Polygenic susceptibility to testicular cancer: implications for personalised health care

BACKGROUND

The increasing incidence of testicular germ cell tumour (TGCT) combined with its strong heritable basis suggests that stratified screening for the early detection of TGCT may be clinically useful. We modelled the efficiency of such a personalised screening approach, based on genetic risk profiling in combination with other diagnostic tools.

METHODS

We compared the number of cases potentially detectable in the population under a number of screening models. The polygenic risk scoring (PRS) model was assumed to have a log-normal relative risk distribution across the 19 currently known TGCT susceptibility variants. The diagnostic performance of testicular biopsy and non-invasive semen analysis was also assessed, within a simulated combined screening programme.

RESULTS

The area under the curve for the TGCT PRS model was 0.72 with individuals in the top 1% of the PRS having a nine-fold increased TGCT risk compared with the population median. Results from population-screening simulations only achieved a maximal positive predictive value (PPV) of 60%, highlighting broader clinical factors that challenge such strategies, not least the rare nature of TGCT. In terms of future improvements, heritability estimates suggest that a significant number of additional genetic risk factors for TGCT remain to be discovered, identification of which would potentially yield improvement of the PPV to 80-90%.

CONCLUSIONS

While personalised screening models may offer enhanced TGCT risk discrimination, presently the case for population-level testing is not compelling. However, future advances, such as more routine generation of whole genome data is likely to alter the landscape. More targeted screening programs may plausibly then offer clinical benefit, particularly given the significant survivorship issues associated with the successful treatment of TGCT.

Human 3β-hydroxysteroid dehydrogenase deficiency seems to affect fertility but may not harbor a tumor risk: lesson from an experiment of nature

CONTEXT

3β-hydroxysteroid dehydrogenase deficiency (3βHSD) is a rare disorder of sexual development and steroidogenesis. There are two isozymes of 3βHSD, HSD3B1 and HSD3B2. Human mutations are known for the HSD3B2 gene which is expressed in the gonads and the adrenals. Little is known about testis histology, fertility and malignancy risk.

OBJECTIVE

To describe the molecular genetics, the steroid biochemistry, the (immuno-)histochemistry and the clinical implications of a loss-of-function HSD3B2 mutation.

METHODS

Biochemical, genetic and immunohistochemical investigations on human biomaterials.

RESULTS

A 46,XY boy presented at birth with severe undervirilization of the external genitalia. Steroid profiling showed low steroid production for mineralocorticoids, glucocorticoids and sex steroids with typical precursor metabolites for HSD3B2 deficiency. The genetic analysis of the HSD3B2 gene revealed a homozygous c.687del27 deletion. At pubertal age, he showed some virilization of the external genitalia and some sex steroid metabolites appeared likely through conversion of precursors secreted by the testis and converted by unaffected HSD3B1 in peripheral tissues. However, he also developed enlarged breasts through production of estrogens in the periphery. Testis histology in late puberty revealed primarily a Sertoli-cell-only pattern and only few tubules with arrested spermatogenesis, presence of few Leydig cells in stroma, but no neoplastic changes.

CONCLUSIONS

The testis with HSD3B2 deficiency due to the c.687del27 deletion does not express the defective protein. This patient is unlikely to be fertile and his risk for gonadal malignancy is low. Further studies are needed to obtain firm knowledge on malignancy risk for gonads harboring defects of androgen biosynthesis.

Pathogenesis of germ cell neoplasia in testicular dysgenesis and disorders of sex development

Development of human gonads is a sex-dimorphic process which evolved to produce sex-specific types of germ cells. The process of gonadal sex differentiation is directed by the action of the somatic cells and ultimately results in germ cells differentiating to become functional gametes through spermatogenesis or oogenesis. This tightly controlled process depends on the proper sequential expression of many genes and signalling pathways. Disturbances of this process can be manifested as a large spectrum of disorders, ranging from severe disorders of sex development (DSD) to - in the genetic male - mild reproductive problems within the testicular dysgenesis syndrome (TDS), with large overlap between the syndromes. These disorders carry an increased but variable risk of germ cell neoplasia. In this review, we discuss the pathogenesis of germ cell neoplasia associated with gonadal dysgenesis, especially in individuals with 46,XY DSD. We summarise knowledge concerning development and sex differentiation of human gonads, with focus on sex-dimorphic steps of germ cell maturation, including meiosis. We also briefly outline the histopathology of germ cell neoplasia in situ (GCNIS) and gonadoblastoma (GDB), which are essentially the same precursor lesion but with different morphological structure dependent upon the masculinisation of the somatic niche. To assess the risk of germ cell neoplasia in different types of DSD, we have performed a PubMed search and provide here a synthesis of the evidence from studies published since 2006. We present a model for pathogenesis of GCNIS/GDB in TDS/DSD, with the risk of malignancy determined by the presence of the testis-inducing Y chromosome and the degree of masculinisation. The associations between phenotype and the risk of neoplasia are likely further modulated in each individual by the constellation of the gene polymorphisms and environmental factors.

Diagnostic markers for germ cell neoplasms: from placental-like alkaline phosphatase to micro-RNAs

This concise review summarises tissue and serum markers useful for differential diagnosis of germ cell tumours (GCT), with focus on the most common testicular GCT (TGCT). GCT are characterised by phenotypic heterogeneity due to largely retained embryonic pluripotency and aberrant somatic differentiation. TGCT that occur in young men are divided into two main types, seminoma and nonseminoma, both derived from a pre-invasive germ cell neoplasia in situ (GCNIS), which originates from transformed foetal gonocytes. In severely dysgenetic gonads, a GCNIS-resembling lesion is called gonadoblastoma. GCT occur rarely in young children (infantile GCT) in whom the pathogenesis is different (no GCNIS/gonadoblastoma stage) but the histopathological features are similar to the adult GCT. The rare spermatocytic tumour of older men is derived from post-pubertal spermatogonia that clonally expand due to gain-of function mutations in survival-promoting genes (e.g. FGFR3, HRAS), thus this tumour has a different expression profile than GCNIS-derived TGCT. Clinically most informative immunohistochemical markers for GCT, except teratoma, are genes expressed in primordial germ cells/gonocytes and embryonic pluripotency-related factors, such as placental-like alkaline phosphatase (PLAP), OCT4 (POU5F1), NANOG, AP-2γ (TFAP2C) and LIN28, which are not expressed in normal adult germ cells. Some of these markers can also be used for immunocytochemistry to detect GCNIS or incipient tumours in semen samples. Gene expression in GCT is regulated in part by DNA and histone modifications, and the epigenetic profile of these tumours is characterised by genome-wide demethylation, except nonseminomas. In addition, a recently discovered mechanism of post-genomic gene expression regulation involves small non-coding RNAs, predominantly micro-RNA (miR). Testicular GCT display micro-RNA profiles similar to embryonic stem cells. Targeted miRNA-based blood tests for miR-371-3 and miR-367 clusters are currently under development and hold a great promise for the future. In some patients miR-based tests may be even more sensitive than the classical serum tumour markers, β -chorio-gonadotrophin (β-hCG), α-fetoprotein (AFP) and lactate dehydrogenase (LDH), which are currently used in the clinic. In summary, research advances have provided clinicians with a panel of molecular markers, which allow specific diagnosis of various subtypes of GCT and are very useful for early detection at the precursor stage and for monitoring of patients during the follow-up.

Abundance of DLK1, differential expression of CYP11B1, CYP21A2 and MC2R, and lack of INSL3 distinguish testicular adrenal rest tumours from Leydig cell tumours

OBJECTIVE

Testicular adrenal rest tumours (TARTs) are a common finding in patients with congenital adrenal hyperplasia (CAH). These tumours constitute a diagnostic and management conundrum and may lead to infertility. TART cells share many functional and morphological similarities with Leydig cells (LCs), and masses consisting of such cells are occasionally misclassified as malignant testicular tumours, which may lead to erroneous orchiectomy in these patients.

DESIGN

In this study, we aimed to investigate the potential of LC developmental markers and adrenal steroidogenic markers in the differential diagnosis of TARTs and malignant LC tumours (LCTs).

METHODS

We investigated mRNA and protein expression of testicular steroidogenic enzymes; CYP11A1 and HSD3B1/2, markers of adrenal steroidogenesis; CYP11B1, CYP21A2 and ACTH receptor/melanocortin 2 receptor (MC2R), and markers of LC maturation; and delta-like 1 homolog (DLK1) and insulin-like 3 (INSL3) in testicular biopsies with TART, orchiectomy specimens with LCTs and samples from human fetal adrenals.

RESULTS

Expression of testicular steroidogenic enzymes was observed in all specimens. All investigated adrenal steroidogenic markers were expressed in TART, and weak reactions for CYP11B1 and MC2R were observed at the protein level in LTCs. TART and fetal adrenals had identical expression profiles. DLK1 was highly expressed and INSL3 not detectable in TART, whereas INSL3 was highly expressed in LCTs.

CONCLUSIONS

The similar expression profiles in TART and fetal adrenals as well as the presence of classical markers of adrenal steroidogenesis lend support to the hypothesis that TART develops from a displaced adrenal cell type. Malignant LCTs seem to have lost DLK1 expression and do not resemble immature LCs. The different expression pattern of DLK1, INSL3 and most adrenocortical markers adds to the elucidation of the histogenesis of testicular interstitial tumours and may facilitate histopathological diagnosis.

A survey of Sertoli cell differentiation in men after gonadotropin suppression and in testicular cancer

It is widely held that the somatic cell population that is responsible for sperm development and output (Sertoli cells) is terminally differentiated and unmodifiable in adults. It is postulated, with little evidence, that Sertoli cells are not terminally differentiated in some phenotypes of infertility and testicular cancer. This study sought to compare markers of Sertoli cell differentiation in normospermic men, oligospermic men (undergoing gonadotropin suppression) and testicular carcinoma in situ (CIS) and seminoma samples. Confocal microscopy was used to assess the expression of markers of proliferation (PCNA and Ki67) and functional differentiation (androgen receptor). As additional markers of differentiation, the organization of Sertoli cell tight junction and associated proteins were assessed in specimens with carcinoma in situ. In normal men, Sertoli cells exhibited a differentiated phenotype (i.e., PCNA and Ki67 negative, androgen 40 receptor positive). However, after long-term gonadotropin suppression, 1.7 ± 0.6% of Sertoli cells exhibited PCNA reactivity associated with a diminished immunoreactivity in androgen receptor, suggesting an undifferentiated phenotype. Ki67-positive Sertoli cells were also observed. PCNA-positive Sertoli cells were never observed in tubules with carcinoma in situ, and only rarely observed adjacent to seminoma. Tight junction protein localization (claudin 11, JAM-A and ZO-1) was altered in CIS, with a reduction in JAM-A reactivity in Sertoli cells from tubules with CIS and the emergence of strong JAM-A reactivity in seminoma. These findings indicate that adult human Sertoli cells exhibit characteristics of an undifferentiated state in oligospermic men and patients with CIS and seminoma in the presence of germ cell neoplasia.

Pubertal onset in girls is strongly influenced by genetic variation affecting FSH action

Age at pubertal onset varies substantially in healthy girls. Although genetic factors are responsible for more than half of the phenotypic variation, only a small part has been attributed to specific genetic polymorphisms identified so far. Follicle-stimulating hormone (FSH) stimulates ovarian follicle maturation and estradiol synthesis which is responsible for breast development. We assessed the effect of three polymorphisms influencing FSH action on age at breast deveopment in a population-based cohort of 964 healthy girls. Girls homozygous for FSHR -29AA (reduced FSH receptor expression) entered puberty 7.4 (2.5–12.4) months later than carriers of the common variants FSHR -29GG+GA, p = 0.003. To our knowledge, this is the strongest genetic effect on age at pubertal onset in girls published to date.

Possible fetal determinants of male infertility

Although common reproductive problems, such as male infertility and testicular cancer, present in adult life, strong evidence exists that these reproductive disorders might have a fetal origin. The evidence is derived not only from large epidemiological studies that show birth-cohort effects with regard to testicular cancer, levels of testosterone and semen quality, but also from histopathological observations. Many infertile men have histological signs of testicular dysgenesis, including Sertoli-cell-only tubules, immature undifferentiated Sertoli cells, microliths and Leydig cell nodules. The most severe gonadal symptoms occur in patients with disorders of sexual development (DSDs) who have genetic mutations, in whom even sex reversal of individuals with a 46,XY DSD can occur. However, patients with severe DSDs might represent only a small proportion of DSD cases, with milder forms of testicular dysgenesis potentially induced by exposure to environmental and lifestyle factors. Interestingly, maternal smoking during pregnancy has a stronger effect on spermatogenesis than a man's own smoking. Other lifestyle factors such as alcohol consumption and obesity might also have a role. However, increasing indirect evidence exists that exposure to ubiquitous endocrine disrupting chemicals, present at measurable concentrations in individuals, might affect development of human fetal testis. If confirmed, health policies to prevent male reproductive problems should not only target adult men, but also pregnant women and their children.

Regulation of meiotic entry and gonadal sex differentiation in the human: normal and disrupted signaling

Meiosis is a unique type of cell division that is performed only by germ cells to form haploid gametes. The switch from mitosis to meiosis exhibits a distinct sex-specific difference in timing, with female germ cells entering meiosis during fetal development and male germ cells at puberty when spermatogenesis is initiated. During early fetal development, bipotential primordial germ cells migrate to the forming gonad where they remain sexually indifferent until the sex-specific differentiation of germ cells is initiated by cues from the somatic cells. This irreversible step in gonadal sex differentiation involves the initiation of meiosis in fetal ovaries and prevention of meiosis in the germ cells of fetal testes. During the last decade, major advances in the understanding of meiosis regulation have been accomplished, with the discovery of retinoic acid as an inducer of meiosis being the most prominent finding. Knowledge about the molecular mechanisms regulating meiosis signaling has mainly been established by studies in rodents, while this has not yet been extensively investigated in humans. In this review, the current knowledge about the regulation of meiosis signaling is summarized and placed in the context of fetal gonad development and germ cell differentiation, with emphasis on results obtained in humans. Furthermore, the consequences of dysregulated meiosis signaling in humans are briefly discussed in the context of selected pathologies, including testicular germ cell cancer and some forms of male infertility.

Patterns of DNA damage response in intracranial germ cell tumors versus glioblastomas reflect cell of origin rather than brain environment: implications for the anti-tumor barrier concept and treatment

The DNA damage response (DDR) machinery becomes commonly activated in response to oncogenes and during early stages of development of solid malignancies, with an exception of testicular germ cell tumors (TGCTs). The active DDR signaling evokes cell death or senescence but this anti-tumor barrier can be breached by defects in DDR factors, such as the ATM-Chk2-p53 pathway, thereby allowing tumor progression. The DDR barrier is strongly activated in brain tumors, particularly gliomas, due to oxidative damage and replication stress. Here, we took advantage of rare human primary intracranial germ cell tumors (PIGCTs), to address the roles of cell-intrinsic factors including cell of origin, versus local tissue environment, in the constitutive DDR activation in vivo. Immunohistochemical analysis of 7 biomarkers on a series of 21 PIGCTs (germinomas and other subtypes), 20 normal brain specimens and 20 glioblastomas, revealed the following: i) The overall DDR signaling (γH2AX) and activation of the ATM-Chk2-p53 pathway were very low among the PIGCTs, reminiscent of TGCTs, and contrasting sharply with strong DDR activation in glioblastomas; ii) Except for one case of embryonal carcinoma, there were no clear aberrations in the ATM-Chk2-p53 pathway components among the PIGCT cohort; iii) Subsets of PIGCTs showed unusual cytosolic localization of Chk2 and/or ATM. Collectively, these results show that PIGCTs mimic the DDR activation patterns of their gonadal germ cell tumor counterparts, rather than the brain tumors with which they share the tissue environment. Hence cell-intrinsic factors and cell of origin dictate the extent of DDR barrier activation and also the ensuing pressure to select for DDR defects. Our data provide conceptually important insights into the role of DNA damage checkpoints in intracranial tumorigenesis, with implications for the differential biological responses of diverse tumor types to endogenous stress as well as to genotoxic treatments such as ionizing radiation or chemotherapy.

Associations of filaggrin gene loss-of-function variants with urinary phthalate metabolites and testicular function in young Danish Men

BACKGROUND

Filaggrin is an epidermal protein that is crucial for skin barrier function. Up to 10% of Europeans and 5% of Asians carry at least one null allele in the filaggrin gene (FLG). Reduced expression of filaggrin in carriers of the null allele is associated with facilitated transfer of allergens across the epidermis. We hypothesized that these individuals may have increased transdermal uptake of endocrine disruptors, including phthalates.

OBJECTIVES

We investigated urinary excretion of phthalate metabolites and testicular function in young men with and without FLG loss-of-function variants in a cross-sectional study of 861 young men from the general Danish population.

METHODS

All men were genotyped for FLG R501X, 2282del4, and R2447X loss-of-function variants. We measured urinary concentrations of 14 phthalate metabolites and serum levels of reproductive hormones. We also evaluated semen quality.

RESULTS

Sixty-five men (7.5%) carried at least one FLG-null allele. FLG-null carriers had significantly higher urinary concentrations of several phthalate metabolites, including a 33% higher concentration of MnBP (mono-n-butyl phthalate; 95% CI: 16, 51%). FLG-null variants were not significantly associated with reproductive hormones or semen quality parameters.

CONCLUSION

This study provides evidence that carriers of FLG loss-of-function alleles may have higher internal exposure to phthalates, possibly due to increased transepidermal absorption. FLG loss-of-function variants may indicate susceptible populations for which special attention to transepidermal absorption of chemicals and medication may be warranted.

Characterization of the testicular, epididymal and endocrine phenotypes in the Leuven Vdr-deficient mouse model: targeting estrogen signalling

Vitamin D is a key factor for calcium and bone homeostasis, but signalling through the vitamin D receptor (VDR) seems also to be important for testicular function. To test the functional role of vitamin D signalling we examined the male reproductive system of the Leuven Vdr-ablated (Vdr(-/-)) mice, previously established as a model for hereditary vitamin D-resistant rickets. We investigated reproductive hormones, changes in gene expression and histological phenotype of eleven Vdr(-/-), eight Vdr(+/-) and nine Vdr(+/+) mice. Testicular and epididymal histology were grossly normal in Vdr(-/-) mice. Accordingly, no differences were found in serum concentrations of testosterone, estradiol, LH, and FSH or testicular expression of Cyp19a1, Ersα, Cyp17a1, Star, Insl3, Inhbb, and Amh. However, a significantly lower ERβ expression was found in testis of Vdr(+/-) and Vdr(-/-) mice, conversely epididymal expressions of ERα and the estrogen-target gene Aqp9 were higher. In conclusion, vitamin D seems dispensable for murine spermatogenesis and sex hormone production, but aberrant estrogen-signalling may elicit some of the VDR-mediated effects on male reproduction.

Influence of vitamin D on cisplatin sensitivity in testicular germ cell cancer-derived cell lines and in a NTera2 xenograft model

The active form of vitamin D, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) has anti-proliferative, pro-apoptotic, and pro-differentiating effects in somatic cancer cells in vitro and in vivo. 1,25(OH)2D3 also augments the anti-tumor effects of several chemotherapeutic agents, including cisplatin, which may have clinical relevance. Given the pro-differentiation effect of vitamin D recently demonstrated in testicular germ cell tumors (TGCTs), we hypothesized that 1,25(OH)2D3 could be a beneficial adjunctive to existing chemotherapy regime used to treat these tumors. In this study, cell survival effects of 1,25(OH)2D3, another pro-differentiation compound, retinoic acid and cisplatin were investigated in TGCT-derived cell lines in vitro. 1,25(OH)2D3 augmented the effect of cisplatin in an embryonal carcinoma-derived cell line (NTera2), possibly through downregulation of pluripotency genes and simultaneous upregulation of the cell cycle regulators p21, p27, p53, p73 and FOXO1, while no significant effects were found in TCam-2 and 2102Ep cell lines (derived from seminoma and embryonal carcinoma, respectively). Anti-tumor effects of cholecalciferol, 1,25(OH)2D3, and cisplatin were subsequently tested in vivo, in a NTera2 xenograft tumor model in nude mice. In xenograft tumors, co-treatment with 1,25(OH)2D3 and cisplatin resulted in downregulation of OCT4 and simultaneous upregulation of p21 and p73, but did not reduce tumor growth significantly more than cisplatin alone. Also, cholecalciferol supplemented diet (1100IU daily) after tumor formation did not increase cisplatin sensitivity in vivo. In conclusion, addition of 1,25(OH)2D3 augmented the antitumor effect of cisplatin monotherapy in vitro, but not in this in vivo testicular germ cell cancer model. Future studies are needed to investigate potential beneficial effects of vitamin D with lower cisplatin doses, and to determine whether 1,25(OH)2D3 may increase cisplatin sensitivity in chemotherapy-resistant TGCTs. This article is part of a Special Issue entitled 'Vitamin D Workshop'.

Molecular characteristics of malignant ovarian germ cell tumors and comparison with testicular counterparts: implications for pathogenesis

This review focuses on the molecular characteristics and development of rare malignant ovarian germ cell tumors (mOGCTs). We provide an overview of the genomic aberrations assessed by ploidy, cytogenetic banding, and comparative genomic hybridization. We summarize and discuss the transcriptome profiles of mRNA and microRNA (miRNA), and biomarkers (DNA methylation, gene mutation, individual protein expression) for each mOGCT histological subtype. Parallels between the origin of mOGCT and their male counterpart testicular GCT (TGCT) are discussed from the perspective of germ cell development, endocrinological influences, and pathogenesis, as is the GCT origin in patients with disorders of sex development. Integrated molecular profiles of the 3 main histological subtypes, dysgerminoma (DG), yolk sac tumor (YST), and immature teratoma (IT), are presented. DGs show genomic aberrations comparable to TGCT. In contrast, the genome profiles of YST and IT are different both from each other and from DG/TGCT. Differences between DG and YST are underlined by their miRNA/mRNA expression patterns, suggesting preferential involvement of the WNT/β-catenin and TGF-β/bone morphogenetic protein signaling pathways among YSTs. Characteristic protein expression patterns are observed in DG, YST and IT. We propose that mOGCT develop through different developmental pathways, including one that is likely shared with TGCT and involves insufficient sexual differentiation of the germ cell niche. The molecular features of the mOGCTs underline their similarity to pluripotent precursor cells (primordial germ cells, PGCs) and other stem cells. This similarity combined with the process of ovary development, explain why mOGCTs present so early in life, and with greater histological complexity, than most somatic solid tumors.

Identification of a novel androgen receptor mutation in a family with multiple components compatible with the testicular dysgenesis syndrome

CONTEXT

Androgen signaling via the androgen receptor (AR) is essential for normal testis development and male reproductive functions. We describe a rare family with 3 males affected by a mild disorder of sex determination compatible with testicular dysgenesis syndrome (TDS), including subfertility, cryptorchidism, hypospadias, and testicular cancer, caused by a novel AR mutation.

OBJECTIVE

The aim of this study was to describe the phenotype of the affected males, characterize functionally the novel AR mutation, and discuss the significance of partial androgen insufficiency in the pathogenesis of TDS.

PARTICIPANTS

The proband, his first cousin, and a nephew underwent a detailed clinical investigation including genetic tests, whereas four female members of the family were tested for the specific AR mutation.

RESULTS

A novel AR mutation, c.2214T>G;p.Ile738Met, was identified in the affected family members. Functional analysis of the mutation in a gene-reporter assay showed a 50% reduction in AR-induced transcriptional activity. The affected males had elevated LH and T in accordance with decreased AR signaling. The histology and immunohistochemical profile of the testis tissue from the 2 patients with testicular cancer showed features consistent with insufficient testis development and TDS.

CONCLUSION

The presence of all hallmarks of TDS, including germ cell cancer, in a family with a novel AR mutation causing a partial decrease in AR function is in line with the concept that reduced androgen signaling may contribute to the development of TDS. It also seems consistent with the hypothesis that environmental factors interfering with this pathway can play a role in the pathogenesis of TDS.

Androgen receptor CAG repeat length is associated with body fat and serum SHBG in boys: a prospective cohort study

BACKGROUND

Longer androgen receptor gene CAG trinucleotide repeats, AR (CAG)n, have been associated with reduced sensitivity of the androgen receptor (AR) in vitro as well as in humans. Furthermore, short AR (CAG)n have been associated with premature adrenarche.

OBJECTIVE

The aim of the study was to evaluate associations between the AR (CAG)n polymorphism and development of pubic hair, levels of androgens, and body fat content in healthy boys.

METHODS

A longitudinal study of 78 healthy boys (age 6.2-12.4 years at inclusion) from the COPENHAGEN Puberty Study was conducted with clinical examinations and blood samples drawn every 6 months. The AR (CAG)n length was established by direct DNA sequencing and reproductive hormones were measured in serum by standardized analyses.

RESULTS

Median AR (CAG)n length was 22 (range, 17-30). Before puberty (at 10 years of age), boys with long CAG repeats (CAG ≥ 24) had lower levels of SHBG (88 vs 125 nmol/L) (P < .05) and a nonsignificant trend toward higher median skinfold thickness (41 vs 31 mm) (P = .06) compared with boys with an average number of CAG repeats (CAG 21-23). In contrast, the inverse association was observed at puberty (at 12 years of age) in boys with short CAG repeats (CAG 17-20) (P < .05). Serum levels of LH and testosterone (at 12 years) were significantly higher in boys with long CAG repeats compared with boys with an average number of CAG repeats (P = .05).

CONCLUSION

The observed associations between AR (CAG)n and peripubertal fat accumulation and serum SHBG concentrations indicate that this genetic polymorphism may influence the androgen-dependent fine-tuning of metabolic and reproductive factors at a young age.