Gonadotropin-releasing hormone infusion test in the distinction of hypopituitary patients from normal subjects.

We undertook a pilot study to determine whether infusion of gonadotropin-releasing hormone (GnRH) might improve the distinction of hypogonadotropinism from the normal state and might permit gonadotropin deficiency to be diagnosed in the prepubertal child. Normal prepubertal and pubertal boys had a greater luteinizing hormone (LH) reaction (delta LH 54 +/- 15 [SD] ng/ml and 165 +/- 23 ng/ml, respectively) to a 4-hour infusion (100 microgram/hour) than to a 100-microgram bolus of GnRH (19 +/- 9 and 52 +/- 35 ng/ml). These augmented responses were observed in boys with delayed puberty, but not in apparently hypogonadotropic males greater than or equal to 12 years old. LH (delta LH 445 to 1602 ng/ml) and FSH (delta FSH 718 to 2112 ng/ml) surges were induced consistently by GnRH infusion only in normal, postmenarchial females. In all, of 13 hypopituitary cases classified as hypogonadotropic on the basis of a subnormal response to GnRH infusion, 31% had a normal response to the GnRH bolus (P = 0.05). Thus, GnRH infusion testing seems to improve the distinction of hypogonadotropic patients from normal individuals, including boys with delayed puberty.