A 15-year-old boy has no testicular enlargement (testicular volume 2 mL) and no axillary or pubic hair. His height velocity is 3 cm/year. Bone age is 11 years. Baseline LH/FSH are undetectable; after GnRH stimulation, LH rises minimally. Smell is reported as absent. The most likely diagnosis is:

• A Kallmann syndrome ✓
• B Constitutional delay of growth and puberty (CDGP)
• C Klinefelter syndrome
• D Primary hypogonadism (anorchia)

Explanation

Kallmann syndrome is a form of isolated hypogonadotropic hypogonadism caused by failure of GnRH neuron migration from the olfactory placode to the hypothalamus, pathognomically accompanied by anosmia or hyposmia. It presents with delayed puberty, low/absent LH/FSH, poor GnRH stimulation response, and absent smell. Bone age is delayed. CDGP is the most common cause of delayed puberty but features normal smell and eventual spontaneous pubertal progression. Klinefelter syndrome (47,XXY) shows elevated FSH/LH (primary hypogonadism). Anorchia would show elevated FSH/LH.

Reference: Ghai Essential Pediatrics, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.