The growth hormone response to hexarelin in patients with different hypothalamic-pituitary abnormalities.
We evaluated the GH-releasing effect of hexarelin (Hex; 2 microg/kg, i.v.) and GHRH (1 microg/kg, i.v.) in 18 patients (11 males and 7 females, aged 2.5-20.4 yr) with GH deficiency (GHD) whose hypothalamic pituitary abnormalities had been previously characterized by dynamic magnetic resonance imaging (MRI). Ten patients had isolated GHD, and 8 had multiple pituitary hormone deficiency. All patients were receiving appropriate hormone replacement therapy. Twenty-four prepubertal short normal children (11 boys and 13 girls, aged 5.9-13 yr, body weight within +/-10% of ideal weight) served as controls. MRI studies revealed an ectopic posterior pituitary at the infundibular recess in all patients. A residual vascular component of the pituitary stalk was visualized in 8 patients with isolated GHD (group 1), whereas MRI showed the absence of the pituitary stalk (vascular and neural components) in the remaining 10 patients (group 2), of whom 8 had multiple pituitary hormone deficiency and 2 had isolated GHD. In the short normal children, the mean peak GH response to GHRH (24.8 +/- 4.4 microg/L) was significantly lower than that observed after Hex treatment (48.1 +/- 4.9 microg/L; P < 0.0001). In the GHD patients of group 2, the mean peak GH responses to GHRH (1.4 +/- 0.3 microg/L) and Hex (0.9 +/- 0.3 microg/L) were similar and markedly low. In the patients of group 1, the GH responses to GHRH (8.7 +/- 1.3 microg/L) and Hex (7.0 +/- 1.3 microg/L) were also similar, but were significantly higher that those observed in group 2 (P < 0.0001). In the whole group of patients, a significant correlation was found between the GH peaks after Hex and those after GHRH (r = 0.746; P < 0.0001). In this study we have confirmed that the integrity of the hypothalamic pituitary connections is essential for Hex to express its full GH-releasing activity and that Hex is able to stimulate GH secretion in patients with GHD but with a residual vascular component of the pituitary stalk.
Maghnie
M
M
Clinica Pediatrica, Policlinico S. Matteo, Universitá di Pavia, Italy.
Spica-Russotto
V
V
Cappa
M
M
Autelli
M
M
Tinelli
C
C
Civolani
P
P
Deghenghi
R
R
Severi
F
F
Loche
S
S
D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D005260:Female; D006133:Growth Substances / Q000627:therapeutic use*; D019382:Human Growth Hormone / Q000172:deficiency / Q000378:metabolism*; D006801:Humans; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects*; D008279:Magnetic Resonance Imaging; D008297:Male; D009842:Oligopeptides / Q000627:therapeutic use*; D010907:Pituitary Hormones / Q000172:deficiency*; D012636:Secretory Rate / Q000187:drug effects
D006133:Growth Substances; D009842:Oligopeptides; D010907:Pituitary Hormones; C086184:hexarelin; D019382:Human Growth Hormone