GH Reserve Research Articles

Utility of serum IGF-1 for diagnosis of growth hormone deficiency following traumatic brain injury and sport-related concussion

BackgroundGrowth hormone deficiency (GHD) is a potential consequence of traumatic brain injury (TBI), including sport-related concussion (SRC). GH stimulation testing is required for definitive diagnosis; however, this is resource intensive and can be associated with adverse symptoms or risks. Measurement of serum IGF-1 is more practical and accessible, and pituitary tumour patients with hypopituitarism and low serum IGF-1 have been shown to have a high probability of GHD. We aimed to evaluate IGF-1 measurement for diagnosing GHD in our local TBI population.MethodsWe conducted a retrospective chart review of patients evaluated for GHD at the TBI clinic and referred for GH stimulation testing with insulin tolerance test (ITT) or glucagon stimulation test (GST) since December 2013. We obtained demographics, TBI severity, IGF-1, data pertaining to pituitary function, and GH stimulation results. IGF-1 values were used to calculate z-scores per age and gender specific reference ranges. Receiver operator curve analysis was performed to evaluate diagnostic threshold of IGF-1 z-score for determining GHD by GST or ITT.ResultsSixty four patient charts were reviewed. 48 patients had mild, six had moderate, eight had severe TBI, and two had non-traumatic brain injuries. 47 patients underwent ITT or GST. 27 were confirmed to have GHD (peak hGH < 5 μg/L). IGF-1 level was within the age and gender specific reference range for all patients with confirmed GHD following GH stimulation testing. Only one patient had a baseline IGF-1 level below the age and gender specific reference range; this patient had a normal response to GH stimulation testing. ROC analysis showed IGF-1 z-score AUC f, confirming lack of diagnostic utility.ConclusionBaseline IGF-1 is not a useful predictor of GHD in our local TBI population, and therefore has no value as a screening tool. TBI patients undergoing pituitary evaluation will require a dynamic test of GH reserve.

Pegvisomant-primed glucagon stimulation test in assessing GH reserve and GH/IGF kinetics in adults suspected of GH deficiency.

The accuracy of the glucagon stimulation test(GST) in diagnosing adult GH deficiency (GHD) has recently been questioned. Because pegvisomant (PegV)increases endogenous GH secretion, we hypothesized that priming PegV to the GST (PegV-GST) 72 h beforehand would improve the diagnostic accuracy of this test. This pilot study aimed to prospectively compare PegV-GST to two other diagnostic tests for adult GHD. Adults suspected of GHD underwent PegVGST,GST and insulin tolerance test (ITT) in random order.Growth hormone levels (measured by a PegV insensitive assay) during PegV-GST, GST and ITT were compared,and acute effects of PegV on GH/IGF kinetics were assessed. Ten subjects with hypothalamic-pituitary disease and 1–4 pituitary hormone deficiencies were studied. Basal and peak GH levels with the PegV-GST were comparable to those of the GST and ITT. The five subjects that failed the GST and ITT were the same subjects that failed the PegVGST,using the peak GH cut point of<3 ng/mL for this test. After PegV priming, basal GH and GH binding protein(GHBP) increased (both P<0.01) and total IGF-I and bioactive IGF decreased (both P<0.05), whereas IGF-II and IGFBPs -1, -2 and -3 were unchanged compared to pre-PegV priming. Serum PegV levels correlated positively with basal GH, peak GH, IGFBP-1 and IGFBP-2 levels, and negatively with D bioactive IGF and DGHBP (all P<0.05). Single dose PegV administration in adults suspected of GHD increased basal GH and GHBP, with concomitant rapid fall in IGF-I levels and bioactive IGF. PegV priming did not appear to improve the diagnostic accuracy of the GST. Further studies involving larger subject numbers are needed to verify the clinical utility of PegV-GST in evaluating adult GHD.

Alström syndrome is associated with short stature and reduced GH reserve

Alström syndrome (ALMS) is a rare autosomal recessive monogenic disease included in an emerging class of genetic disorders called 'ciliopathies' and is likely to impact the central nervous system as well as metabolic and endocrine function. Individuals with ALMS present clinical features resembling a growth hormone deficiency (GHD) condition, but thus far no study has specifically investigated this aspect in a large population. Twenty-three patients with ALMS (age, 1-52years; 11 males, 12 females) were evaluated for anthropometric parameters (growth charts and standard deviation score (SDS) of height, weight, BMI), GH secretion by growth hormone-releasing hormone + arginine test (GHRH-arg), bone age, and hypothalamic-pituitary magnetic resonance imaging (MRI). A group of 17 healthy subjects served as controls in the GH secretion study. Longitudinal retrospective and prospective data were utilized. The length-for-age measurements from birth to 36months showed normal growth with most values falling within -0·67 SDS to +1·28 SDS. A progressive decrease in stature-for-age was observed after 10years of age, with a low final height in almost all ALMS subjects (>16-20years; mean SDS, -2·22±1·16). The subset of 12 patients with ALMS tested for GHRH-arg showed a significantly shorter stature than age-matched controls (154·7±10·6cm vs 162·9±4·8cm, P=0·009) and a mild increase in BMI (Kg/m(2) ) (27·8±4·8 vs 24·1±2·5, P=0·007). Peak GH after GHRH-arg was significantly lower in patients with ALMS in comparison with controls (11·9±6·9μg/l vs 86·1±33·2μg/l, P<0·0001). Severe GHD was evident biochemically in 50% of patients with ALMS. The 10 adult ALMS patients with GHD showed a reduced height in comparison with those without GHD (149·7±6·2cm vs 161·9± 9·2cm, P=0·04). MRIs of the diencephalic and pituitary regions were normal in 11 of 12 patients. Bone age was advanced in 43% of cases. Our study shows that 50% of nonobese ALMS patients have an inadequate GH reserve to GHRH-arg and may be functionally GH deficient. The short stature reported in ALMS may be at least partially influenced by impairment of GH secretion.

Recovery of pituitary function in the late-postoperative phase after pituitary surgery: results of dynamic testing in patients with pituitary disease by insulin tolerance test 3 and 12 months after surgery

The insulin tolerance test (ITT) is considered the gold standard for assessment of GH and ACTH reserve in patients with pituitary disease following pituitary surgery and is usually performed after 6-12 weeks. However, abnormal axes may not be completely recovered by then. The aim of this study was to evaluate dynamic testing 3 and 12 months after transsphenoidal pituitary surgery. Serial dynamic testing was performed in 36 patients (13 women, age 18-78) at 3 and 12 months after transsphenoidal surgery. Compared with 3-month results, median GH peak levels during ITT after 12 months increased by 38% (P<0.05). In patients initially classified as GH deficiency (GHD), median GH peak increased after 12 months by 23% (P<0.05). At 3 and 12 months, 36% (13/36) and 47% (17/36) were GH sufficient respectively. Median cortisol peak levels after 12 months increased by 17% (P<0.01) compared with 3-month ITT. In ACTH-insufficient (AI) patients, peak cortisol levels increased significantly by 12% (P<0.05) at 12 months, and in ACTH-sufficient patients, peak cortisol levels increased significantly by 13% (P<0.05). At 12 months, there was recovery from AI in 11% of the patients, and recovery from GHD in 11% of patients. Serial dynamic testing results in a change in classification by ITT results in a relevant proportion of patients. Dynamic testing should be repeated during follow-up.

Diagnostic utility of the glucagon stimulation test in comparison to the insulin tolerance test in patients following pituitary surgery

The glucagon stimulation test (GST) like the insulin tolerance test (ITT) stimulates both ACTH and GH secretion. However, there are limited data with modern assays on sensitivity and specificity for GST in comparison to ITT. The aim of this study was to evaluate the diagnostic utility of the GST for GH deficiency (GHD) and adrenal insufficiency (AI) in patients following pituitary surgery. ITT and GST were performed within 7 days in 49 patients at least 3 months after transsphenoidal surgery. Serum GH and cortisol were measured by Immulite 2000 assay (Siemens AG). Receiver-operating characteristic (ROC) analysis was performed to identify the thresholds for GST. In ITT, 18/49 cases were classified as AI. ROC analysis revealed a peak cortisol value >599 nmol/l in GST for adrenal sufficiency with 100% specificity and 32% sensitivity, and a peak cortisol <277 nmol/l with >95% specificity and 72% sensitivity for AI. Of the 49 subjects, 25 (51%) demonstrated levels between these cut-offs and could not be diagnosed by GST alone with sufficient accuracy. Regarding GHD, 21/49 cases were classified as insufficient by ITT. ROC analysis revealed a cut-off of 2.5 ng/ml with 95% sensitivity and 79% specificity. Of the 49 cases, seven (14%) were discordant in terms of defining GHD, with six subjects being treated for GHD according to GST although being sufficient in ITT. In our prospective series of patients with pituitary disease, GST is a potential alternative test for the assessment of GH reserve, but is a poor test for ACTH reserve. Test-specific cut-offs should be applied to avoid misinterpretation.

Prospective comparison of the glucagon stimulation test (GST) with the insulin tolerance test (ITT) in patients following pituitary surgery

Objective: The ITT is the gold-standard for assessment of GH and ACTH reserve but has certain contraindications. GH and cortisol responses of 95% sensitivity and 72% specificity for cortisol sufficiency. Using both upper and lower cut-off, 25/49 (51%) of subjects could not be diagnosed by GST alone and required further testing. Regarding GHD, 21/49 cases were classified as insufficient by ITT. ROC analysis revealed a cut-off of 2.5ng/ml with 95% sensitivity and 79% specificity. 7/49 (14%) cases were discordant in terms of defining GHD when comparing GST and ITT results, with 6 subjects being treated for GHD according to GST although being sufficient in ITT. Further analysis revealed, that the GST could be limited to 3h sampling period without any loss in accuracy. Conclusion: In our prospective series of patients with pituitary disease, GST is a potential alternative test for assessment of GH reserve, but poor for ACTH reserve, as demonstrated by comparison with the ITT. Test-specific cut-offs should be applied to avoid misinterpretation.

A Simple and Cost-Effective Approach to Assessment of Pituitary Adrenocorticotropin and Growth Hormone Reserve: Combined Use of the Overnight Metyrapone Test and Insulin-Like Growth Factor-I Standard Deviation Scores

The insulin tolerance test (ITT) is the gold standard for assessment of ACTH and GH reserve in patients with suspected hypopituitarism. It is labor intensive and costly. The objective of the study was to determine whether use of the overnight metyrapone test (OMT) and plasma IGF-I sd scores (SDS) could provide a cost-effective alternative to the ITT. This was a retrospective chart review. The study was conducted at a teaching hospital. Charts from 100 patients with organic pituitary disorders were reviewed. All underwent the OMT unless 0900 h plasma cortisol was less than 80 or greater than 450 nmol/liter when ACTH deficiency or ACTH sufficiency, respectively, was diagnosed. Patients were considered GH deficient if the age-related IGF-I SDS was less than -3 or if they had three or more other pituitary hormone deficiencies. Patients were considered GH sufficient if age-related IGF-I SDS was greater than the 95th centile established from patients with known GH deficiency. Thirty-three underwent an ITT. The proportion of patients in whom ACTH and GH reserve could be assessed using OMT/IGF-I SDS was measured. The concordance with results was obtained from ITT. Fifty-five patients were ACTH sufficient and 45 were ACTH deficient. Twenty-one were GH sufficient and 33 were GH deficient based on IGF-I SDS and other pituitary hormone deficiencies, whereas 46 could not be classified. There was near-uniform concordance between OMT/IGF-I SDS and ITT. Initial investigation using OMT/IGF-I SDS resulted in a significant cost saving. ACTH and GH reserve can be accurately and cost-effectively investigated using OMT/IGF-I SDS in approximately 50% of patients with organic pituitary disorders.

Prevalence of GH and other anterior pituitary hormone deficiencies in adults with nonsecreting pituitary microadenomas and normal serum IGF‐1 levels

GH is usually the first pituitary hormone to be affected following a pathological insult to the pituitary; however, data on the prevalence of GH deficiency in patients with nonsecreting pituitary microadenomas and normal serum IGF-1 levels are scarce. This study aims to evaluate the prevalence of GH and other anterior pituitary hormone deficiencies, and to determine whether microadenomas per se could be associated with reduced GH response rates to GHRH-arginine stimulation. Analytical, retrospective, two-site case-control study. Thirty-eight patients with nonsecreting pituitary microadenomas (mean size 4.2 mm) and normal serum IGF-1 levels were studied. Anterior pituitary function testing, including the GHRH-arginine test to examine GH reserve, was performed in all patients. Serum IGF-1 levels and peak GH levels in the patients that passed the GHRH-arginine test were compared with 22 age- and BMI-matched healthy controls. Nineteen patients (50%) failed the GHRH-arginine test and had higher body mass index (BMI) than those that passed the GHRH-arginine test and healthy controls. Peak GH levels in patients that passed the GHRH-arginine test were lower compared to healthy controls and 19 patients (50%) had at least one other pituitary hormone deficit. A negative correlation (r = -0.42, P < 0.01) between peak GH levels and BMI was identified, but no correlations were found between peak GH and serum IGF-1 levels. Our data demonstrated that a substantial number of patients with nonsecreting pituitary microadenomas failed the GHRH-arginine test despite normal serum IGF-1 levels, and had at least one other pituitary hormone deficiency, suggesting that nonsecreting microadenomas may not be clinically harmless. We therefore recommend long-term follow-up with periodic basal pituitary function testing, and to consider dynamic pituitary testing should clinical symptoms arise in these patients.

Growth hormone deficiency (GHD) in adult thalassaemic patients

Short stature and growth hormone deficiency (GHD) are frequent occurrences in thalassaemic children, while data on the prevalence of GHD in adult patients are lacking. Therefore, we elected to study the growth hormone and insulin-like growth factor-I (GH-IGF-I) axis in a large group of adult thalassaemic subjects. Cross-sectional study on the prevalence of GHD in 94 adult thalassaemic patients (69 with thalassaemia major and 25 with thalassaemia intermedia, 39 men and 55 women, aged 31.5 +/- 6.8 years, on sex steroid replacement when necessary). All patients underwent GHRH (1 microg/kg as an i.v. bolus) plus arginine (0.5 g/kg as a 30 min i.v. infusion) testing. Severe GHD was defined by GH peaks lower than 9 microg/l, whereas partial GHD was defined by GH peaks ranging from 9-16.5 microg/l. Blood samples for IGF-I, ferritin and pseudocholinesterase measurements were collected. Urinary free cortisol (UFC) levels were also assayed. Severe GHD was demonstrated in 21 of the 94 patients (22.3%), while 18 additional patients (19.1%) displayed partial GHD. GH peaks were positively correlated with IGF-I standard deviation score (SDS) (r = 0.22, P < 0.05), although 1 of the 21 patients with severe GHD showed normal IGF-I SDS values, and 44 of the 55 patients with normal GH reserve displayed low IGF-I SDS. A strong positive correlation (r = 0.48, P < 0.0001) between IGF-I SDS and pseudocholinesterase was identified. No correlations were found between ferritin and UFC levels on the one hand and GH peaks and IGF-I SDS on the other. Findings from this study demonstrate that GHD, either partial or severe, is not a rare occurrence in adult thalassaemic patients. GHD is associated with a higher prevalence of low serum IGF-I levels, recorded also in patients with normal GH secretion. The lack of correlation between ferritin and both GH peaks and IGF-I SDS suggests that mechanisms additional to iron overload, whose relevance cannot however be definitely ruled out, play a role in the pathophysiology of somatotrophin-somatomedin deficiency in this clinical condition. The positive correlation between IGF-I SDS on the one hand and GH peaks and pseudocholinesterase values on the other hand indicates that reduced liver protidosynthetic activity, in addition to somatotrophin secretory status, is a major determinant of the impaired IGF-I production in thalassaemia. Therefore biosynthetic GH replacement therapy in GH-deficient thalassaemic adults is worth considering.

Combining Growth Hormone Releasing Hormone-Arginine and Synacthen Testing Diminishes the Cortisol Response

The GHRH/arginine test and short synacthen test (SST) have been validated as safe alternatives to the insulin tolerance test for the assessment of the GH reserve and hypothalamic-pituitary-adrenal axis integrity, respectively. However, these two tests are usually performed separately. The objective was to see whether the synacthen and GHRH/arginine tests could be combined to save time and blood samples and minimize inconvenience to patients. Twenty-four consecutive patients with adult onset pituitary disease requiring pituitary function testing were randomized to receive sequentially and in random order a SST, a GHRH/arginine test, and a combined SST and GHRH/arginine test on three different visits separated by at least 1 wk. There was no difference in basal cortisol or ACTH values for the SST done alone or during the combined test. However, when GHRH/arginine was given with synacthen, patients had a lower peak cortisol response with a mean difference of 116 nmol/liter (95% confidence interval, 52.54 to 179.37; P < 0.001), and one patient with a normal response on the SST had a subnormal cortisol response in the combined test. Similar lower peak cortisol responses were observed in males and females with combined test. The difference between the peak cortisol responses showed no significant correlation with age (r = 0.123; P = 0.58) or with the body mass index (r = -0.376; P = 0.09). There was no difference in GH measurements between the GHRH/arginine test done alone or in combination with the SST. Combining the SST and GHRH/arginine test results in a lower cortisol response to synacthen. For this reason, the combined test cannot be recommended to assess the integrity of cortisol and GH reserve using current diagnostic criteria.

A new mutation in the growth hormone-releasing hormone receptor gene in two Israeli Arab families

Mutations in the GHRH receptor gene (GHRH-R) are emerging as a common cause of familial isolated GH deficiency (IGHD). We searched for GHRH-R mutations in 10 patients with IGHD of Israeli-Arab origin, belonging to two highly consanguineous families. Analysis of the 13 coding exons, the intron-exon boundaries, and the proximal promoter of the GHRH-R was performed by denaturing gradient gel electrophoresis. Abnormally migrating bands were sequenced. The newly found mutation was inserted into GHRH-R cDNA. Wild type and mutant receptor were expressed in Chinese hamster ovary (CHO) cells, and the cAMP response to GHRH was measured. All patients were homozygous for a novel GHRH-R missense mutation in exon 11 that replaces arginine with cysteine (R357C). Functional assay demonstrated complete inactivity of the mutant receptor in vitro. The prevalence of the mutant allele in the Israeli-Arab population was found to be 2%. All the patients had low but detectable GH reserve, proportionate short stature, and growth retardation since early childhood, with good growth response to GH treatment. Magnetic resonance imaging, performed in 3 patients, revealed a normal sized anterior pituitary in one patient evaluated at early childhood, and a borderline hypoplastic gland in the 2 patients evaluated at puberty. We describe a novel missense mutation in the GHRH-R. The high incidence of the mutant allele in Israeli Arabs suggests that the mutation may be a common cause of familial IGHD in this population.

Investigating the role of the growth hormone–insulin-like growth factor (GH–IGF) axis as a determinant of male bone mineral density (BMD)

Introduction The GH–IGF axis has profound effects on bone metabolism and may be important in the etiology of idiopathic osteoporosis. Serum IGF-I is often low in men with osteoporosis, which may be attributable to GH hypo-secretion or hepatic GH insensitivity. We studied the GH–IGF axis in depth to look for evidence to support these hypotheses. Materials and methods 28 healthy 60- to 70-year-old men with low, intermediate, or normal BMD were studied. GH secretion was measured by overnight urine collection. GH reserve was assessed by exercise and glucagon stimulation tests. Hepatic IGF-I production was investigated using a GH–IGF-I generation test. Data were analyzed using Pearson’s correlation coefficient, linear regression, and analysis of variance. Results Serum IGF-I was reduced in subjects with low BMD ( P = 0.009). There was no difference in GH secretion or reserve between the groups. Overall, GH reserve and IGF-I were positively related but this was attenuated in the low BMD group. However, no statistically significant difference in IGF-I generation capacity between BMD groups was found. Conclusions Men with reduced BMD have low IGF-I but normal GH secretion and reserve. Our data suggested, but could not confirm, hepatic resistance to GH as a mechanism for this association.

Final height in short polytransfused thalassemia major patients treated with recombinant growth hormone

We measured the final height (FH) of 25 short polytransfused thalassemia major (Th) patients (18 males) with a reduced GH reserve treated for 3.3 +/- 1.2 yr with recombinant GH (rhGH), 0.2 mg/kg/week sc. At baseline, all patients were clinically prepubertal; their chronological (CA) and bone ages (BA) were 13.6 +/- 2.0 and 11.4 +/- 1.6 yr, respectively. In 9 out of 18 males and 5 out of 7 females, the onset of puberty occurred spontaneously during the treatment. At the end of the rhGH administration, the height of the enrolled children was not significantly increased when calculated for CA (HxCA), while it was significantly decreased (p=0.004) when calculated for BA (HxBA); the BA increase (3.29 +/- 1.65 yr) was significantly higher (p<0.001) than the height age increase (2.16 +/- 0.98 yr). The FHxCA showed a significant increase (p=0.001) compared to both baseline and the end of therapy, while the FHxBA was significantly decreased (p<0.001) compared with the corresponding value at baseline. At the end of therapy, both HxCA and HxBA resulted positively related to the BA at baseline (r=0.50 and 0.42, p=0.012 and 0.034, respectively). FH was positively correlated with CA (r=0.63, p=0.001), BA (r=0.68, p<0.001) and HxBA (r=0.59, p=0.002) evaluated at baseline, and with both HxCA and HxBA (r=0.82 and 0.74, respectively, p<0.001), evaluated at the end of treatment. A negative correlation was found between FH and the length of treatment (r=-0.56, p=0.004). Our data seem to exclude that prolonged rhGH therapy could improve FH in Th patients; on the contrary, a negative effect may be hypothesized.

Prevalence of hypopituitarism and growth hormone deficiency in adults long‐term after severe traumatic brain injury

Traumatic brain injury (TBI) has been associated with hypopituitarism and GH deficiency. However, TBI-mediated hypopituitarism may be more frequent than previously thought. The present work, performed in patients with severe TBI at least 1 year before, had three aims: (i) to evaluate the prevalence of hypopituitarism, (ii) in particular to evaluate the prevalence of GH deficiency, and (iii) to compare three different tests of GH reserve in this cohort. From a nonselected group of 249 patients admitted to our Clinical Centre for severe TBI over the last 5 years, 200 of them answered a custom made questionnaire of symptoms of hypopituitarism enclosed in the invitation letter to participate in the study. A total of 170 (99 men and 14 women), accepted to participate in the study (study cohort); 57 had normal questionnaires and were not further studied, 14 discontinued the study, and 99 attended the hospital for dynamic tests of pituitary hormone deficiencies. From these, 44 subjects with IGF-I in the lower range were tested with GHRH+GHRP-6; ITT; and glucagon tests of GH reserve, on three different occasions. Pituitary hormones plus IGF-I and target gland hormones were analysed. With regard to the initial cohort of 170 subjects (100%), three (1.7%) showed diabetes insipidus; 10 (5.8%) TSH deficiency, 11 (6.4%) ACTH deficiency and 29 (17%) gonadotrophin deficiency. In 10 subjects (5.8%), GH deficiency was diagnosed by strict criteria. Finally, 15 (8.8%) showed combined deficit of several hormones. After severe head trauma, gonadotrophin deficiency was the most common pituitary deficit. GH deficiency showed a prevalence similar to ACTH and TSH deficits, i.e. near 6% of the cohort. Taken together, 24.7% of the subjects studied showed any type of pituitary hormone deficiency.

Evaluation of GH reserve in patients with adrenal incidentalomas and biochemical evidence of subclinical autonomous glucocorticoid hypersecretion

Although it is well established that overt hypercortisolism in patients with active Cushing's syndrome leads to a profound suppression of stimulated GH secretion, the role of subclinical autonomous glucocorticoid hypersecretion (SAGH), currently detected with increasing frequency in patients with adrenal incidentalomas, on GH secretory reserve has received little attention. The aim of the present study was to evaluate whether SAGH in patients presented with adrenal incidentalomas has a negative effect on GH secretory reserve. Sixteen patients with overt Cushing's syndrome (CS) and 36 patients with adrenal incidentalomas were investigated. The latter group was further divided in 23 patients who demonstrated an adequate suppression of cortisol levels (of < 70 nmol/l) following the low-dose dexamethasone suppression test (LDDST) and in 13 patients, who failed to suppress (cortisol levels post-LDDST > 70 nmol/l). The former group was defined as normocortisolaemic (NC) and the latter group as representing patients with SAGH. The combined pyridostigmine + GHRH test (PD + GHRH) was used to assess the GH secretory reserve of these patients. Peak GH levels following PD + GHRH administration were significantly lower in CS patients compared to both the NC and SAGH group of patients with adrenal incidentalomas (2.2 +/- 0.7 vs. 18.9 +/- 2.6 and 21.5 +/- 3.6 microg/l, respectively, P < 0.05); no difference was observed in peak GH responses between the NC and SAGH group of patients. A subnormal GH response (defined as GH(max) < 12.8 microg/l) was observed in all 16 patients with CS. However, only seven NC and three SAGH patients failed to respond adequately. Correlation analysis revealed a negative correlation between peak GH response to PD + GHRH and plasma cortisol concentrations in CS patients (R =-0.6, P = 0.012), while in patients with adrenal incidentalomas such a correlation was absent. Contrary to patients with CS in whom body mass index (BMI) was not correlated to peak GH, a significant negative correlation between peak GH response to PD + GHRH and BMI was disclosed in patients with adrenal incidentalomas (R =-0.49, P = 0.003). In these patients, again contrary to CS patients, a significant negative correlation was also found between peak GH post PD + GHRH and age (R = -0.46, P = 0.002). In conclusion, our results provide evidence that, contrary to patients with overt CS, SAGH does not affect the GH secretory response to provocative stimulation.

Anterior pituitary dysfunction in survivors of traumatic brain injury.

Recent data suggest that anterior pituitary dysfunction after traumatic brain injury (TBI) is common. We sought to confirm the results of earlier studies in a larger cohort of patients with dynamic testing of pituitary function. We studied 102 consecutive TBI survivors (85 males; median age 28, range 15-65 yr) who had survived severe or moderate TBI (initial Glasgow Coma Scale score 3-13) at a median of 17 months (range 6-36) post event. GH and ACTH reserves were initially assessed using the glucagon stimulation test (GST). Normative data on GH and cortisol responses to the GST were obtained from 31 matched healthy controls. Patients with subnormal GH or cortisol responses were further evaluated, using the insulin tolerance test (ITT) or arginine + GHRH test for GH assessment and the ITT or 250-microg short synacthen test for the assessment of ACTH reserve. Patients were considered to be GH or ACTH deficient if they failed both the GST and the second provocative test. Baseline thyroid function, prolactin, IGF-I, gonadotropins, testosterone, or estradiol was performed in all patients and compared with local reference ranges.In controls, normal response to the GST was a stimulated GH peak of greater than 5 microg/liter and cortisol peak greater than 450 nmol/liter (16 microg/dl). Eighteen TBI patients (17.6%) had GH response to the GST less than 5 microg/liter, 11 of whom also failed the ITT or the arginine + GHRH tests. GH-deficient patients had significantly higher body mass index (P = 0.003), and lower IGF-I concentrations (P < 0.001), than GH-sufficient patients. Twenty-three patients (22.5%) had cortisol responses to GST less than 450 nmol/liter, 13 of whom also failed the ITT or short synacthen test. GH or ACTH deficiencies were not related to age, Glasgow Coma Scale score, or the presence of other pituitary hormone abnormalities (P > 0.05). Twelve patients (11.8%) had gonadotropin and one (1%) had thyrotrophin deficiencies. Twelve patients (11.8%) had hyperprolactinemia. Twenty-nine patients (28.4%) had at least one anterior pituitary hormone deficiency. This is the largest study, to date, of hypopituitarism after TBI and confirms a high prevalence of undiagnosed anterior pituitary hormone abnormalities in survivors of TBI. Hypopituitarism is a treatable cause of morbidity after TBI. In addition to conventional pituitary hormone replacement, the potential of GH treatment to enhance recovery needs to be examined in a prospective study.

Assessment of GH reserve before and after successful treatment of adult patients with Cushing's syndrome.

Several studies have demonstrated impaired GH secretion in patients with active Cushing's syndrome (CS). It has been suggested that persistence of GH deficiency, despite treatment of cortisol excess, may delay the recovery of these patients and therefore temporary treatment with GH may have some benefit. However, the time course of restoration of GH secretion after successful treatment of CS has only been investigated in a limited number of mostly paediatric reports. The aim of the present study was the evaluation of GH reserve in adult patients with CS before and after correction of cortisol excess. Sixteen patients (12 females, four males) with CS aged 44.7 +/- 5.05 years were recruited. These included seven patients with Cushing's disease, four patients with ectopic ACTH secretion and five patients with adrenal adenoma. All patients were evaluated before any therapeutic intervention. Twelve patients were successfully treated following appropriate surgery and these were further studied. The combined pyridostigmine/GHRH test was used to assess GH reserve in these patients. In a proportion of cases an insulin tolerance test (ITT) was also used. Before any therapeutic intervention, an impaired GH response to PD/GHRH was noted in all patients. Restoration of GH response at 6 months was observed in six patients (50%); at 12 months in two; at 18 months in one patient. Two of the patients with no restoration of GH response at 12 months did not accept further investigation. Only one patient did not achieve an adequate GH response even when tested 30 months following cure of CS. Restoration of GH reserve was more commonly observed in those patients in whom there was recovery of the HPA axis. There was a good correlation between peak GH levels to PD + GHRH and ITT. No statistically significant difference was revealed in IGF-I levels between pre- and post-treatment evaluation. Adult patients with active Cushing's syndrome demonstrate a profound suppression of stimulated GH secretion. In the majority of these patients the disruption of GH secretion is normalized within a year after successful treatment of endogenous cortisol excess.

Growth Hormone Secretagogues as Diagnostic Tools in Disease States

One of the most active topics in the growth hormone-IGF-1 field is that of the so-called growth hormone secretagogues (GHS). At a time when the isolation of GHRH had not occurred, the GHS were developed as artificial tools to release GH. The interest in these groups of compounds was rekindled when it was realized that they were not surrogates of GHRH nor were they acting through the modulation of the release of either GHRH or somatostatin. With the subsequent cloning of the specific receptor of GHS, and today of the natural ligand for that receptor, named ghrelin, it soon become clear that GHS and the GHS-receptor were part of a new physiological system involved in GH regulation. The dual control of GH secretion became a trinity. GHS releases GH when administered by any route--oral, iv, sc, and even transdermally-with a surprising potency and reproductivity. In addition, GHS when administered together with GHRH exert a synergistic action on GH secretion and that combined administration is the most potent GH releaser to date. Clinical studies have demonstrated that the GHS-GHRH administration may be considered the new "gold standard" test of GH reserve in humans, as the GH secretion so elicited is not altered by gender, adiposity, or age. The combined administration of GHRH plus GHS is able to discriminate between healthy subjects and patients with adult GH deficiency, suggesting a considerable utility in the clinical setting.

The diagnosis of growth hormone deficiency (GHD) in successfully treated acromegalic patients

Due to persistent qualitative abnormalities in GH secretion following treatment, and lack of a sensitive marker of GHD in mid-adult life it is extremely difficult to diagnose GHD in treated acromegalic patients. The diagnosis of GHD in patients with pituitary disease relies on provocative tests of GH reserve. Arginine releases GH by reducing somatostatin inhibition of GH release, whereas GH secretagogues (GHS) affect GH release by direct stimulation of the GHS receptor, though an intact GH releasing hormone (GHRH) axis is a prerequisite. The peak GH response to insulin-induced hypoglycaemia and arginine in acromegalic patients, in whom basal serum GH levels of less than 5 mU/l have been achieved, is greatly diminished in those treated by hypothalamo-pituitary irradiation. We aimed to study the response of successfully treated acromegalic patients to the growth hormone secretagogue hexarelin in view of its different putative mechanism of action, and in addition, to determine whether it has any value in the diagnosis of GH deficiency in this subset of patients. Nineteen acromegalic patients, in whom mean serum GH levels below 5 mU/l have been achieved through treatment, were recruited. Eight of the patients had been treated by surgery alone (Group A) and 11 had received primary or postoperative irradiation (Group B). All patients underwent 20 min blood sampling to provide a 24-h GH profile. Serum IGF-I was measured from a sample drawn between 0900 h and 1000 h. On a second visit arginine 20 g/m2 was infused over 30 min, blood samples were taken before commencing the infusion and at 30-min intervals thereafter for 180 min. At the final visit hexarelin 1.5 mcg/kg was administered as an intravenous bolus at t = 0. Blood was drawn at 15-min intervals from - 30 to 180 min. All patients in group A showed an increment in serum GH following hexarelin (DeltaGHHEX) > 20 mU/l, a normal response to arginine, and a mean 24-h GH > 0.5 mU/l. In group B only 4/11 achieved a DeltaGHHEX > 20 mU/l, 5/11 producing a response of < 2 mU/l. Four of the five patients with a DeltaGHHEX < 2 mU/l were also demonstrated to have a mean 24-h GH of < 0.5 mU/l and serum IGF-I SDS < + 0.5. All four patients in Group B who achieved a DeltaGHHEX > 20 mU/l, were observed to show an absent or minimal GH response to arginine. Despite loss of the GH response to arginine, the DeltaGHHEX is retained in a proportion of those patients in whom "safe" GH levels were achieved following irradiation. From the putative mechanisms of action of these provocative agents a plausible explanation would be that the GHRH axis is more resilient than endogenous somatostatin-secreting neurones to radiation-induced damage. Furthermore, GH secretagogues may have a role, in combination with serum IGF-I levels, in the diagnosis of GH deficiency in treated acromegaly.

Mechanisms of reduced body growth in the pubertal feminized male rat: unbalanced estrogen and androgen action on the somatotropic axis.

It is well known that the sex difference in body growth at puberty is modulated by a complex interplay between sex steroids and somatotropic axis; however, the exact role played by sex steroids remains a matter of controversy. The aim of this study was to assess the mechanisms by which sex steroids regulate body growth during pubertal development. Flutamide, a non-steroid-blocking androgen receptor, was subcutaneously administered to 30-d-old male Wistar rats for 4 wk. The blockade of the androgen receptor led to a marked elevation in serum testosterone and an increment in serum estradiol. Flutamide administration decreased body weight gain, serum IGF-I levels, hepatic IGF-I mRNA, and GH receptor mRNA content. There were no significant changes in serum GH concentration, pituitary GH reserve, and pituitary GH mRNA content. Flutamide lowered hypothalamic somatostatin mRNA content and augmented hypothalamic immunoreactive somatostatin stores, but did not alter hypothalamic immunoreactive GH-releasing factor stores. Our findings indicate that during pubertal development of the male rat, the imbalance between androgen and estrogen actions determines an abnormal somatic growth, which is at least partly exerted through the peripheral or hepatic modification of the somatotropic axis that occurs under the high or exclusive action of estrogens. Potential implication of coincident sex-specific regulated mode of pulsatile GH secretion cannot be excluded from this random serum GH sample study.