The packet lists ANOS1 as the gene associated with this condition, located on the X chromosome, and the ClinGen validity is definitive. The inheritance pattern in the packet is X-linked, consistent with the definition of the X-linked form of Kallmann syndrome. According to the GeneReviews chapter, genotype and phenotype correlations are limited: no reproductive or non-reproductive phenotype is specific to a single pathogenic variant or a particular type of variant in IGD-related genes. The chapter also states that the Kallmann syndrome phenotype, meaning both IGD and anosmia, is generally completely penetrant in males with an ANOS1 pathogenic variant, whereas other non-reproductive phenotypes may show variable penetrance even with the same ANOS1 defect. No molecular mechanism field is certified in the packet.

The packet does not include a dedicated diagnostic methods field, and the following draws on the GeneReviews chapter for isolated GnRH deficiency. The chapter describes IGD as suspected in the setting of absent or partial puberty in adolescents with low serum testosterone or estradiol, and incomplete sexual maturation on physical examination assessed by Tanner staging. Males are described as typically having Tanner stage I-II genitalia with prepubertal testicular volumes, and females as typically having Tanner stage I breast development and amenorrhea, with some exceptions. Laboratory findings described include low sex steroid levels with inappropriately low or normal luteinizing hormone and follicle stimulating hormone, while other anterior pituitary hormones are typically normal. Imaging is described as typically showing a normal-appearing hypothalamus and pituitary, whereas Kallmann syndrome is typically associated with aplasia or hypoplasia of the olfactory bulbs, sulci, or tracts. Olfactory function is described as evaluated by history and by formal smell tests such as the University of Pennsylvania smell identification test; individuals with self-reported complete anosmia, or hyposmia or anosmia on that test, are described as diagnosed with Kallmann syndrome, and those with normal olfaction as having normosmic IGD. The chapter states that the diagnosis is established on clinical and biochemical investigations, and that a genetic diagnosis can be made when pathogenic or likely pathogenic variants are identified. The chapter also lists acquired causes of low gonadotropin secretion as part of the differential diagnosis.

No approved treatments or orphan-drug records are listed in the packet, so no approval claims are made here. According to the GeneReviews chapter on IGD, management after diagnosis is described as including assessment of clinical manifestations of hypogonadism, laboratory assessment of luteinizing hormone, follicle stimulating hormone, and sex steroids, evaluation for possible non-reproductive features such as renal, hearing, skeletal, dental, and eye findings and developmental status, attention to bone health, and involvement of a clinical geneticist or genetic counselor. The chapter cites an expert European consensus statement on IGD management.

For males aged 18 years and older, the chapter describes treatment options as sex steroids, gonadotropins, and pulsatile GnRH administration, with the choice determined by the goal of treatment, either to induce and maintain secondary sex characteristics or to induce and maintain fertility, and by individual preference. When fertility is not immediately desired, testosterone replacement is described as the most practical option, delivered by injectable or transdermal routes, and usually required indefinitely once puberty is initiated. The chapter also describes reversal of IGD in about 10% of males, in which endogenous activity of the hypothalamic-pituitary axis is evident.

Surveillance described in the chapter includes regular assessment of sexual maturation, hormone concentrations, and bone age in children with suggestive findings from age 11 years onward, and measurement of serum sex steroid levels and bone mineral density at regular intervals in individuals with a confirmed diagnosis. Dosing and schedules are not summarized here.

A dedicated natural history field is not certified in the packet. According to the GeneReviews chapter on IGD, the clinical course depends on the developmental stage at which the deficiency first occurred, and a definitive diagnosis is typically made around age 18 years. The chapter notes that reversal of IGD, defined as restoration of normal serum testosterone after cessation of even brief hormonal treatment, occurs in about 10% of men with IGD, including those with Kallmann syndrome, and that its physiologic basis is not fully understood. Survival and life expectancy figures are not supplied.

Certified active clinical trial records are present, and several are listed with trial details. Examples include NCT01500447 (recruiting), titled 'Inherited Reproductive Disorders'; NCT01601171 (recruiting), titled 'Genetics of Reproductive Disorders (Including Kallmann Syndrome) and Cleft Lip and/or Palate'; and NCT04463316 (recruiting), titled 'GROWing Up With Rare GENEtic Syndromes'. Active clinical trials for this condition are listed on ClinicalTrials.gov.