Decreased Metabolic Clearance of Endogenous Growth Hormone and Specific Alterations in the Pulsatile Mode of Growth Hormone Secretion Occur in Prepubertal Girls with Turner's Syndrome*

Abstract

We have used deconvolution analysis to test the hypothesis that specific facets of GH secretion and clearance differ in young patients with Turner's syndrome and normal prepubertal girls. To this end, we sampled blood at 20-min intervals for 12 h overnight in 50 girls, 37 of whom had Turner's syndrome and 13 of whom were healthy Tanner stage I controls. Deconvolution analysis revealed that the half-life of endogenous GH in Turner's syndrome was significantly prolonged at 14 +/- 0.93 vs. 11 +/- 0.44 min in normal girls (P = 0.029). The number of significant GH secretory bursts was reduced in Turner's patients to 4.7 +/- 0.27 vs. 6.8 +/- 0.60 events/12 h in healthy girls (P less than 0.01). GH secretory burst half-duration was significantly prolonged in Turner's syndrome, viz. 23 +/- 1.3 vs. 15 +/- 0.87 min (controls; P less than 0.001). The changes in GH secretory burst frequency, duration, and half-life were specific, since neither the mass of GH secreted per burst nor the maximal rate of GH secretion attained per burst (amplitude of the secretion pulse) was significantly different in the 2 study groups. Thus, although 12-h GH secretion rates corrected for body weight were similar (3.9 +/- 0.76 in Turner's patients and 3.3 +/- 0.76 micrograms/L.kg/12 h in the control girls), equivalent GH production rates were achieved by different mechanisms in the 2 groups. We conclude that specific alterations in GH secretory burst frequency and duration and endogenous GH half-life can be documented in young girls with Turner's syndrome.