SERUM GROWTH HORMONE-BINDING PROTEIN IS UNCHANGED IN ADULT PANHYPOPITUITARISM

The role of GK in regulating GH-binding protein (GHBP) and GH receptor concentrations in humans is not clear. Studies performed mostly in ch ildren and on a minor scale in adults are somewhat controversial. The key question as to whether GKBP levels are altered in hypopituitarism before GH treatment is instituted remains unanswered. In this study, w e have selected a severely GH-deficient group of adult patients with p anhypopituitarism, acquired as a result of surgery and irradiation of hypothalamic-pituitary tumors, to evaluate the GHBP/receptor status by measuring GHBP activity in plasma. Twenty panhypopituitary patients ( 8 males and 12 females; age range, 20-74 yr) and 20 age (22-68 yr)- an d sex-matched normal subjects were studied. GH deficiency was confirme d by insulin-induced hypoglycemia and arginine infusion tests; the pea k GH response was less than 2 mu g/L. Plasma insulin-like growth facto r-I levels were below or in the low normal range (mean +/- SD, 88.3 +/ - 53.6 mu g/L) and were significantly different from insulin-like grow th factor-I (IGF-I) levels in the normal group (mean +/- SD, 189 +/- 4 9.8 mu g/L; P < 0.01).Plasma GHBP activity, measured using a GH-bindin g/gel chromatography assay, showed similar values in the GH-deficient group (mean +/- SD, 14.1 +/- 3.83%) and the control group (mean +/- SD , 13.7 +/- 3.79%), with no statistically significant difference. Neith er the intra- nor intergroup comparison of GHBP levels according to ag e and sex showed statistically significant differences or age trends. In the light of these data and considering that GHBP activity in plasm a probably reflects the GH receptor status in tissues, we may assume t hat the GH receptor was unaffected by chronic GH deficiency. These fin dings also support the previously reported concept that the GHBP/recep tor level is a relatively fixed determinant of growth, established ind ividually and independently of GH secretory status in early life, perh aps on a genetic basis.