Primary gonadotropin deficiency is associated with very low levels of FSH and LH, concordant bone age, normal stature -  unless multiple pituitary deficiencies including GH are associated -  and normal karyotype. Response to LHRH testing and study of LH pulsatility are useful for diagnosis. Radiographic imaging of the hypothalamic-pituitary regions shows normal findings while baseline and reserve testing of the other hypothalamic-pituitary axes are needed to detect possible multiple pituitary deficiencies. Associated features may sometimes suggest an etiology, for example in cases of familial history of consanguinity or similar cases. Different genes have already been identified and a molecular diagnosis is sometimes possible.

Syndromic Primary Gonadotropin Deficiency
Multiple Endocrine Deficiencies
Idiopathic dwarfism is associated with delayed puberty. After confirmation of the GH deficiency, treatment with recombinant GH will try to induce pubertal development, which needs IGF-1. IGF-1 enhances ovarian stimulation by LH and FSH. Moreover, multiple pituitary deficiencies, including thyreotroph, corticotroph and gonadotroph, are possible in cases of a mutation of recently identified developmental genes, such as PROP-1.

Obesity

• Prader-Willi syndrome is characterized by massive obesity, infantile hypotonia, mental retardation, short stature, small hands and feet, and characteristic facies. Delayed puberty is of hypothalamic origin and sometimes improves following weight reduction. A deletion of the long arm of chromosome 15 may be found in some patients.
• Laurence-Moon-Bield syndrome associates obesity, polydactyly, mental retardation and retinitis pigmentosa with delayed puberty. The mode of inheritance is autosomal recessive.
• Mutation of the leptin Ob or Ob-R gene is exceptional. Clinical features include morbid obesity with impaired food behavior, decreased basal metabolic rate and IHH. Puberty may be induced by recombinant leptin in cases of mutated Ob gene.
• Mutations of the human prohormone convertase 1 (PC1) gene have been reported with obesity, IHH, hypocortisolism, and abnormal glucose homeostasis due to very low insulin level and high proinsulin level.

Anosmia: The Kallmann Syndrome (KS)
Association of anosmia with IHH (idiopathic IHH) is called the KS. In boys, it may be due to the mutated X-linked Kal gene. This gene encodes a protein, anosmin, which plays a role in the migration of LHRH neurons and olfactory nerves to the hypothalamus. In fact, in KS only 14% of familial and 11% of sporadic male cases are associated with mutation of the Kal gene. The majority, including female cases of KS, are caused by defects on at least two autosomal genes that are currently unknown with either a dominant or recessive mode of inheritance.