The aim of the present study was to retrospectively re-evaluate a population of selected infants with congenital hypothyroidism (CH), in order to investigate whether sexual dimorphism affects: a) CH etiology; b) its biochemical severity at the time of screening and recall; c) patients' biochemical response to replacement treatment during the 1st yr of life; d) their bone maturation (BM) at birth; e) their psychomotor status at 1 yr. This retrospective study covers 192 infants (116 females) with persistent CH who were selected from a larger population of CH patients identified during a 10-yr period (1990-1999) by the screening programs of 5 northern, central, and southern regions of Italy. Thirty boys (39.5%) and 66 girls (56.9%) were found to have ectopia, whereas the remaining 46 boys and 50 girls exhibited the other causes of CH. When compared with the prevalence of the remaining causes that of ectopia was significantly higher in girls than in boys (66/116 vs 30/76; chi2=5.57, p<0.025), and sex ratio in ectopia was significantly different also compared with the orthotopic gland group only (66/84 vs 30/51; chi2=6.02, p<0.025). No differences between males and females were detected in the groups with either athyreosis or orthotopic gland. In no groups were there differences between sexes for gestational age, birth auxological data, percentage of newborns with bone retardation or developmental quotient at 1 yr. Thyroid tests at birth, age at TSH normalization and average thyroid tests under L-T4 treatment during the 1st yr did not differ between sexes in any of the groups.
Conclusions: a) in the Italian population sexual dimorphism affects pre-natal thyroid migration but neither biochemical severity of ectopia, nor pre-natal bone maturation and psychomotor development; b) girls with CH do not require higher doses of initial therapy in order to achieve TSH normalization; c) future developmental and molecular studies on ectopia etiology in CH need to take into account the effect of sexual dimorphism.