Fig. 2. Spectrum of GnRH-induced LH secretion in men with GnRH deficiency. LH pulsations are indicated by asterisks. A, Normal adult male pattern of GnRH secretion with high amplitude regular LH pulsations and normal serum testosterone (T), testicular volume (TV) and sperm count; B, Disordered amplitude pattern of GnRH secretion in an CHH male, characterized by low amplitude LH pulsations, low serum T, and azoospermia; C, Sleep-entrained or developmental arrest pattern of LH secretion in an CHH male characterized by relatively low amplitude LH pulsations clustered during the night-time hours analogous to the pattern which normally occurs at puberty. Note that the TV is higher than in the subject with the apulsatile pattern; D, Apulsatile pattern of GnRH secretion in an CHH male with complete absence of endogenous LH pulsations, low serum T, prepubertal TV and azoospermia.