thyroid dysgenesis ( td ) refers to the developmental defects of the thyroid gland that 
 include aplasia , hypoplasia and ectopia , and accounts for majority of the cases of permanent 
 congenital hypothyroidism ( ch ) in iodine sufficient regions ( 1 ) . although most cases of td are sporadic , familial occurrence in about 2% , 
 higher prevalence in certain ethnic groups like hispanics and caucasians , and in babies with 
 down syndrome suggest the possibility of a role of genetic factors in some cases ( 1 , 2 ) . genetic 
 mutations known to be associated with td ( tshr , pax8 , nkx2 - 1 , foxe1 , nkx2- 5 and pax9 ) are , 
 however , detected in only 2% of all cases ( 2 ) . a 
 possible role of factors like sexual dimorphism , parental consanguinity and advanced 
 maternal age has also been proposed in some studies ( 3 , 4 ) . in the present study , we aimed to see 
 if gender and maternal age have an association with td in our patient cohort . a retrospective evaluation of medical records of patients with ch due to td followed up 
 between 2004 and 2014 in the pediatric endocrinology clinic of advanced pediatric center , 
 chandigarh located in northwest india , was performed . these children were referred from the 
 general outpatient department of the hospital after obtaining a thyroid profile for symptoms 
 suggestive of ch . data related to age at diagnosis , gender , parental age , family history , 
 thyroid scintigraphy , ultrasonography and thyroid hormonal levels were recorded . the 
 diagnosis of td was based on the findings of technetium-99 m pertechnetate 
 thyroid scintiscan and thyroid ultrasonograms done at the time of initial evaluation of ch . the diagnosis of hypothyroidism was based on low serum total t4 levels and elevated serum 
 tsh levels according to reference ranges ( 5 ) . those 
 having subclinical hypothyroidism , autoimmune thyroiditis or syndromic diagnosis like down 
 syndrome ( ds ) were excluded . maternal and paternal ages at the time of child birth were 
 determined by subtracting the child s age from the parental ages at the time of diagnosis . maternal ages were compared with the normative data presented in a previous indian study 
 ( 6 ) . the logistic regression analysis was performed to find out the independent predictive 
 ability of maternal age for the binary outcome of td . pearson s correlation was used to 
 analyse correlations among various quantitative study variables investigated . comparisons of 
 maternal ages with normative data were made by the student s independent t - test . all the statistical analyses were 
 performed on statistical package for social sciences ( spss inc . , complete information on thyroid scintigraphy and ultrasonography was available in 80 out of 
 310 children referred to our pediatric endocrinology clinic with a diagnosis of ch over the 
 study period . majority ( 63 , 78.7% ) had agenesis of thyroid gland followed by ectopic gland 
 in 12 ( 15% ) and hypoplasia in 5 ( 6.2% ) patients . in ultrasound , agenesis was detected in 70 
 ( 87.5% ) and ectopia and hypoplasia each in 5 ( 6.2% ) patients . there were 40 ( 50% ) boys and 
 40 ( 50% ) girls ( male to female ratio 1:1 ) . their mean age ( sd ) at diagnosis was 2.65 ( 2.81 ) yrs ( range 2 mo to 11 yrs ) . the mean initial total t4 and tsh concentrations in these children were 2.705  2.384 g / dl 
 ( range 0.018.9 ) and 293.48  289.81 mean maternal 
 age ( sd ) of 25.87 ( 4.17 ) yrs ( range 1935 yrs ) was significantly higher as compared with the 
 mean maternal age ( sd ) of 23.87 ( 3.34 ) yrs ( range 1839 yrs ) in a reference population ( p 
 < 0.0001 ) ( 6 ) . although majority ( 82.5% ) of mothers 
 were less than 30 yrs of age at the time of birth of the child with td , 17.5% were older 
 than 30 yrs as compared to only 6.1% in the cited reference ( table 1table 1age distribution of mothers of thyroid 
 dysgenesis patients as compared to a reference population * ) . odds of being older than 30 yrs were 3.23 times higher in mothers of children with td as 
 compared to mothers of normal children ( or 3.23 ; 95% ci : 1.546.44 ) ( p - value 0.0003 ) . this 
 gives an attributable fraction of 12% in population which means that 12% of td can be 
 eradicated by eliminating risk factor of older maternal age ( > 30 years ) at childbirth . however , the mean maternal age in the present study was lower than the mean maternal age 
 ( 27.8  5.4 yrs , range 1843 yrs ) of our cohort of children with thyroid dysfunction 
 associated with ds ( 7 ) . mean paternal age in our patients was similar to a reference population of a previous study 
 from india ( 29.60  4.33 yrs , range 2238 yrs versus 29.3  5.4 yrs , range 20.042.0 yrs , 
 p - value 0.65 ) ( 8) . the present study aimed to investigate the association of gender and maternal age with td , 
 the commonest cause of ch in our set up . no gender differences were observed in our patient 
 cohort similar to a previous study ( 4 ) . gender 
 differences have been suggested to modulate thyroid gland development during fetal period 
 probably involving molecular mechanisms ( 3 ) . the 
 higher prevalence of td in girls , however , has not been consistently reported ( 2 ) . these 
 findings are similar to a previous study in turkish patients ( 4 ) . although advanced maternal age is a risk factor for numerous maternal and 
 fetal conditions ( 9 ) , the reasons for its association 
 with td are presently unknown . age - related decreases in meiotic cohesins leading to 
 increased segregation errors and oocyte aneuploidy are associated with several congenital 
 birth defects ( 10 ) . however , oocyte aneuploidy does 
 not appear to be a factor in our study as children with chromosomal abnormalities were 
 excluded . in a previous study , it was proposed that advanced maternal age may increase the 
 risk of mutations in genes encoding some transcription factors associated with thyroid gland 
 development ( 4 ) . but acquisitions of intragenic 
 mutation are more frequently observed in the paternal allele , and the frequencies of the 
 events generally correlate with paternal age . in this context , further large studies are 
 required to confirm the observed association with advanced maternal age and then elucidate 
 the underlying mechanisms contributing to td . in conclusion , our study shows that advanced maternal age is more prevalent in children 
 with td and this may be one of the several risk factors associated with thyroid 
 developmental defects .
abstracta retrospective review of medical records of 80 children with thyroid dysgenesis ( td ) was 
 conducted to determine the association of gender and maternal age with td . 
 the study 
 subjects were attending the pediatric endocrinology clinic of our hospital which is a 
 large tertiary care multispecialty pediatric center located in chandigarh , northwest 
 india . 
 there were no gender differences ( boys to girls ratio 1:1 ) . 
 mean maternal age of 
 25.87  4.17 yrs ( range 1935 yrs ) was significantly higher as compared to the mean 
 maternal age of 23.87  3.34 yrs ( range 1839 yrs ) of a reference group ( p < 0.0001 ) . 
 odds of being older than 30 yrs were higher in mothers of children with td as compared to 
 mothers of normal children ( or 3.23 ; 95% ci : 1.546.44 ) ( p - value 0.0003 ) . in conclusion , 
 our data shows that advanced maternal age is more prevalent in children with td .