UKMLA PLAB AMC USMLE Prometric MCQ

Correct Answer: B

Explanation:
The basic defect leading to hypogonadism in Kallmann's syndrome is an abnormality of hypothalamic GnRH secretion secondary to failure of gonadotropin-releasing hormone(GnRH)-producing neurons to migrate from the olfactory placode to the brain, and to agenesis of the olfactory bulbs. There is therefore a hypothalamic lack of the releasing hormone for gonadotrophins (GnRH). Patients with Kallmann's syndrome usually come to medical attention because of a delayed puberty or incomplete sexual development. Anosmia or hyposmia is present in 80% of the patients and establishes the diagnosis of the syndrome in individuals with isolated gonadotropin deficiency. Prepuberal testes, micropenis and cryptorquidism are usually seen. In women pubic and axillary hair are less reliable compared with absence of appearance of breast buds since adrenarche can occur independently of gonodarche. Other manifestations include: skeletal abnormalities (syndactily, short forth metacarpals, craniofacial asymmetry), mid-line defects (cleft-lip or -palate, color blindness, renal agenesis, nerve deafness), malrotation of the gut, congenital heart disease and neurologic findings (synkinesia, impaired 'smooth pursuit' eye movements and cerebellar dysfunction). X-linked disorder can be associated with X-linked ichthyosis, mental retardation, chondrodysplasia punctata, and short stature. Hypogonadotropic hypogonadism is established in adults by the finding of normal or low serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels in the presence of low concentrations of testosterone in males and estradiol in females.