A genetically heterogeneous disorder caused by hypothalamic GNRH deficiency and OLFACTORY NERVE defects. It is characterized by congenital HYPOGONADOTROPIC HYPOGONADISM and ANOSMIA, possibly with additional midline defects. It can be transmitted as an X-linked (GENETIC DISEASES, X-LINKED), an autosomal dominant, or an autosomal recessive trait.

Isolated gonadotropin-releasing hormone (GnRH) deficiency (IGD) is characterized by inappropriately low serum concentrations of the gonadotropins LH (luteinizing hormone) and FSH (follicle-stimulating hormone) in the presence of low circulating concentrations of sex steroids. IGD is associated with a normal sense of smell (normosmic IGD) in approximately 40% of affected individuals and an impaired sense of smell (Kallmann syndrome) in approximately 60%. IGD can first become apparent in infancy, adolescence, or adulthood. Infant boys with congenital IGD often have micropenis and cryptorchidism. Adolescents and adults with IGD have clinical evidence of hypogonadism and incomplete sexual maturation on physical examination. Adult males with IGD tend to have prepubertal testicular volume (i.e., <4 mL), absence of secondary sexual features (e.g., facial and axillary hair growth, deepening of the voice), decreased muscle mass, diminished libido, erectile dysfunction, and infertility. Adult females have little or no breast development and primary amenorrhea. Although skeletal maturation is delayed, the rate of linear growth is usually normal except for the absence of a distinct pubertal growth spurt.

(kallmann's syndrome) Anosmia due to failure of the olfactory lobes to develop, with secondary hypogonadism due to gonadotropic hormone deficiency.

(hypogonadotropic hypogonadism with anosmia) An X-linked or autosomal dominant genetic syndrome characterized by hypogonadotropic hypogonadism and anosmia.

(hypogonadotropic hypogonadism with anosmia) An X-linked or autosomal dominant syndrome due to mutation(s) in a number of genes, including FGFR1 (encoding fibroblast growth factor receptor 1), KAL1 (encoding anosmin-1), PROKR2 (encoding prokineticin receptor-2), CDH7 (encoding chromodomain helicase DNA binding protein 7), and FGF8 (encoding fibroblast growth factor 8). This condition is characterized by an impaired sense of smell and a deficiency of gonadotropin-releasing hormone, resulting in hypogonadotropic hypogonadism. Additional features may include cleft lip or palate, unilateral kidney dysgenesis, and synkinesia.

Kallmann syndrome (KS) is a condition that causes hypogonadotropic hypogonadism (HH) and an impaired sense of smell. HH affects the production of the hormones needed for sexual development. It is present from birth and is due to deficiency of gonadotropin-releasing hormone (GnRH). KS is often diagnosed at puberty due to lack of sexual...