onwards and the diagnosis would be facilitated were accurate routine length measurements taken at birth and on subsequent clinic attendances.