Male patients with hypogonadotropic hypogonadism due to isolated luteinizing hormone (LH) deficiency have normal sexual differentiation but fail to develop spontaneous puberty. Absence of LH alters Leydig cell proliferation and maturation and impairs the onset of normal spermatogenesis, which requires high levels of intratesticular testosterone. Infertility and very low levels of spermatogenesis generally persist in affected men despite long-term exposure to gonadotropin therapy. Female patients exhibit normal pubertal development and menarche, followed by oligomenorrhea and anovulatory secondary amenorrhea (summary by Basciani et al., 2012). Congenital idiopathic hypogonadotropic hypogonadism (IHH) is a disorder characterized by absent or incomplete sexual maturation by the age of 18 years, in conjunction with low levels of circulating gonadotropins and testosterone and no other abnormalities of the hypothalamic-pituitary axis. Idiopathic hypogonadotropic hypogonadism can be caused by an isolated defect in gonadotropin-releasing hormone (GNRH; 152760) release, action, or both. Other associated nonreproductive phenotypes, such as anosmia, cleft palate, and sensorineural hearing loss, occur with variable frequency. In the presence of anosmia, idiopathic hypogonadotropic hypogonadism has been called 'Kallmann syndrome (KS),' whereas in the presence of a normal sense of smell, it has been termed 'normosmic idiopathic hypogonadotropic hypogonadism (nIHH)' (summary by Raivio et al., 2007). Because families have been found to segregate both KS and nIHH, the disorder is here referred to as 'hypogonadotropic hypogonadism with or without anosmia (HH).' For a general phenotypic description and discussion of genetic heterogeneity of hypogonadotropic hypogonadism, see 147950. Reviews Arnhold et al. (2009) noted that the clinical manifestations of female patients with hypogonadotropic hypogonadism due to mutations in LHB are very similar to those of women with hypergonadotropic hypogonadism due to inactivating mutations of the LH receptor (see 238320): all have female external genitalia, spontaneous development of normal pubic hair and breasts at puberty, and normal to late menarche followed by oligoamenorrhea and infertility. Pelvic ultrasound shows a small or normal uterus and normal or enlarged ovaries with cysts. However, women with LHB mutations can be treated with luteinizing hormone or chorionic gonadotropin (CG; 118860) replacement therapy; women with LH receptor mutations are resistant to LH, and no treatment is effective in recovering their fertility.

PROP1-related combined pituitary hormone deficiency (CPHD) is associated with deficiencies of: growth hormone (GH); thyroid-stimulating hormone (TSH); the two gonadotropins, luteinizing hormone (LH) and follicle-stimulating hormone (FSH); prolactin (PrL); and occasionally adrenocorticotropic hormone (ACTH). At birth, in contrast to individuals with congenital CPHD of other etiologies, neonates with PROP1-related CPHD lack perinatal signs of hypopituitarism. Mean birth weights and lengths are usually within the normal range and neonatal hypoglycemia and prolonged neonatal jaundice are not prevalent findings. Most affected individuals are ascertained because of short stature during childhood. Although TSH deficiency can present shortly after birth, TSH deficiency usually occurs with or after the onset of GH deficiency. Hypothyroidism is usually mild. FSH and LH deficiencies are typically identified at the age of onset of puberty. Affected individuals can have absent or delayed and incomplete secondary sexual development with infertility. Untreated males usually have a small penis and small testes. Some females experience menarche but subsequently require hormone replacement therapy. ACTH deficiency is less common and, when present, usually occurs in adolescence or adulthood. Neuroimaging of hypothalamic-pituitary region usually demonstrates a hypoplastic or normal anterior pituitary lobe and a normal posterior pituitary lobe.

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.

Familial adrenal hypoplasia with absent pituitary luteinizing hormone is a rare endocrine disease characterized by a miniature adult type of congenital adrenal hypoplasia (residual adrenal cortex is composed of a small amount of permanent adult cortex with normal structural organization), selective absence of pituitary luteinizing hormone in otherwise normal brain, and neonatal demise. Patients present with hypogonadotropic hypogonadism, hypoglycemia, seizures, encephalopathy and diabetes insipidus. There have been no further descriptions in the literature since 1988.

Self-limited delayed puberty (DPSL) is characterized by delayed development of Tanner stage G2 accompanied by low serum gonadotropins. Affected individuals experience spontaneous attainment of Tanner stage G4 by 18 years of age, with normalization of gonadotropins, which excludes a diagnosis of hypogonadotropic hypogonadism (see 147950) (Mancini et al., 2020).

Any combined pituitary hormone deficiencies, genetic form in which the cause of the disease is a mutation in the OTX2 gene.

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.

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.

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.

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.

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.

Hypogonadotropic hypogonadism-27 without anosmia (HH27) is characterized by lack of pubertal development associated with onset of obesity in early adolescence (Topaloglu et al., 2022). Congenital idiopathic hypogonadotropic hypogonadism (IHH) is a disorder characterized by absent or incomplete sexual maturation by the age of 18 years, in conjunction with low levels of circulating gonadotropins and testosterone and no other abnormalities of the hypothalamic-pituitary axis. Idiopathic hypogonadotropic hypogonadism can be caused by an isolated defect in gonadotropin-releasing hormone (GNRH; 152760) release, action, or both. Other associated nonreproductive phenotypes, such as anosmia, cleft palate, and sensorineural hearing loss, occur with variable frequency. In the presence of anosmia, idiopathic hypogonadotropic hypogonadism has been called 'Kallmann syndrome (KS),' whereas in the presence of a normal sense of smell, it has been termed 'normosmic idiopathic hypogonadotropic hypogonadism (nIHH)' (summary by Raivio et al., 2007). Because families have been found to segregate both KS and nIHH, the disorder is here referred to as 'hypogonadotropic hypogonadism with or without anosmia (HH).'

Cerebellar dysfunction, impaired intellectual development, and hypogonadotropic hypogonadism (CDIDHH) is characterized by delayed motor development, ataxia, severe progressive scoliosis, moderate to severe intellectual disability, and delayed sexual development. Cerebellar hypoplasia has been observed in some patients (Whittaker et al., 2021).

Combined pituitary hormone deficiency-8 (CPHD8) is an autosomal dominant disorder characterized by deficiency of one or more of the pituitary hormones. Affected individuals have short stature due to growth hormone (GH; 139250) deficiency with variable deficiencies of other pituitary hormones, including TSH (see 188540), ACTH, and LH/FSH (see 118850). Posterior pituitary deficiency leading to central diabetes insipidus is rare (Bashamboo et al., 2017). Many patients are diagnosed with 'pituitary stalk interruption syndrome' (PSIS), which is characterized by a thin or absent pituitary stalk, absent or ectopic posterior pituitary, and hypoplasia of the anterior pituitary demonstrated on brain imaging, although this classic triad may be incomplete. Brauner et al. (2020) noted the complex phenotypic and genetic heterogeneity of PSIS, and concluded that it is a feature of genetic disorders or syndromes rather than a specific clinical entity. For a discussion of genetic heterogeneity of combined pituitary hormone deficiency, see CPHD1 (613038).