| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Endocrine Care |
Departments of Pediatrics (M.M., F.C., M.A.), Biometry-Scientific Direction (C.T.), and Servizio Analisi Chimico Cliniche (M.A.), IRCCS Policlinico S. Matteo, University of Pavia, I-27100 Pavia; and Division of Endocrinology (G.A., E.G.), Department of Internal Medicine, University of Turin, 10126 Turin, Italy
Address all correspondence and requests for reprints to: Mohamad Maghnie, M.D., Ph.D., Department of Pediatrics, IRCCS Policlinico S. Matteo, Viale Golgi 2, 27100 Pavia, Italy. E-mail: . maghnie{at}smatteo.pv.it
Abstract
We evaluated the GH-releasing effect of GHRH plus arginine (ARG) in 36 patients (22 males and 14 females) with acquired GH deficiency including idiopathic inflammatory pituitary stalk thickness (n = 15), Langerhans cell histiocytosis (LCH) affecting the hypothalamic-pituitary area (n = 11), and craniopharyngioma (n = 10). All of the patients (mean age, 9.6 ± 3.1 yr; range, 5.6–20.8) showed GH response less than 10 µg/liter after 2 pharmacological stimuli and were tested with GHRH plus ARG at a mean age of 11.2 ± 4.1 yr. Twenty-nine patients had vasopressin deficiency, 10 had TSH deficiency, 8 had gonadotropin deficiency, and 4 had ACTH deficiency.
The median peak GH response to insulin test was 2.1 µg/liter (range, 1.1–2.9), whereas it was 1.5 µg/liter (range, 1.3–2.4) after ARG. The median peak GH response to insulin was significantly lower in the patients with craniopharyngioma (1.4 µg/liter; range, 0.8–1.7) than in the patients with idiopathic pituitary stalk thickness (2.2 µg/liter; range, 1.0–2.4) or with LCH (2.6 µg/liter; range 2.0–4.3, P = 0.02). The median peak GH response to ARG was significantly lower in the patients with idiopathic inflammatory pituitary stalk thickness (1.3 µg/liter; range, 0.8–1.8) than in those with craniopharyngioma (1.5 µg/liter; range, 1.1–1.6) or with LCH (2.8 µg/liter; range, 1.9–3.2, P = 0.00007).
The median peak GH response after GHRH plus ARG was significantly lower in the overall patient population (8.3 µg/liter; range, 4.4–28.4) than in the age-matched controls (49.8 µg/liter; range, 39.9–81.6, P < 0.00001). The median peak GH response was significantly lower in the patients with craniopharyngioma (4.6 µg/liter; range, 3.6–6.3) than in those with LCH (8.9 µg/liter; range, 4.4–28.4) or with idiopathic pituitary stalk thickness (12.6 µg/liter, range, 6.4–24, P = 0.07). Ten patients had a GH response of more than 20 µg/liter after GHRH plus ARG. There was a trend toward a decrease in peak GH response to GHRH plus ARG (r = -0.57, P = 0.06) as patient age increased. For cut-off values of 20 µg/liter, the sensitivity of GHRH plus ARG was 75% (95% CI, 57.8–87.9%) and the specificity was 96.4% (95% CI, 89.9–99.2%); whereas, for cut-off values of 24.2 µg/liter, sensitivity was 86.1% (95% CI, 70.5–95.3%), and specificity was 95.2% (95% CI, 88.2–98.7%). The median IGF-I level did not differ between the children with idiopathic pituitary stalk thickness (57 µg/liter; range, 46–68), those with LCH (55 µg/liter; range, 34–63), and those with craniopharyngioma (41 µg/liter; range, 39–49).
The present study confirmed the diagnostic potential of the GHRH-plus-ARG test in children with acquired GH deficiency caused by hypothalamic-pituitary lesion. It stimulates GH secretion to a greater extent in those patients with GH deficiency with primary involvement of the hypothalamic area, e.g. patients with idiopathic pituitary stalk thickness or LCH, than in those with both hypothalamic and pituitary lesion, as in craniopharyngioma. In some patients, the GHRH-plus-ARG test stimulates GH response to a so-called: normal value, suggesting that pituitary responsiveness to GHRH plus ARG may fail to recognize acquired GHD. Finally, the number of pituitary hormone deficits and the patient’s age affect the GH response to GHRH plus ARG.
THE DIAGNOSIS OF GH deficiency during childhood is based on clinical features, biochemical studies, imaging findings, and (recently, in selected cases) on molecular analysis. The diagnosis can be straightforward, and the child may present the classical phenotype, such as truncal adiposity with fat dimpling, small genitalia and cryptorchidism in the male, frontal bossing and midfacial hypoplasia, short stature, and progressive growth failure; hypoglycemia may occur occasionally. Any test for GH evaluation in these cases is only confirmatory. These features, however, do not necessarily constitute the rule; and even in some genetic forms of GH deficiency, such as GHRH receptor mutation, this phenotype is absent.
Conventionally, two tests have been used to assess the GH axis, in the expectation that this might reduce the rate of false-positive results. The diagnosis of GH deficiency, however, remains puzzling because of certain factors, such as the lack of normal age-related reference values for serum GH, the use of both arbitrary cut-off levels (between 7 and 10 µg/liter) and of different pharmacological GH stimulation tests with poor reproducibility and many false-negative responses in normal children (1, 2, 3). In the absence of a gold standard, a limited number of provocative agents [including insulin, arginine (ARG), clonidine, glucagon, and L-dopa] should be used as recommended by recent consensus guidelines (4). Insulin-induced hypoglycemia [insulin tolerance test (ITT)], one of the most reliable provocative tests for the diagnosis of GH deficiency (5, 6), however, is associated with frequent symptomatic hypoglycemia in the great majority of patients with permanent GH deficiency, as confirmed in one of our recent studies (7). Thus, alternative provocative tests are needed for patients in whom ITT is contraindicated, including those with central nervous system involvement (for example, children with organic GH deficiency). The combination of GHRH plus ARG, based on its high specificity, has been found to be of value in children for the diagnosis of mainly idiopathic GH deficiency, provided appropriate cut-off limits are applied (4). Indeed, we recently reported that the GHRH-plus-ARG test is reliable for the diagnosis of GH deficiency in both children and adults with congenital hypopituitarism, without any significant side effects (8), suggesting that it is safe for the evaluation of GH status.
The aim of this study was to investigate the diagnostic role of the GHRH-plus-ARG test in patients with acquired GH deficiency. To this end, we evaluated the GH-releasing effect of GHRH plus ARG, compared with classical pharmacological tests, in 36 patients diagnosed, by means of magnetic resonance imaging (MRI), with central nervous system involvement, including idiopathic pituitary stalk thickness, Langerhans cell histiocytosis (LCH) affecting the hypothalamic-pituitary region, and craniopharyngioma.
Subjects and Methods
The study population was composed of 36 patients (mean age at the start of the study was 9.6 ± 3.1 yr; range, 5.6–20.8) with acquired GH deficiency including idiopathic pituitary stalk thickness (n = 15), LCH affecting the hypothalamic-pituitary region (n = 11), and craniopharyngioma (n = 10).
All patients had a GH response less than 10 µg/liter after at least 2 pharmacological stimuli [insulin (n = 31), ARG (n = 33), and clonidine, L-dopa, GHRH, sequential ARG-plus-insulin test, and glucagon (n = 8)]. The following multiple pituitary hormone deficiencies were documented: vasopressin (n = 29 patients, 15 with idiopathic pituitary stalk thickness, 11 with LCH, and 3 with craniopharyngioma), TSH (n = 10 patients, 1 with idiopathic pituitary stalk thickness, 2 with LCH, and 7 with craniopharyngioma), FSH/LH (n = 8 patients, 3 with idiopathic pituitary stalk thickness, 2 with LCH, and 3 with craniopharyngioma), and ACTH (n = 4 patients, all with craniopharyngioma); all patients were receiving appropriate hormonal replacement treatment.
The patients showed a progressive growth failure, with a mean height SD score of -0.9 ± 1.4 at the time of presentation; bone age was 7.9 ± 2.7 yr, and body mass index (kg/m2) was 19 ± 3.5. In particular, GH function was studied after administration of: ARG in 33 patients [0.5 g/kg body weight (BW), L-ARG monohydrochloride, given iv, over 30 min], insulin in 31 patients (0.1 U/kg BW, iv bolus), clonidine in 2 patients (0.15 mg/m2, orally), L-dopa in 2 patients (500 mg/1.73 m2, orally), glucagon in 1 patient (1 mg, im), GHRH in 1 patient (1 µg/kg BW, iv bolus), and sequential ARG-plus-insulin test in 1 patient. The blood samples for GH determinations were obtained at 0, 30, 60, 90, and 120 min after ARG, insulin, and L-dopa and at +150 and 180 min after glucagon and clonidine. GH peak between 5.0–9.9 µg/liter was found in 2 patients, whereas the remaining 34 patients had GH peak values less than 5.0 µg/liter.
MRI technique, with the use of contrast medium as previously described (4), revealed the following: hypothalamic-pituitary mass compatible with craniopharyngioma in 10 patients, subsequently confirmed after surgical biopsy; pituitary stalk thickness in 21 patients, 15 of whom had idiopathic likely inflammatory pituitary stalk thickness (9); and pituitary stalk thickness LCH-dependent in 6 patients; in the remaining 5 LCH patients, MRI did not reveal pituitary stalk lesions, suggesting hypothalamic involvement. The diagnosis of idiopathic pituitary stalk thickness was based on MRI findings of large pituitary stalk in the absence of other imaging or laboratory markers of specific diseases, including LCH, sarcoidosis, tuberculosis, germinomas, or systemic disorders. Biopsy-proven LCH at the level of skin or bone lesions was obtained in all affected patients.
All subjects were tested with GHRH (GHRH 1–29; GEREF, Serono, Italy; 1 µg/kg BW iv at time 0) plus ARG (0.5 g/kg BW, L-ARG monohydrochloride by iv, from time 0 over 30 min). The study was approved by the Department of Pediatrics Institutional Review Board, and written informed consent was obtained from the parents and (when possible) from the patients. Blood samples were drawn from an indwelling catheter inserted in an antecubital vein at -15 min and at times 0, 15, 30, 45, 60, 75, and 90 min. All studies started between 0800 and 0900 h, after the patients had fasted overnight. Bone age and serum IGF-I concentration were determined in all patients at the time of diagnosis.
Thirty patients were tested with GHRH plus ARG at the time of diagnosis of GH deficiency (median age, 8.9 yr; range, 5.8–21.3), and six were tested at the median point of 7.4 yr (range, 5.8–12.1) after diagnosis at a median age of 17.3 yr (range, 13.4–19.9). The main clinical findings are summarized in Tables 1
, 2, and 3.
|
|
|
Serum GH levels were measured by fluoroimmunoassay using a commercial kit (Auto DELFIA human GH, EG&G; Wallac, Inc. Oy, Turku, Finland). The intra- and interassay coefficients of variation were: 5.1% and 2.5%, at 0.430 mU/liter, 2.7% and 2.1% at 5.0 mU/liter, and 2.2% and 1.4% at 21.1 mU/liter. Cross-reactivity was less than 0.001% for PRL and human placental lactogen.
IGF-I was measured by RIA using a commercial kit (SM-C-RIA-CT; Biosource Technologies, Inc. SA, Nivelles, Belgium). The intra- and interassay coefficients of variation were: 6.1%, 4.1%, and 4.7% at 54.2 ± 3.3 µg/liter, 194 ± 8 µg/liter, and 491 ± 2 µg/liter; 9.9%, 9.6%, and 9.3% at 121 ± 11 µg/liter, 251 ± 24 µg/liter, and 494 ± 46 µg/liter, respectively. The sensitivity of the assay was 0.25 ± 0.1 µg/liter. Normal age-related values, for our laboratory, of either sex are: 1–3 yr, 30–120 µg/liter; 3–6 yr, 35–145 µg/liter; 6–9 yr, 75–195 µg/liter; 9–12 yr, 95–320 µg/liter; 12–15 yr, 160–340 µg/liter; and 15–21 yr, 210–520 µg/liter).
Statistical analysis
Comparisons between groups were performed using the Mann-Whitney U test (between two groups) or Kruskal-Wallis ANOVA analysis (for more than two groups). P < 0.05 was considered statistically significant. All tests were two-sided; data are given as the mean (SE) or as medians and ranges when appropriate (interquartile). Analyses were performed with Statistica for Windows 1998 software (StatSoft, Inc., Tulsa, OK)
Results
GH responses to provocative tests
The median GH response, after ITT, was 2.1 µg/liter [range, 1.1–2.9 µg/liter (n = 31)], and there was a significant difference between the patients affected by craniopharyngioma [1.4 µg/liter; range, 0.8–1.7 (n = 9)], those affected by idiopathic pituitary stalk thickness [2.2 µg/liter; range, 1.0–2.4 (n = 12)], and those with LCH [2.6 µg/liter; range, 2.0–4.3 (n = 10), P = 0.02].
The median GH response after ARG test was 1.5 µg/liter [range, 1.3–2.4 (n = 33)]. The median GH response was significantly lower in the patients with idiopathic pituitary stalk thickness [1.3 µg/liter; range, 0.8–1.8 (n = 12)] and in those affected by craniopharyngioma [1.5 µg/liter; range, 1.1–1.6 (n = 10)] than in the LCH patients [2.8 µg/liter; range, 1.9–3.2 (n = 11), P = 0.00007].
The median GH response after GHRH plus ARG was significantly lower in the patient population [8.3 µg/liter; range, 4.4–21.4 (n = 36)], compared with the age-matched control group [49.8 µg/liter; range, 39.9–81.6 (n = 84), P < 0.00001]. The median GH peak was lower in the patients with craniopharyngioma (4.6 µg/liter; range, 3.6–6.3) than in those with LCH (8.9 µg/liter; range, 4.4–28.4) and in those affected by idiopathic pituitary stalk thickness (12.6 µg/liter; range, 6.4–24; P = 0.07) (Fig. 1).
|
For cut-off values of 20 µg/liter, the sensitivity of GHRH plus ARG was 75% (95% CI, 57.8–87.9%), and the specificity was 96.4% (95% CI, 89.9–99.2%); whereas for cut-off values of 24.2 µg/liter, there was a higher sensitivity of 86.1% (95% CI, 70.5–95.3%) and equal specificity of 95.2% (95% CI, 88.2–98.7%).
The median serum IGF-I levels were 53 µg/liter (range, 41–64). The median IGF-I level did not differ between the children with idiopathic pituitary stalk thickness (57 µg/liter; range, 46–68), those with LCH (55 µg/liter; range, 34–63), and those with craniopharyngioma (41 µg/liter; range, 39–49).
Discussion
The present study shows that the GH response to GHRH plus ARG in children or adolescents with acquired GH deficiency is quantitatively different from that obtained after ITT or ARG. In particular, GHRH plus ARG induced an increase in serum GH concentrations that was much higher in patients with hypothalamic and/or pituitary stalk involvement, i.e. idiopathic inflammatory pituitary stalk thickness and LCH, than in those with craniopharyngioma. Indeed, the latter had negligible GH response to GHRH plus ARG as well as to ITT and to ARG, suggesting that the failure of GHRH plus ARG to stimulate GH secretion in craniopharyngioma is likely related to an additional intense involvement of the pituitary gland.
GHRH plus ARG is one of the most powerful provocative tests for GH secretion (5, 10, 11) and, unlike classical provocative tests (including ITT), it shows good intraindividual reproducibility (11); it may be of value in the diagnosis of GH deficiency, provided that appropriate cut-off limits are applied (4). In fact, it has been shown that testing with GHRH plus ARG distinguishes normal subjects from those with multiple pituitary hormone deficiency and that it is as sensitive as ITT for the diagnosis of GH deficiency in adults and in older adolescents (11, 12, 13). These data have been confirmed recently, by our group, in patients with congenital hypopituitarism, showing that the GH response to GHRH plus ARG is clearly impaired, both in children and adults with multiple anterior pituitary deficits and MRI evidence of pituitary stalk agenesis (8). The diagnostic value of this test, however, has not been adequately studied or reported in children or adolescents with acquired GH deficiency.
The present findings show that the GH response to GHRH plus ARG is similar to that obtained with ITT in patients with either craniopharyngioma or with idiopathic pituitary stalk thickness and LCH but with multiple pituitary hormone deficits. Our data confirm that the sensitivity and specificity of GHRH plus ARG are not dissimilar from that reported for ITT (6, 14) and that, therefore, GHRH plus ARG may be an appropriate alternative test when ITT is contraindicated and when assessment of GH secretion is required. However, GHRH plus ARG induced a considerable pituitary GH releasable pool, as shown by the peak GH level of more than 20 µg/liter in 10 patients, 9 of whom had idiopathic pituitary stalk thickness and LCH. This results in an overall level of 25% of false negatives, a statistic similar to the false positives resulting from the ITT test, and this suggests that these patients should not be completely segregated from normal subjects on the basis of peak GH response of more than 20 µg/liter. In our study, the use of GHRH plus ARG with a normal peak value of more than 20 µg/liter would have incorrectly classified 10 of 36 affected patients, whereas a peak value of 24.2 increased sensitivity to 86%, with a recovery of 5 affected patients, suggesting that GHRH plus ARG does not definitively rule out impaired GH response to ITT or ARG, at least in these patients.
In the present study, the pattern of GH response after GHRH plus ARG is not dissimilar to that reported by our group in LCH patients with GH deficiency in whom the GH increase after GHRH was compatible with hypothalamic involvement (15). This interpretation is in agreement with the widely accepted theory that the anterior pituitary is spared by LCH granulomatosis (16) and by the reversal of low GH response after chronic GHRH administration in Hand-Schuller-Christian disease (17), suggesting that alterations may be confined to the hypothalamus. In our study, the GH responses to GHRH plus ARG in the patient population were significantly lower than those obtained in normal subjects, suggesting that partial impairment of the GH releasable pool reflects a possible additional pituitary involvement, also in patients with idiopathic pituitary stalk thickness and LCH, as intimated by the progressive shrinkage of the pituitary gland reported in such patients (9).
Although a current consensus endorses reliance on a single test for the diagnosis of GH deficiency in the course of organic pituitary diseases and/or additional pituitary hormone deficiencies, we believe, based on the results of our study, that a single test is not sufficient for a correct diagnosis in the case of the GHRH-plus-ARG test during childhood and adolescence. It is advisable to point out that a GH response more than 20 µg/liter was obtained in subjects younger than 18 yr, suggesting that this test may be much more reliable in older patients. This might be secondary to the progressive deterioration of pituitary function rather than to age, based on the observation of evolving pituitary damage previously reported in such patients (9, 18). The pattern of GH response shown in Fig. 2 is in agreement with the low GH response after GHRH plus ARG previously reported in young adults with childhood-onset organic GH deficiency (16).
|
Acknowledgments
Footnotes
This work was supported in part by a grant from the IRCCS Policlinico S. Matteo, Pavia; Grant 116/98, 2618/GEN/2000; and by the Fondazione per lo studio delle malattie Endocrino-Metaboliche, Torino.
Abbreviations: ARG, Arginine; BW, body weight; ITT, insulin tolerance test; LCH, Langerhans cell histiocytosis; MRI, magnetic resonance imaging.
Received October 15, 2001.
Accepted February 21, 2002.
References
This article has been cited by other articles:
 |
|
 |
|
  G. Corneli, C. Di Somma, F. Prodam, J. Bellone, S. Bellone, V. Gasco, R. Baldelli, S. Rovere, H. J. Schneider, L. Gargantini, et al. Cut-off limits of the GH response to GHRH plus arginine test and IGF-I levels for the diagnosis of GH deficiency in late adolescents and young adults Eur. J. Endocrinol., December 1, 2007; 157(6): 701 - 708. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. di Iorgi, A. Secco, F. Napoli, C. Tinelli, A. Calcagno, N. Fratangeli, L. Ambrosini, A. Rossi, R. Lorini, and M. Maghnie Deterioration of Growth Hormone (GH) Response and Anterior Pituitary Function in Young Adults with Childhood-Onset GH Deficiency and Ectopic Posterior Pituitary: A Two-Year Prospective Follow-Up Study J. Clin. Endocrinol. Metab., October 1, 2007; 92(10): 3875 - 3884. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Bjork, K. Link, and E. M. Erfurth The Utility of the Growth Hormone (GH) Releasing Hormone-Arginine Test for Diagnosing GH Deficiency in Adults with Childhood Acute Lymphoblastic Leukemia Treated with Cranial Irradiation J. Clin. Endocrinol. Metab., November 1, 2005; 90(11): 6048 - 6054. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Maghnie, G. Aimaretti, S. Bellone, G. Bona, J. Bellone, R. Baldelli, C. de Sanctis, L. Gargantini, R. Gastaldi, L. Ghizzoni, et al. Diagnosis of GH deficiency in the transition period: accuracy of insulin tolerance test and insulin-like growth factor-I measurement Eur. J. Endocrinol., April 1, 2005; 152(4): 589 - 596. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. L. Germain-Lee, J. Groman, J. L. Crane, S. M. Jan de Beur, and M. A. Levine Growth Hormone Deficiency in Pseudohypoparathyroidism Type 1a: Another Manifestation of Multihormone Resistance J. Clin. Endocrinol. Metab., September 1, 2003; 88(9): 4059 - 4069. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. De Bellis, A. Bizzarro, M. Conte, S. Perrino, C. Coronella, S. Solimeno, A. M. Sinisi, L. A. Stile, G. Pisano, and A. Bellastella Antipituitary Antibodies in Adults with Apparently Idiopathic Growth Hormone Deficiency and in Adults with Autoimmune Endocrine Diseases J. Clin. Endocrinol. Metab., February 1, 2003; 88(2): 650 - 654. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Endocrinology | Endocrine Reviews | J. Clin. End. & Metab. |
| Molecular Endocrinology | Recent Prog. Horm. Res. | All Endocrine Journals |
