Low or normal FSH and LH levels along with low testosterone and estradiol levels in children with short stature and delayed pubertal development may indicate Constitutional delay Secondary hypogonadism (hypogonadotropic hypogonadism) Functional hypogonadotropic hypogonadism (caused by hypothyroidism, inflammatory conditions, undernutrition, or excessive exercise) FSH measurement is particularly important for the diagnosis of primary hypogonadism because FSH has a longer half life, is more sensitive, and shows less variability than LH.