Kallmann's syndrome is a form of idiopathic hypogonadotropic hypogonadism (IHH) associated with hyposmia or anosmia. The syndrome may be familial, and men are more commonly affected than women. Kallmann's syndrome and IHH with normal olfaction are similar in clinical presentation and treatment. In both cases, the major abnormality appears to be deficiency of hypothalamic GnRH secretion. Patients with Kallmann's syndrome usually come to medical attention because of abnormal pubertal development. Affected individuals can have associated abnormalities that include cryptorchidism, gynecomastia, cleft lip or palate, and various less common features. The evaluation should include a search for secondary causes of gonadotropin deficiency, evidence of other pituitary hormone deficiencies, and an imaging study to exclude anatomic lesions of the hypothalamus or pituitary. In younger patients, differentiating IHH from constitutional delay of puberty can be very difficult, and can be done conclusively only through prolonged "follow-up" observation. Gonadal steroid replacement is the preferred treatment for inducing and maintaining secondary sexual development until fertility is desired. Fertility can be achieved in many affected individuals with HCG and HMG or with pulsatile GnRH administration.
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