Kallmann syndrome occurs due to the absence of which hormone?

Kallmann syndrome is characterized by the failure of the hypothalamus to produce gonadotropin-releasing hormone (GnRH). This condition leads to hypogonadism, which is marked by delayed or absent sexual development due to inadequate stimulation of the pituitary gland to release gonadotropins such as luteinizing hormone (LH) and follicle-stimulating hormone (FSH). The absence of GnRH means that these key hormones cannot be produced in response to the body's needs, resulting in decreased levels of sex hormones such as testosterone in males or estrogen in females.

The dysfunction in GnRH production can also lead to other systemic issues, including anosmia (loss of the sense of smell), which is a common feature associated with Kallmann syndrome. Therefore, the underlying reason for the symptoms and hormonal deficiencies observed in patients with Kallmann syndrome directly relates to the absence of GnRH.