Clinical Enhanced Growth Hormone Responses to Growth Hormone Releasing Hormone in Male Type I Diabetic Patients
Summary In a previous paper we have demonstrated that growth hormone (GH) responses to growth hormone releasing hormone (GHRH) are higher in premenopausal normal women than in age matched healthy men. As in type I diabetes mellitus various disturbances of G H secretion have been reported, the aim of our study was to assess the effect of sex on basal and G H R H stimulated G H secretion in type I diabetes mellitus. In 21 female and 23 male type I diabetic patients and 28 female and 30 male control subjects G H levels were measured before and after stimulation with G H R H (1 ug/kg body weight i. v.) by radioimmunoassay. G H responses to G H R H were significantly higher in female than in male control subjects (p < 0.02), whereas the G H levels following G H R H stimulation were similar in female and male type I diabetic patients. G H responses to G H R H were significantly higher in the male type I diabetic patients than in the male control subjects (p < 0.001); in the female type I diabetic patients and the female control subjects, however, G H responses to G H R H were not statistically different. The absence of an effect of sex on G H R H stimulated G H responses in type I diabetes mellitus provides further evidence of an abnormal G H secretion in this disorder. Key words Growth Hormone — Growth Hormone Releasing Hormone — Type I Diabetes Mellitus — Sex Hormones — Sex Differences
Urdanivia and Cohen 1981). Beside the adverse effect of G H on metabolic control (Press, Tamborlane and Sherwin 1984a; Press, Tamborlane and Sherwin 1986), G H has been implicated in the pathogenesis of diabetic microvascular late complications (Lundbaek, Christensen, Jensen, Johansen, Olsen, Hansen, Orskov and Osterby 1970). Whereas in the past merely non-specific stimuli to test G H secretion were available, in the last few years growth hormone releasing hormone (GHRH) has been proved to be an efficient and safe diagnostic tool in the investigation of disorders of G H secretion (Thorner, Rivier, Spiess, Borges, Vance, Bloom, Rogol, Cronin, Kaiser, Evans, Webster, MacLeod and Vale 1983). In a previous paper we have demonstrated that in normal premenopausal women G H responses to G H R H are significantly higher than in matched healthy men (Lang, Schemthaner, Pietschmann, Kurz, Stephenson and Tempi 1987). In view of the various abnormalities in G H secretion in type I diabetes mellitus as mentioned above the aim of the present study was to assess the effect of sex on basal and G H R H stimulated G H levels in type I diabetes mellitus. Patients and Methods Subjects 44 non obese patients with classical type I diabetes mellitus and 58 non-obese normal subjects (28 females; mean age 29 ± 1 years body mass index: 21 + 1% and 30 males: mean age: 30 ± 1 years, body mass index 23 ± 1 %) were studied after giving informed consent. Clinical characteristics of the type I diabetic patients are summarized in Table 1. Age, diabetes duration and indices of metabolic control were similar in male and female type I diabetic patients. GHRH
Introduction Various data in the literature suggest that the regulation of growth hormone (GH) secretion in diabetes mellitus is abnormal. In type I diabetic patients, especially when metabolic control is poor, elevated G H levels have been found (Vigneri, Squatrito, Pezzino, Filetti, Branca and Polosa 1976). Furthermore, type I diabetic patients show a G H hyper-responsiveness to unspecific stimuli such as physical exercise (Hansen 1970) and a paradoxical G H response to TRH injection which does not occur in normal subjects (Schemthaner, Spona, Ludwig and Bieglmayer 1978; Dasmahapatra, Horm.metab.Res. 23(1991)379-382 © Georg Thieme Verlag Stuttgart • New York
GHRH tests were performed as described previously (Pietschmann, Schemthaner and Luger 1986) after an overnight fast with the subjects recumbent for at least two hours. In brief, blood samples were obtained before (— 30,0 minutes) and after (15,30,45,60 and 90 minutes) an i. v. bolus injection of 1 ug/kg body weight human GHRH (1-44; Bissendorf Peptides, Wedemark, Germany) diluted to 10 ml with 0.15MNaCl. Radioimmunoassays Serum GH levels were measured in duplicate by a commercially available radioimmunoassay (Tandem B HGH Hybritech, Belgium). The intra- and interassay coefficients of variation Received: 20 Apr. 1990
Accepted: 4 Febr. 1991 after revision
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P. Pietschmann, G. Schemthaner, J. Stephenson, I. Lang and H. Tempi II. Medizinische Universitatsklinik, I. Medizinische Abteilung der Krankenanstalt Rudolfstiftung, Ludwig Boltzmann Institut fur Klinische Endokrinologie, Vienna, Austria
P. Pietschmann, G. Schernthaner, J. Stephenson, I. Lang and H. Tempi
Horm. metab. Res. 23 (1991)
(CV) were 3.8% and 5.2%, respectively (at 8.1 ng/ml and 7.8 ng/ml respectively). The minimal detectable concentration was 0.2 ng/ml. The A GH (= peak GH level after GHRH stimulation minus basal GH level) was calculated for each patient. In addition, basal serum levels of estradiol (Radioimmunoassay System Laboratories, Inc, CA; interassay CV 3.5% interassay CV 5.0%) and testosterone (Radioassay Systems Laboratories, intraassay, CV: 5.0% interassay CV 7.0 %) were measured. Statistics The results are expressed as the mean + SEM. Student's t-test and Pearson correlation coefficient were used for statistical analysis.
A G H levels in the male type I diabetic patients were significantly higher than those of the male control subjects (A G H 20.2 + 3.1 ng/ml vs. 7.7 ± 0.9 ng/ml, p < 0.001); in the female type I diabetic patients the A G H levels were higher than in the female control subjects, however the differences were not statistically significant (21.3 + 4.3 ng/ml vs. 13.1 +2.1 ng/ml, N . S.). Likewise, the area under the GH-response curves (AUC) was significantly greater in the male type I diabetic patients than in the male control subjects (78.4+12.3 ng/15 min. x ml vs. 31.8 + 3.8 ng/15 min. x ml; p < 0.005), whereas the AUC in the female type I diabetic patients and the female controls were not statistically different (94.0 + 20.1 ng/15 min. x ml vs. 70.4+11.1 ng/15 min. x ml).
Basal and G H R H stimulated G H levels in the type I diabetic patients and the control subjects are shown in Figure 1. Both in type I diabetic patients and control subjects basal G H levels were significantly higher in the female than in the male subjects. Whereas the A G H levels in the female normal subjects were significantly higher than in the male controls (A G H 13.1 + 2 . 1 ng/ml vs. 7.7 + 0.9 ng/ml, p < 0.03) A G H levels were similar in female and male type I diabetic patients (21.3+4.3 ng/ml vs. 20.2 + 3.1 ng/ml, N. S.).
Table 1 Clinical characteristics of female and male type I diabetic patients.
age (years) body mass index (kg/m2 fasting plasma glucose (mg/dl) HbA1c*(%) diabetes duration (years)
females (n = 21)
males (n = 23)
30 ± 2 22 + 1 203 ±21 8.4 + 0.5 13 + 2
31 ± 3 23±1 220 + 21 9.0 ±0.3 13±2
When the data of female and male subjects were combined, the G H responses to G H R H (A GH) were significantly higher in the type I diabetic patients than in the control subjects (A G H 20.7 + 2.6 ng/ml vs. 10.3+1.2 ng/ml, p < 0.001). Estradiol and testosterone
Both in the female and male type I diabetic patients serum estradiol levels were lower than in the normal subjects (Table 2) whereas serum levels of testosterone in the
Table 2 Serum levels of estradiol and testosterone in the male and female type I diabetic patients (DM) and the corresponding control subjects (CO). a: pc < 0.02; b: pc < 0.001. Estradiol (pg/ml) DM, male CO, male DM, female CO, female
23.7 ±4.7 115.0 ±24.3 80.5 ±21.4 157.0 ±22.3
Testosterone (ng/dl) b
639.0 ±45.5 624.4 ±41.6 87.4 ±31.8 57.1 ±5.9
Fig. 1 Growth hormone responses to growth hormone releasing hormone in female (O) and male ( • ) type I diabetic patients (left panel) and female (O) and male ( • ) control subjects (right panel). Asterisks indicate statistical different values in female vs. male subjects/patients. *p