weeks of normal embryonic development, the GnRH releasing neurons migrate from their original source in the nasal region and end up inside the hypothalamus. These neurons originate in an area of the developing head, the olfactory placode, that will give rise to the olfactory epithelium; they then pass through the cribriform plate, along with the fibres of the olfactory nerves, and into the rostral forebrain. From there they migrate to what will become the hypothalamus. Any problems with the development of the olfactory nerve fibres will prevent the progression of the GnRH releasing neurons towards the brain. Diagnosis Diagnosing KS and other forms of CHH is complicated by the difficulties in distinguishing between a normal constitutional delay of puberty or a case of KS/CHH. The diagnosis is often one of exclusion found during the workup of delayed puberty. In males, the use of age appropriate levels of testosterone can help to distinguish between a case of KS/CHH from a case of delayed puberty. If no puberty is apparent, especially no testicular development, then a review by a reproductive endocrinologist may be appropriate. If puberty is not apparent by the age of 16 then the person should be referred for endocrinological review. Post natal diagnosis of KS/CHH before the age of 6 months is sometimes possible as the normal post natal hormonal surge of gonadotropins along with testosterone or oestrogen is absent in babies with KS/CHH. This lack of detectable hormones in the blood can be used as a diagnostic indicator, especially in male infants. In females, diagnosis is sometimes further delayed as other causes of amenorrhoea normally have to be investigated first before a case of KS/CHH is considered. Diagnosis of KS/CHH normal involves a range of clinical, biochemical and radiological tests to exclude other conditions that can cause similar symptoms. Clinical tests Comparing height to standard growth charts. Determining the Tanner stage of sexual development. (Males with KS/CHH are normally at stage I or II with genitalia, females at stage I with breast development and both males and females at stage III with pubic hair development). Checking for micropenis and undescended testes (cryptorchidism) in males. Measuring testicular volume. Checking for breast development and age at menarche in females. Checking sense of smell using odorant panel or University of Pennsylvania Smell Identification Test (UPSIT) Checking for hearing impairment. Checking for missing teeth or presence of cleft lip and/or cleft palate.