A simple test for the hormonal assessment of early puberty in boys.

The initial hormonal changes in male puberty occur at nighttime, with episodic rises of LH and testosterone (T). Only much later do the daytime levels of these hormones rise. Nocturnal sampling is impractical for routine clinical assessment, so we have examined the relationship between peak nocturnal T levels and those produced in the same subject by a single intravenous injection of gonadotrophin releasing hormone (GnRH, 100 micrograms) in the morning. Nocturnal T profiles and daytime GnRH tests have been conducted in eight boys in early (delayed) puberty, three with pubertal gynaecomastia in later puberty, two normal men, and one man with gynaecomastia. Excellent agreement was obtained between peak nocturnal and post-GnRH T levels. The serum testosterone level 3 hours after 100 micrograms IV GnRH is a simple and useful hormonal marker of pituitary-Leydig cell activity during puberty.