Metoclopramide test in the diagnosis of isolated hypogonadotrophic hypogonadism

The responses of serum prolactin (Prl) to metoclopramide and LH and FSH to GnRH were studied simultaneously in 9 boys with hypogonadotrophic hypogonadism (HH), 7 boys with constitutional delay of puberty (D) and 15 controls. Metoclopramide increased the Prl levels in all groups. The boys with HH had lower Prl responses than the controls, whereas the boys with D had similar responses to the controls. Of the 9 boys with HH, 8 had subnormal Prl responses, 3 subnormal LH and none subnormal FSH. A metoclopramide test is clearly more sensitive than a GnRH test in differentiating HH and D and appears to make the differentiation between these two conditions clearer.