Prolactin response to metoclopramide does not distinguish patients with hypogonadotrophic hypogonadism from delayed...

The prolactin response to metoclopramide (MCP) was studied in 23 sexually immature males, 14 with isolated hypogonadotrophic hypogonadism (IHH) and nine with constitutional delayed puberty. Six of the 14 IHH patients had not been treated prior to our study, whereas eight had received long term therapy with testosterone or hCG for variable periods ranging from 1 to 20 years. We also measured the prolactin response to chlorpromazine (CPZ) in the untreated IHH men. In these untreated subjects, we observed a greatly diminished prolactin response after CPZ by comparison to that measured following MCP administration (peak 15 ng/ml, areas 86 units vs peak 43 ng/ml, area 416 units, respectively) (P less than 0.01). Furthermore, prolactin levels following MCP were similar in untreated (peak 43 ng/ml, area 416 units) and treated (peak 55 ng/ml, area 545 units, NS) IHH males as well as in boys with constitutional delayed puberty (peak 50 ng/ml, area 532 units, NS). In addition, responses in the three groups of patients were about half (P less than 0.01) those measured in normal men (peak 81 ng/ml, area 845 units). These data indicate that, unlike CPZ, MCP is not useful in distinguishing patients with hypogonadotrophic hypogonadism from boys with constitutional delayed puberty.