In congenital hypothyroidism bone maturation at birth may be a predictive factor of psychomotor development during the first Year of life irrespective of other variables related to treatment.

Objective: To evaluate in a cohort of infants with congenital hypothyroidism (CH): (a) the frequency of bone maturation (BM) retardation at birth and (b) whether BM delay at birth may be considered as a tool to make a prognosis of psychomotor status at the age of 1 Year, irrespective of other variables related to treatment.

Design: BM at birth, CH severity and developmental quotient (DQ) at the age of 1 Year were retrospectively evaluated in 192 CH infants selected by the following inclusion criteria: (a) gestation age ranging between 38 and 42 weeks; (b) onset of therapy within the first Month of life; (c) initial thyroxine (l-T(4)) dosage ranging from 10 to 12 microg/kg/day; (d) normalization of serum thyrotropin (TSH) levels before the age of 3 Months; (e) Monthly adjustments of l-T(4) dose during the first Year of life with serum TSH levels ranging from 0.5 to 4 mIU/l; (f) no major diseases and/or physical handicaps associated with CH; (g) availability of both thyroid scanning and knee X-rays at the time of treatment initiation; (h) availability of DQ assessment at an average age of 12 Months.

Methods: BM was considered normal if the distal femur bony nucleus diameter exceeded 3 mm (group A) or retarded if either this nucleus was absent (subgroup B1) or its diameter was <3 mm (subgroup B2). DQ was evaluated with the Brunet-Lezine test.

Results: In 44.3% of cases BM was either delayed (23.5%) or severely delayed (20.8%). The risk of BM retardation was higher in the patients with athyreosis than in the remaining patients (41/57 vs 44/135, chi(2)=25.13, P<0.005). BM-retarded infants showed a more severe biochemical picture of CH at birth and a lower DQ at the age of one Year compared with the group A patients. If compared with infants of subgroup B2 those of subgroup B1 exhibited significantly lower T(4) levels at birth and a more frequent association with athyreosis (70.0 vs 30.0%; chi(2)=7.49, P<0.01), whereas DQ was superimposable in both subgroups.

Conclusions: (a) BM at birth is delayed in almost half of CH patients and (b) CH severity per se can affect DQ at the age of 1 Year irrespective of other variables related to therapy.