Developmental changes in neuroendocrine regulation of gonadotropin secretion in gonadal dysgenesis

Patients with gonadal dysgenesis have a marked increase in gonadotropin levels at the age when puberty normally occurs. To determine whether this increase results from a change in the frequency or the amplitude of gonadotropin pulses, we measured the 24-h profile of plasma LH and FSH by RIA in 31 patients with gonadal dysgenesis, aged 2-20 yr. Gonadotropin pulses were defined as a rise from nadir to peak that exceeded 3 times the intraassay coefficient of variation. This criterion, based on an empirical study of RIA noise, reduced the rate of false positive peaks to less than 3-4/24 h. Using this criterion, peak amplitude increased significantly at the time of puberty for both LH and FSH (P less than 0.01). The overall frequency of gonadotropin pulses (the sum of the FSH peaks plus the LH peaks that occurred without a concomitant FSH peak), however, did not differ among prepubertal (12.7 +/- 1.8 peaks/24 h), pubertal aged (14.3 +/- 2.3 peaks/24 h), and adult patients (14.7 +/- 0.9 peaks/24 h). Thus, the increase in gonadotropin concentration in pubertal aged patients with gonadal dysgenesis appears to result primarily from an increase in gonadotropin peak amplitude rather than an increase in peak frequency.