The effect of changing gonadotropin-releasing hormone pulse frequency on puberty.
Bridges NA., Hindmarsh PC., Matthews DR., Brook CG.
We have examined the effect of using different pulse frequencies of exogenous GnRH to induce puberty and the time relationship among LH, FSH, sex steroids, and GH in these individuals. Five girls and three boys with delayed puberty received exogenous GnRH at either 3-h frequency (slow) or every 45 min (fast). Treatment was initially given overnight and increased to 24 h when breast stage 3 in girls or testicular volume of 10 mL in boys was attained. Twenty-four-hour gonadotropin profiles were performed after 5 days, 1 month, 3 months, 6 months, and 1 yr of treatment. Temporal relationships among LH, FSH, and estradiol; LH and testosterone; GH and estradiol; and GH and testosterone were examined by cross-correlation. There was no difference in the rate of pubertal progress between the groups. Mean serum gonadotropin and sex steroid levels did not differ. LH was correlated with estradiol for both groups at 240 min (slow group, r = 0.54; fast group, r = 0.50). Estradiol correlated with LH at 300 min in the slow group (r = -0.41) and 200 min in the fast group (r = -0.37). FSH correlated with estradiol at 140 min in the slow group (r = 0.62) and 160 min in the fast group (r = 0.50). A rise in estradiol occurred 140-160 min after a rise in FSH and 240 min after a rise in LH. A rise in estradiol was followed 200-300 min later by a fall in LH. LH was correlated with testosterone at 60 min in the slow group (r = 0.73) and at 40 min in the fast group (r = 0.55). Testosterone correlated with LH at 420 min in the slow (r = -0.67) and 460 min in the fast group (r = -0.40). A rise in LH was followed 40-60 min later by a rise in testosterone. A rise in testosterone was followed by fall in LH 420-460 min later. GH correlated with estradiol at 320 min in the slow group (r = 0.37) and 380 min in the fast group (r = 0.38). A rise in GH was followed, after 320-380 min, by a rise in estradiol. There was a correlation between GH and testosterone in the slow group after 280 min (r = 0.44). A rise in GH was followed by a rise in testosterone after 280 min. The pituitary-gonadal axis is sufficiently robust to allow puberty to progress with different fixed pulse frequencies. There is a temporal relationship among LH, FSH, and estradiol secretion and between LH and testosterone secretion. We have demonstrated the feedback effect of sex steroids at the level of the pituitary and the time course of the effect of GH on gonadal function.