Background/Aims: Leptin is necessary for normal human pubertal development but its exact role in the period leading up to the onset of puberty has not been defined. This study has assessed the relationship between leptin and gonadotrophin secretion over time as children progress into puberty. Subjects and Methods: Twenty children (13 boys and 7 girls) judged to be close to the initiation of puberty were recruited. Three consecutive first morning urine samples were collected from each subject each month over 6 months. At the end of the study, the children were classified into those who remained physically prepubertal (n = 7) and those that had advanced in puberty (n = 13). Leptin and gonadotrophins were measured by immunoradiometric and immunofluorometric assay, respectively. Results: Total urinary leptin excreted over 6 months was higher in girls than in boys, both prepubertally and in early puberty, and in both sexes, was higher in those advancing into puberty than in those remaining prepubertal (girls 8.0 vs. 3.4 ng/l and boys 3.6 vs. 1.7 ng/l; both p < 0.05). In the whole group, when controlling for gender, there was a significant correlation between both leptin and luteinizing hormone (LH; r = 0.43, p < 0.001) and leptin and follicle-stimulating hormone (FSH; r = 0.32, p = 0.001). The possibility of a lead relationship was explored by pairing leptin values with the gonadotrophin values in the following month. Leptin was significantly correlated with FSH but not LH in both pre- and peripubertal children (prepubertal r = 0.45, p = 0.01; peripubertal r = 0.32, p = 0.01). Conclusions: This study has shown that in children approaching and progressing into puberty, leptin is associated with LH and FSH over the same time frame, and with FSH when leptin is acting as the lead hormone. These data imply that leptin is an important facilitator of the early phases of human puberty.

Because GnRH and its receptor (GnRHR) are pivotal regulators of the reproductive endocrine axis and mutations in GNRHR lead to hypogonadotropic hypogonadism, we investigated whether genetic variation in GNRHR or GNRH1 affects pubertal timing in the general population. To screen for missense mutations in these genes that might affect pubertal timing, we resequenced the coding regions of these genes in 48 probands with late but otherwise normal pubertal development. No missense variants were found in either gene, except for a previously identified single nucleotide polymorphism (SNP) in GNRH1 that was not associated with late pubertal development. To search for common variants that might affect pubertal timing, we took a haplotype-based association approach. To identify common haplotypes in these genes, we genotyped 41 SNPs in DNA from commercially available European-derived multigenerational pedigrees and participants in a multiethnic cohort (MEC). Two blocks of strong linkage disequilibrium were identified that spanned GNRHR and one was identified spanning GNRH1; within each block, more than 80% of chromosomes carried one of a few common haplotypes. A set of haplotype-tagging SNPs that mark these common haplotypes in all five ethnic groups within the MEC were defined and used to perform association studies among 125 trios (probands with late pubertal development and their parents) and 506 women from the MEC who had early (menarche< 11 yr of age, n = 216) or late (menarche > or = 15 yr of age, n = 290) pubertal development. Three SNPs in GNRHR showed modest association with late pubertal development in the trios; among the 506 women, a different SNP was associated with late menarche, and one rare haplotype was associated with early age of menarche. All of the observed associations were relatively modest and only nominally statistically significant; replication is needed to determine their validity. We conclude that genetic variation in GNRH1 and GNRHR is not likely to be a substantial modulator of pubertal timing in the general population.

Objectives: Constitutional delay of growth and puberty (CDGP) is a variant of normal pubertal timing and progress, often with dominant inheritance. It is likely that one or more genes will be associated with CDGP. Possible candidates are the leptin (L) and the leptin receptor (LR) genes, as the leptin axis links nutritional status to pubertal development. This study has assessed whether a) L or LR gene polymorphisms were associated with CDGP and b) the CDGP phenotype was influenced by these polymorphisms. Design: Case-control and transmission disequilibrium tests were used to test genetic association of L and LR polymorphisms with CDGP. Methods: We genotyped L (3 0 CTTT repeat) and LR polymorphisms (GlnOArg substitution, exon 6) in 81 CDGP children and 94 controls in the UK and 88 CDGP children from the US and assessed the effect of genotype on their anthropometric characteristics. Results: There was no association of these L or LR gene polymorphisms with CDGP. There was no difference in height or bone age delay within L or LR genotypes. However, UK CDGP children homozygous for the L short allele were heavier than heterozygotes and long allele homozygotes, with a similar trend in the US cohort. UK CDGP children with severe pubertal delay, who were thin, had significantly greater bone age delay and an increased frequency of parental pubertal delay than other groups and were less likely to be L short allele homozygotes. Conclusions: There was no association of specific L or LR polymorphisms with CDGP, but L short allele carriage influenced the phenotype within CDGP. 155 121-126 European Journal of Endocrinology

Zoladex-LA induces a significant reduction in gonadotrophins over 12 weeks. However, there are individuals, particularly those previously on Zoladex, in whom gonadotrophin suppression is waning by 12 weeks. As found with Zoladex, some children with precocious puberty treated with Zoladex-LA may require increased injection frequency, although correlation with clinical evidence of suppression needs to be studied further.