Inherited Reproductive Disorders

* INCLUSION CRITERIA: The essential inclusion criteria include: 1. failure to go through a normal, age-appropriate, spontaneous puberty and low sex steroid levels in the setting of low/normal gonadotropins (due to substantial variability among patient presentations, this will be based on the clinical judgement of the Investigator), or 2. abnormally early development of puberty, or 3. normal puberty with subsequent development of low gonadotropin levels, or 4. individuals with features indicating an increased risk of hypogonadotropic hypogonadism. 5. Family members: both affected and unaffected family members are strongly encouraged to participate. EXCLUSION CRITERIA: Since hypogonadotropic hypogonadism is a rare condition, this protocol remains open to enrollment so that we may study all subjects that are both qualified and interested in participating. Because HH represents a spectrum, where associated clinical findings may provide phenotypic clues to the assessment of inheritability and underlying physiology, exclusion criteria are very limited: * Patients who have additional pituitary deficiencies, effectively ruling out isolated GnRH deficiency, whether these deficiencies are congenital or acquired (e.g. secondary to malignancy, infection, or irradiation). * Patients who are taking medications known to affect GnRH secretion, such as corticosteroids or continuous opiate administration (or were taking them at the time of diagnosis).