THE EFFECT OF LUTEINIZING-HORMONE-RELEASING HORMONE ANALOG FOR CENTRAL PRECOCIOUS PUBERTY ON GROWTH-HORMONE (GH) AND GH-BINDING PROTEIN

The pubertal growth spurt is characterized by a marked increase in the amplitude of GH secretory pulses. The high affinity GH-binding protei n (GHBP) reportedly has an important role in enhancing the growth-prom oting action of GH, Levels of GHBP are characteristic for an individua l and increase only slightly as puberty progresses. It has been hypoth esized that each individual adjusts GH production to a level appropria te for his GHBP environment. The withdrawal of gonadal steroids that o ccurs in children with central precocious puberty (CPP) treated with L H-releasing hormone agonist (LHRHa) therapy results in a decrease in g rowth velocity (GV) and GH secretion. This study was performed to dete rmine the effect of treatment of CPP with the LHRHa leuprolide acetate for depot suspension on CH secretion and levels of GHBP. Six girls an d one boy with CPP were studied before and 6 months after treatment wa s initiated. Within 6 months of initiation of therapy, there was a sig nificant decline in GV, from 8.9 +/- 3.2 to 5.4 +/- 2.0 cm/yr (P < 0.0 5). Twelve-hour mean nocturnal GH levels decreased significantly from 8.6 +/- 3.5 to 5.1 +/- 2.3 mu g/L (P < 0.05). This occurred via a decr ease in the amplitude of GH pulses as the number of peaks remained 4.6 and 4.1/12 h. Individual levels of GHBP were variable and reflect the wide range of levels observed in normal children. Although GV and GH levels decreased substantially, mean GHBP levels remained unchanged at 139.9 +/- 46.0 and 152 +/- 39.8 pmol/L. In children with CPP, within 6 months of LHRHa therapy, the decrease in GV occurs via a decrease in nocturnal GH secretion as levels of GHBP remain unchanged. In childre n with CPP, the withdrawal of gonadal steroids may inhibit the child's ability to secrete the GH appropriate for his/her GH/GHBP milieu.