Infants born with severe central disorders of the hypothalamic-pituitary-gonadal axis leading to gonadotropin deficiency not only lack pubertal development in adolescence, but also lack infantile mini-puberty. This period of mini-puberty, where infants have gonadotropin and sex steroid concentrations up into the adult range, is vital for future reproductive capacity, particularly in boys. At present, there is no consensus on the diagnosis or management of infants with gonadotropin deficiency due to congenital hypogonadotropic hypogonadism or multiple pituitary hormone deficiency. Case series suggest that gonadotropin treatment in male infants with absent mini-puberty is effective in promoting both testicular descent in those with undescended testes and also facilitating increased penile size. Moreover, replacement with follicle-stimulating hormone increases the testicular Sertoli cell population, measurable as an increase in testicular volume and inhibin B, thus hypothetically increasing the capacity for spermatogenesis in adult life for these patients. However, long-term follow-up data is limited for both outcomes pertaining to fertility and nonreproductive sequelae, including neurodevelopment and psychological well-being. The use of international registries for patients with gonadotropin deficiency is a key element in the collection of high-quality, geographically widespread data to inform best-practice management from birth to adulthood.

This case report describes a man in his 20s presenting with bilateral crypto-orchidism, micropenis and underdeveloped secondary sexual characteristics. The patient also exhibited hyposmia, eunuchoid stature and gynecomastia. Biochemical investigations revealed low levels of testosterone, luteinising hormone and follicle-stimulating hormone. Hence, he was diagnosed with Kallmann syndrome. Imaging studies showed an absent right kidney and cystic dilatation of the distal ureteric bud, seminal vesicle and absent/hypoplastic ejaculatory duct. The association of hypogonadotropic hypogonadism with Zinner syndrome, a rare condition characterised by renal agenesis, seminal vesicle cyst and ejaculatory duct obstruction, was noted.

We reported a novel variant in Kallmann syndrome. It not only determines the clinical importance of whole exome sequencing for identification of genetic pathogenic variants, but also enriches the ANOS1 genetic spectrum of CHH patients in Chinese population.

UNASSIGNED: This study aimed to characterize the clinical phenotype and genetic variations in patients with Kallmann syndrome (KS).
UNASSIGNED: This study involved the collection and analysis of clinical data from an individual with sporadic KS. Following this, peripheral blood samples were obtained from the patient and his parents. Genomic deoxyribonucleic acid was extracted and subjected to whole-exome sequencing and genomic copy number variation (CNV) detection. Finally, Sanger sequencing was performed to validate the suspected pathogenic variants.
UNASSIGNED: Whole-exome sequencing confirmed that the child carried both the IL17RD variant (c.2101G>A, p.Gly701Ser) inherited from the mother and the new CPEB4 variant (c.1414C>T, p.Arg472*). No pathogenic CNVs were identified in CNV testing.
UNASSIGNED: Bioinformatics analysis shows that the IL17RD protein undergoing Gly701Ser mutation and is speculated to be phosphorylated and modified, thereby disrupting fibroblast growth factor signaling. This study also suggested that the CPEB4 might play a crucial role in the key signaling process affecting olfactory bulb morphogenesis. Overall, the findings of this study broaden the gene expression profile of KS-related pathogenic genes. This offers a new avenue for exploring the pathogenic mechanism of KS and provides valuable insights for precise clinical diagnosis and treatment strategies for this condition.

There is very little knowledge regarding the terminal nerve, from its implications in the involvement and pathogenesis of certain conditions, to its embryological origin. With this review, we try to summarize the most important evidence on the terminal nerve, aiming to clarify its anatomy and the various functions attributed to it, to better interpret its potential involvement in pathological processes. Recent studies have also suggested its potential role in the control of human reproductive functions and behaviors. It has been hypothesized that it plays a role in the unconscious perception of specific odors that influence autonomic and reproductive hormonal systems through the hypothalamic-pituitary-gonadal axis. We used the PubMed database and found different articles which were then selected independently by three authors. We found 166 articles, of which, after careful selection, only 21 were analyzed. The terminal nerve was always thought to be unimportant in our body. It was well studied in different types of animals, but few studies have been completed in humans. For this reason, its function remains unknown. Studies suggest a possible implication in olfaction due to the anatomical proximity with the olfactive nerve. Others suggest a more important role in reproduction and sexual behaviors. New emerging information suggests a possible role in Kallmann syndrome and COVID-19.

BACKGROUND: Hypogonadotropic hypogonadism (HH) is due to impaired gonadotropin releasing hormone (GnRH) action resulting in absent puberty and infertility. At least 44 genes have been identified to possess genetic variants in 40-50% of nHH/KS, and 2-20% have presumed digenic disease, but not all variants have been characterized in vitro.
OBJECTIVE: The prevalence of pathogenic (P)/likely pathogenic (LP) variants in monogenic and digenic nHH/KS is lower than reported.
METHODS: Cross-sectional study.
METHODS: University Research Laboratory.
METHODS: 158 patients with nHH/KS.
METHODS: Exome sequencing (ES) was performed and variants were filtered for 44 known genes using Varsome and confirmed by Sanger Sequencing.
METHODS: P/LP variants in nHH/KS genes.
RESULTS: ES resulted in >370,000 variants, from which variants in 44 genes were filtered. Thirty-one confirmed P/LP variants in 10 genes (ANOS1, CHD7, DUSP6, FGFR1, HS6ST1, KISS1, PROKR2, SEMA3A, SEMA3E, TACR3), sufficient to cause disease, were identified in 30/158 (19%) patients. Only 2/158 (1.2%) patients had digenic variant combinations: a male with hemizygous ANOS1 and heterozygous TACR3 variants and a male with heterozygous SEMA3A and SEMA3E variants. Two patients (1.2%) had compound heterozygous GNRHR (autosomal recessive) variants-one P and one variant of uncertain significance (VUS). Five patients (3.2%) had heterozygous P/LP variants in either GNRHR or TACR3 (both autosomal recessive), but no second variant.
CONCLUSIONS: Our prevalence of P/LP variants in nHH/KS was 19%, and digenicity was observed in 1.2%. These findings are less than those previously reported, and probably represent a more accurate estimation since VUS are not included.

OBJECTIVE: Hormone replacement therapy with testosterone for pubertal induction in boys with congenital hypogonadotropic hypogonadism (CHH) achieves virilization but not spermatogenesis. By contrast, human chorionic gonadotropin (hCG) and recombinant follicle stimulating hormone (rFSH) provides both virilization and spermatogenesis. Fertility outcomes of boys treated with recombinant therapy during adolescence have been infrequently described. We report fertility induction and pregnancy outcomes in CHH patients treated with recombinant gonadotropins during puberty.
METHODS: Data of six subjects with CHH (n = 3 Kallmann syndrome & n = 3 Isolated hypogonadotropic hypogonadism) treated with hCG and FSH for pubertal induction were reviewed. Of these, five underwent subsequent fertility induction while one desired fertility at the end of pubertal induction.
RESULTS: Partners of all subjects achieved pregnancies using hCG and rFSH, all with full term live births. All infants were clinically normal.
CONCLUSIONS: This study provides early evidence of proof of concept of use of gonadotropin induction of puberty being beneficial in subsequent fertility outcome.

Pubertal delay can be due to hypogonadotropic hypogonadism (HH), which may occur in association with anosmia or hyposmia and is known as Kallmann syndrome (OMIM #308700). Recently, hypogonadotropic hypogonadism has been suggested to overlap with Witteveen-Kolk syndrome (WITKOS, OMIM #613406) associated with 15q24 microdeletions encompassing SIN3A. Whether hypogonadotropic hypogonadism is due to haploinsufficiency of SIN3A or any of the other eight genes present in 15q24 is not known. We report the case of a female patient with delayed puberty associated with intellectual disability, behavior problems, dysmorphic facial features, and short stature, at the age of 14 years. Clinical, laboratory, and imaging assessments confirmed the diagnosis of Kallmann syndrome. Whole-exome sequencing identified a novel heterozygous frameshift variant, NM_001145358.2:c.3045_3046dup, NP_001138830.1:p.(Ile1016Argfs*6) in SIN3A, classified as pathogenic according to the American College of Medical Genetics and Genomics (ACMG/AMP) criteria. Reverse phenotyping led to the clinical diagnosis of WITKOS. No other variant was found in the 96 genes potentially related to hypogonadotropic hypogonadism. The analysis of the other contiguous seven genes to SIN3A in 15q24 did not reveal any clinically relevant variant. In conclusion, these findings point to SIN3A as the gene in 15q24 related to the reproductive phenotype in patients with overlapping WITKOS and Kallmann syndrome.

During embryonic development, the olfactory placode (OP) generates migratory neurons, including olfactory pioneer neurons, cells of the terminal nerve (TN), gonadotropin-releasing hormone-1 (GnRH-1) neurons, and other uncharacterized neurons. Pioneer neurons from the OP induce olfactory bulb (OB) morphogenesis. In mice, GnRH-1 neurons appear in the olfactory system around mid-gestation and migrate via the TN axons to different brain regions. The GnRH-1 neurons are crucial in controlling the hypothalamic-pituitary-gonadal axis. Kallmann syndrome is characterized by impaired olfactory system development, defective OBs, secretion of GnRH-1, and infertility. The precise mechanistic link between the olfactory system and GnRH-1 development remains unclear. Studies in humans and mice highlight the importance of the prokineticin-2/prokineticin-receptor-2 (Prokr2) signaling pathway in OB morphogenesis and GnRH-1 neuronal migration. Prokr2 loss-of-function mutations can cause Kallmann syndrome (KS), and hence the Prokr2 signaling pathway represents a unique model to decipher the olfactory/GnRH-1 connection. We discovered that Prokr2 is expressed in the TN neurons during the critical period of GnRH-1 neuron formation, migration, and induction of OB morphogenesis. Single-cell RNA sequencing identified that the TN is formed by neurons distinct from the olfactory neurons. The TN neurons express multiple genes associated with KS. Our study suggests that the aberrant development of pioneer/TN neurons might cause the KS spectrum.

BACKGROUND: 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.
METHODS: Case-control study.
METHODS: 80 individuals with CDP; 301 with normosmic IHH, and 348 with Kallmann syndrome; control genotyping data from unrelated studies.
METHODS: 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.