OBJECTIVETo analyse the heritabilities of serum luteinizing hormone(LH), follicle-stimulating hormone (FSH), testosterone (T) and estradiol (E2) in twin boys, and to study the genetic contributions to gonadotropin-gonadal axis.

METHODSA total of 51 pairs of male twins, 35 monozygotic (MZ) and 16 dizygotic(DZ) aged 5 to 11 years, were investigated. Serum gonadotropin and sex hormone were measured by radioimmunoassay. The twin zygosity was verified by determination of short tandem repeat amplified fragment length polymorphism systems. The genetic analysis was performed using intraclass correlation coefficient method.

RESULTSThe intraclass correlation coefficient was greater in the MZ twins than in the DZ twins. The estimated heritabilities were respectively LH 0.51, FSH 0.32, T 0.81, E2 0.41.

CONCLUSIONGenetic factors are major determinants of gonadotropin-gonadal axis in boys.

Child ; Child, Preschool ; Gonadal Steroid Hormones ; blood ; Gonadotropins ; blood ; Humans ; Male ; Radioimmunoassay

Objective:To describe the differences in body mass index (BMI) distribution in adult twins registered in Chinese National Twin Registry (CNTR), and provide evidence for the risk factor analysis and prevention and control of overweight or obesity.Methods:A total of 32 725 twin pairs aged 18 years and above who completed the questionnaire survey during 2010-2018 and had complete registered information in CNTR and normal body weight and length were included in the analysis on the population and region specific distributions of BMI of twin pairs and the difference in BMI in twin pairs.Results:The twin pairs included in the analysis were aged (34.6±12.4) years, the twin pairs of same gender accounted for 79.7%. The average BMI was 22.5 kg/m 2. The overall prevalence of obesity and overweight was 4.9% and 23.7%, respectively. Participants who were men, 50-59 years old, married, had lower education level, and lived in northern China had higher overweight rate and obesity rate ( P<0.001). The difference in overweight or obesity prevalence between monozygotic (MZ) twin pars and dizygotic (DZ) twin pairs was not significant, but firstborn twin pairs had slightly higher rates of overweight and obesity than later-born twin pairs ( P<0.05). The analysis in same gender-twin pairs indicated that the difference in BMI was associated with age (trend test: P<0.001), and the difference was more obvious in DZ twin pair in MZ pair and this difference increased with age. The concordant rate of BMI was higher in MZ twin pairs than DZ twin pairs ( P<0.05). Conclusion:The distribution of BMI of twin pairs varied with population and region and BMI varied with age due to its genetic nature.