Prior to puberty, Leydig cell function is assessed by measuring the response of plasma testosterone to gonadotrophin administration after three to five days of treatment with 1,000ΓÇô2,000iu/d of human chorionic gonadotrophin (hCG); in prepubertal boys, plasma testosterone should increase to some 7nmol/l (200ng/dl).
The response increases with the initiation of puberty and peaks in early puberty. In certain circumstances, the response of plasma LH to GnRH administration is utilised to assess the functional integrity of the hypothalamic-pituitary-Leydig cell axis. In general, the peak LH that follows a single GnRH injection correlates with the basal levels. A subnormal response indicates that an abnormality exists, but does not identify the site.
