Contributions of common genetic variants to constitutional delay of puberty and idiopathic hypogonadotropic hypogonadism

CONTEXT

Constitutional delay of puberty (CDP) is highly heritable, but the genetic basis for CDP is largely unknown. Idiopathic hypogonadotropic hypogonadism (IHH) can be caused by rare genetic variants, but in about half of cases, no rare-variant cause is found.

OBJECTIVE

To determine whether common genetic variants that influence pubertal timing contribute to CDP and IHH.

DESIGN

Case-control study.

PARTICIPANTS

80 individuals with CDP; 301 with normosmic IHH, and 348 with Kallmann syndrome; control genotyping data from unrelated studies.

MAIN OUTCOME MEASURES

Polygenic scores (PGS) based on genome-wide association studies for timing of male pubertal hallmarks and age at menarche (AAM).

RESULTS

The CDP cohort had higher PGS for male pubertal hallmarks and for AAM compared to controls (for male hallmarks, Cohen's d = 0.85, p = 1 × 10-16; for AAM, d = 0.67, p = 1 × 10-10). The normosmic IHH cohort also had higher PGS for male hallmarks compared to controls, but the difference was smaller (male hallmarks d = 0.20, p = 0.003; AAM d = 0.10, p = 0.055). No differences were seen for the KS cohort compared to controls (male hallmarks d = 0.04, p = 0.45; AAM d = -0.03, p = 0.86).

CONCLUSIONS

Common genetic variants that influence pubertal timing in the general population contribute strongly to the genetics of CDP, weakly to normosmic IHH, and potentially not at all to KS. These findings demonstrate that the common-variant genetics of CDP and normosmic IHH are largely but not entirely distinct.

Growth, puberty and testicular function in boys born small for gestational age with a nonspecific disorder of sex development

OBJECTIVE

Being born small for gestational age (SGA) is frequently associated with unexplained disorders of sex development (nonspecific DSD) in boys. Little is known about their future growth, puberty and testicular function. Our objective is to determine the long-term endocrine outcome of boys born SGA who have a nonspecific DSD.

DESIGN

Boys with a nonspecific DSD born SGA and appropriate for GA (AGA) were retrieved through the International Disorders of Sex Development registry and retrospective data collected, based on a spreadsheet containing 102 items.

PATIENTS AND MEASUREMENTS

In total, 179 boys were included, of which 115 were born SGA and 64 were born AGA. Their growth and pubertal development were compared. Serum LH, FSH, testosterone, AMH and inhibin B levels in infancy and puberty were analysed to assess testicular function.

RESULTS

At 2 years of age, 30% of SGA boys had incomplete or absent catch-up growth. Boys born SGA also had higher LH during minipuberty and lower testosterone in stimulation tests (p = 0.037 and 0.040, respectively), as compared to boys born AGA. No differences were observed in timing or course of puberty or end-pubertal hormone levels.

CONCLUSIONS

Almost one out of three SGA boys with a nonspecific DSD experiences insufficient catch-up growth. In addition, our data suggest dysfunction of infantile Leydig cells or altered regulation of the hypothalamic-pituitary-gonadal axis in SGA boys during childhood. Sex steroid production during puberty seems unaffected.

Testosterone Therapy and Its Monitoring in Adolescent Boys with Hypogonadism: Results of an International Survey from the I-DSD Registry

It is unclear whether testosterone replacement therapy (TRT) in adolescent boys, affected by a range of endocrine diseases that may be associated with hypogonadism, is particularly common. The aim of this study was to assess the contemporary practice of TRT in boys included in the I-DSD Registry. All participating centres in the I-DSD Registry that had boys between 10 and 18 years of age and with a condition that could be associated with hypogonadism were invited to provide further information in 2019. Information on 162 boys was collected from 15 centres that had a median (range) number of 6 boys per centre (1.35). Of these, 30 (19%) from 9 centres were receiving TRT and the median (range) age at the start was 12.6 years (10.8-16.2), with 6 boys (20%) starting at <12 years. Median (range) age of boys not on TRT was 11.7 years (10.7-17.7), and 69 out of 132 (52%) were <12 years. TRT had been initiated in 20 of 71 (28%) boys with a disorder of gonadal development, 3 of 14 (21%) with a disorder of androgen synthesis, and all 7 (100%) boys with hypogonadotropic hypogonadism. The remainder who did not have TRT included 15 boys with partial androgen insensitivity, 52 with non-specific XY DSD, and 3 with persistent Müllerian duct syndrome. Before starting TRT, liver function and blood count were checked in 19 (68%) and 18 boys (64%), respectively, a bone age assessment was performed in 23 (82%) and bone mineral density assessment in 12 boys (43%). This snapshot of contemporary practice reveals that TRT in boys included in the I-DSD Registry is not very common, whilst the variation in starting and monitoring therapy is quite marked. Standardisation of practice may lead to more effective assessment of treatment outcomes.

OR15-03 High Prevalence of Gene Variants in Boys of Prepubertal Age with Clinical Suspicion of Central Hypogonadism and Low AMH

Introduction: In boys of prepubertal age, the diagnosis of central hypogonadism may be difficult to ascertain since gonadotropins and testosterone are normally low. Sertoli cell markers, like AMH and inhibin B, may be useful. In recent years, with the development of next generation sequencing (NGS) technology, the number of genes associated with central hypogonadism has had an exponential increase. However, even with these advanced techniques, the gene variants with potential pathogenicity can be found at present in only 30-50% of the patients. Hypothesis of the study: Low serum AMH is an appropriate screening biomarker to select patients for NGS, in order to make a genetic diagnosis in boys of prepubertal age with suspected central hypogonadism. Patients and methods: All patients aged 1-10 yr referred between 2001 and 2018 with clinical suspicion of central hypogonadism (micropenis and cryptorchidism and/or microorchidism), with low serum AMH (<10^th centile) were included. Serum AMH was determined by ELISA (Beckman-Coulter), and LH, FSH and testosterone (T) by ECLIA (Roche). NGS was performed with the TruSight™ One Sequencing Panel in a NextSeq® 500 sequencer (Illumina). Results are expressed as medians (range). Results: 13 patients were included. Age at first visit was 4.4 (0.1-9.2) yr. Cryptorchidism was present in all of them, micropenis in 10 and microorchidism in 11. Orchiopexy was required in 11 boys and the other 2 responded to hCG treatment. 4 patients had olfactory disturbances, 1 had sensory deafness and 1 had piebaldism. 2 patients had a family history of olfactory disturbances and/or central hypogonadism. 7 patients could be followed up to pubertal age, and the diagnosis of central hypogonadism was clinically confirmed. At age 6.1 yr (1.2-10), AMH was 159 pmol/L (65-363), LH was <0.1 IU/L in all, FSH was 0.61 IU/L (<0.1-1.9). 17 variants in 9 genes associated with central hypogonadism were found in 10 of 13 patients. 5 boys had 1 gene variant, while 4 had 2 gene variants and 1 had 3 gene variants indicating probable oligogenicity, in the following genes: FGFR1 (n:4), CHD7 (n:3), PROKR2 (n:2), SOX10 (n:2), AXL (n:2), HS6ST1 (n:1), AMHR2 (n:1), NSMF (n:1), DCC (n:1). Conclusion: A high prevalence of gene variants was found in boys of prepubertal age with a suspicion of central hypogonadism based on micropenis and cryptorchidism and/or microorchidism with low serum AMH.