Changing patterns of the adult growth hormone deficiency diagnosis documented in a decade-long global surveillance database

Unusual and lesser-known rare causes of adult growth hormone deficiency

Growth hormone is among the most common hormones to be deficient in pituitary insult. It can occur either in isolation or combined with other hormone deficiencies. Growth hormone deficiency in adults (AGHD) can be due to causes acquired in adulthood or have a childhood-onset etiology, but the former is about three times more common. Usual causes of AGHD include mass effects due to a pituitary tumour, and/or its treatment (surgery, medical therapy, or radiotherapy), or radiotherapy to the head and neck region for non-pituitary lesions. The unusual or lesser-known causes of AGHD, are usually due to non-tumoral etiology and range from vascular and infective to inflammatory and miscellaneous causes. These not only expand the spectrum of AGHD but may also contribute to increased morbidity, adverse metabolic consequences, and mortality due to the primary condition, if unrecognised. The review features these lesser-known and rare causes of AGHD and highlights their clinical and diagnostic implications.

Long-Term Safety of Growth Hormone Deficiency Treatment in Cancer and Sellar Tumors Adult Survivors: Is There a Role of GH Therapy on the Neoplastic Risk?

Experimental studies support the hypothesis that GH/IGF-1 status may influence neoplastic tissue growth. Epidemiological studies suggest a link between GH/IGF-1 status and cancer risk. However, several studies regarding GH replacement safety in childhood cancer survivors do not show a prevalence excess of de novo cancers, and several reports on children and adults treated with GH have not shown an increase in observed cancer risk in these patients. The aim of this review is to provide an at-a-glance overview and the state of the art of long-term effects of GH replacement on neoplastic risk in adults with growth hormone deficiency who have survived cancer and sellar tumors.

Long-term Safety of Growth Hormone in Adults With Growth Hormone Deficiency: Overview of 15 809 GH-Treated Patients

CONTEXT

Data on long-term safety of growth hormone (GH) replacement in adults with GH deficiency (GHD) are needed.

OBJECTIVE

We aimed to evaluate the safety of GH in the full KIMS (Pfizer International Metabolic Database) cohort.

METHODS

The worldwide, observational KIMS study included adults and adolescents with confirmed GHD. Patients were treated with GH (Genotropin [somatropin]; Pfizer, NY) and followed through routine clinical practice. Adverse events (AEs) and clinical characteristics (eg, lipid profile, glucose) were collected.

RESULTS

A cohort of 15 809 GH-treated patients were analyzed (mean follow-up of 5.3 years). AEs were reported in 51.2% of patients (treatment-related in 18.8%). Crude AE rate was higher in patients who were older, had GHD due to pituitary/hypothalamic tumors, or adult-onset GHD. AE rate analysis adjusted for age, gender, etiology, and follow-up time showed no correlation with GH dose. A total of 606 deaths (3.8%) were reported (146 by neoplasms, 71 by cardiac/vascular disorders, 48 by cerebrovascular disorders). Overall, de novo cancer incidence was comparable to that in the general population (standard incidence ratio 0.92; 95% CI, 0.83-1.01). De novo cancer risk was significantly lower in patients with idiopathic/congenital GHD (0.64; 0.43-0.91), but similar in those with pituitary/hypothalamic tumors or other etiologies versus the general population. Neither adult-onset nor childhood-onset GHD was associated with increased de novo cancer risks. Neutral effects were observed in lipids/fasting blood glucose levels.

CONCLUSION

These final KIMS cohort data support the safety of long-term GH replacement in adults with GHD as prescribed in routine clinical practice.

Effects of adult growth hormone deficiency and replacement therapy on the cardiometabolic risk profile

Adult growth hormone deficiency (AGHD) is considered a rare endocrine disorder involving patients with childhood-onset and adult-onset growth hormone deficiency (AoGHD) and characterized by adverse cardiometabolic risk profile. Besides traditional cardiovascular risk factors, endothelial dysfunction, low-grade inflammation, impaired adipokine profile, oxidative stress and hypovitaminosis D may also contribute to the development of premature atherosclerosis and higher cardiovascular risk in patients with AGHD. Growth hormone replacement has been proved to exert beneficial effects on several cardiovascular risk factors, but it is also apparent that hormone substitution in itself does not eliminate all cardiometabolic abnormalities associated with the disease. Novel biomarkers and diagnostic techniques discussed in this review may help to evaluate individual cardiovascular risk and identify patients with adverse cardiometabolic risk profile. In the absence of disease-specific guidelines detailing how to assess the cardiovascular status of these patients, we generally recommend close follow-up of the cardiovascular status as well as low threshold for a more detailed evaluation.

Somatropin therapy in italian adults with growth hormone deficiency

BACKGROUND

In adult population, Growth Hormone Deficiency (GHD) is a complex clinical condition with heterogeneity of causes and duration. Growth Hormone (GH) replacement therapy has beneficial effects entailing a chronic and expensive use. Therefore, entity, appropriateness and standardization of GHD treatment need to be accurately analysed. In Italy, the epidemiological surveillance on somatropin therapy is entrusted to the National Register of Growth Hormone Therapy (Registro Nazionale degli Assuntori dell'Ormone della Crescita-RNAOC) by the Italian Regulation, in accordance of which the RNAOC-database is collecting the notifications of somatropin prescriptions.

METHODS

Aim of this study is to analyse data on somatropin-treated adult population communicated to the RNAOC by the specialist centres of 15 Italian regions and 2 autonomous provinces.

RESULTS

From 2011 to 2019, the somatropin-treated adults were 970 with 4061 examinations (1.21 ± 0.33 visits/year). The diagnoses were: hypopituitarism (n = 579); hypophysectomy (n = 383); and congenital GHD (n = 3). Five subjects were addressed with diagnoses not included in the regulation. The starting posology of somatropin was 0.320 (± 0.212) mg/day, 0.292 (± 0.167) mg/day in male and 0.360 (± 0.258) in female patients, with 7 administrations/week in 70.31% of the prescriptions. The differences in posology by gender persisted at 10th year of the follow-up. Starting dosage was higher in patients diagnosed with adult GHD before the age of 30 (0.420 ± 0.225 mg/day), with a progressive decrease of the dosage during the follow-up.

CONCLUSIONS

This is the first report on adult GH treatment, describing numbers, diagnoses, and pharmaceutical prescriptions associated to somatropin therapy in a large cohort of Italian GHD-adults.

Safety of growth hormone (GH) treatment in GH deficient children and adults treated for cancer and non-malignant intracranial tumors-a review of research and clinical practice

Individuals surviving cancer and brain tumors may experience growth hormone (GH) deficiency as a result of tumor growth, surgical resection and/or radiotherapy involving the hypothalamic-pituitary region. Given the pro-mitogenic and anti-apoptotic properties of GH and insulin-like growth factor-I, the safety of GH replacement in this population has raised hypothetical safety concerns that have been debated for decades. Data from multicenter studies with extended follow-up have generally not found significant associations between GH replacement and cancer recurrence or mortality from cancer among childhood cancer survivors. Potential associations with secondary neoplasms, especially solid tumors, have been reported, although this risk appears to decline with longer follow-up. Data from survivors of pediatric or adult cancers who are treated with GH during adulthood are scarce, and the risk versus benefit profile of GH replacement of this population remains unclear. Studies pertaining to the safety of GH replacement in individuals treated for nonmalignant brain tumors, including craniopharyngioma and non-functioning pituitary adenoma, have generally been reassuring with regards to the risk of tumor recurrence. The present review offers a summary of the most current medical literature regarding GH treatment of patients who have survived cancer and brain tumors, with the emphasis on areas where active research is required and where consensus on clinical practice is lacking.

Contribution of Ghrelin to the Pathogenesis of Growth Hormone Deficiency

In this review we described the interactions between ghrelin and the growth hormone (GH)-insulin-like growth factor 1 (IGF-1) axis in children and adults with growth hormone deficiency (GHD). A possible involvement of these interactions in the pathogenesis of unexplained cases of GHD was suggested. Current research provides more and more details to the knowledge on the circadian rhythm of ghrelin. We gathered reports on the decreasing effect of Helicobacter pylori-related chronic gastritis on the number of ghrelin immunopositive cells and the consequent decrease in ghrelin serum concentration. The gastrointestinal tract microflora modification of the ghrelin action, by the mechanism of molecular mimicry, was also stressed. Moreover, the mutual relationships between ghrelin and the TSH-FT4/FT3 axis in growth and metabolic processes are described. It is to be recalled that FT4 and FT3 exert a permissive impact on IGF-1 action and, in turn, GH, in reaction mediated by IGF-1, enhances the monodeiodination of FT4 to FT3. Finally, we discussed the latest attempts to use the GH secretagogue receptor (GHS-R) analogues for possible diagnostic and therapeutic purposes.

Effect of recombinant human growth hormone on liver fat content in young adults with nonalcoholic fatty liver disease

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is highly prevalent in young adults with obesity. Obesity is associated with relative growth hormone (GH) deficiency, and data from animal studies and from humans with pituitary GH deficiency suggest a role for GH deficiency in the pathogenesis of NAFLD. The effects of GH on NAFLD in those with obesity are unknown, however, prompting this pilot study to assess effects of GH administration on measures of NAFLD in young adults.

METHODS

Twenty-four men and women aged 18-29 years with BMI ≥ 30 kg/m² , hepatic fat fraction (HFF) ≥ 5% on proton magnetic resonance spectroscopy (¹ H-MRS) and insulin-like growth factor 1 (IGF-1) z-score ≤ 0 were randomized to treatment with recombinant human GH (rhGH) versus no treatment for 24 weeks. The primary endpoint was change in HFF.

RESULTS

Compared to no treatment, the effect size of rhGH on absolute HFF over 24 weeks was -3.3% (95% confidence interval: -7.8%, 1.2%; p = .14). At 24 weeks, HFF < 5% was achieved in 5 of 9 individuals receiving rhGH versus 1 of 9 individuals receiving no treatment (p = .04). rhGH did not significantly reduce ALT, AST or GGT. Serum IGF-1 increased as expected with rhGH treatment, and there were no changes in fasting lipids, C-reactive protein, fasting glucose or 2-h glucose following an oral glucose tolerance test.

CONCLUSION

Data from this pilot study suggest that rhGH treatment in young adults with obesity and NAFLD may have benefits to reduce liver fat content, although larger studies are needed to confirm this effect.

Immune dyscrasia in adult growth hormone deficiency: Evaluation of hemolytic complement activity (CH50) and IgG subclasses

CH50 is a screening assay for the activation of the classical complement pathway, the immunoglobulins-mediated one, activated in several inflammatory diseases. Adult growth hormone deficiency (aGHD) is recognized as a chronic inflammatory condition, although poorly evaluated under the profile of inflammatory biomarkers. The aim of this case-control observational study is to analyze CH50 and immunoglobulins G (IgG) subclasses production in aGHD, comparing this condition to healthy controls. 38 subjects were included and divided as follows: aGHD (n = 18, 6 females and 12 males); healthy controls (n = 20, 10 females and 10 males). GHD was diagnosed with dynamic test using Growth Hormone-Releasing Hormone (GHRH 50 μg i.v. + arginine 0,5 g/Kg), with a peak GH response < 9 μg/L when BMI was <30 kg/m² or < 4 μg/L when BMI was >30 kg/m². The two groups were evaluated for hormonal and metabolic parameters, CH50 and IgG subtypes. IgG1 and IgG2 were significantly higher in controls than in aGHD, while IgG3 and IgG4 showed a trend to higher levels in controls, although not significant. Furthermore, CH50 levels were significantly higher in aGHD. These data substantiate the hypothesis of a dyscrasia in IgG subclasses production in aGHD. As IgG levels decrease, CH50 levels do not.

Growth Hormone Therapy Does Not Increase the Risk of Craniopharyngioma and Nonfunctioning Pituitary Adenoma Recurrence

CONTEXT

Recombinant human growth hormone (rhGH) replacement therapy is often prescribed in patients with nonfunctioning pituitary adenoma (NFPA) or craniopharyngioma.

OBJECTIVE

To study whether rhGH therapy in patients with adult growth hormone deficiency (AGHD) increases the risk of pituitary tumor recurrence.

DESIGN

Retrospective, observational study.

SETTING

Tertiary care center.

PATIENTS

We studied 283 consecutive patients with AGHD due to NFPA or craniopharyngioma between 1995 and 2018.

INTERVENTION

rhGH treatment at standard doses was initiated in 123 patients (43.5%). The remaining 160 patients served as controls.

MAIN OUTCOME MEASURE

Risk of tumor recurrence in rhGH-treated and control patients.

RESULTS

In univariate analysis, recurrence of the pituitary tumor was less frequent in rhGH-treated patients (19.5%) than in controls (29.7%; hazard ratio [HR] 0.53, 95% confidence interval [CI] 0.32-0.86; P = .01). Multivariate Cox analysis demonstrated that the risk of tumor recurrence was associated with detection of residual disease at the baseline magnetic resonance imaging (HR 9.17; 95% CI, 4.88-17.22; P < .001) and not having performed radiotherapy (HR 16.97; 95% CI, 7.55-38.16; P < .001), while rhGH treatment was no longer associated with a lower risk of recurrence (HR 0.82; 95% CI, 0.47-1.44; P = .50).

CONCLUSIONS

We found no association between rhGH replacement and the risk of tumor recurrence in patients with AGHD caused by NFPA or craniopharyngioma. These data add to the mounting evidence that rhGH therapy has a neutral effect on the recurrence of pituitary tumors.

PRÉCIS

Replacement therapy with rhGH is prescribed to patients with adult growth hormone deficiency. Our study found no increased risk of pituitary tumor recurrence.

Growth hormone replacement in adults: Real-world data from two large studies in US and Europe

OBJECTIVE

This report describes the effectiveness and safety of growth hormone replacement in 3180 adult patients with growth hormone deficiency followed-up for 0.0-12.2 years in two completed, complementary, non-interventional, multicentre studies, NordiNet® International Outcome Study (IOS) (NCT00960128) and the American Norditropin® Studies: Web-Enabled Research (ANSWER) Program (NCT01009905).

DESIGN

In both studies, Norditropin® (somatropin; Novo Nordisk A/S, Denmark) was administered at the discretion of the treating physician and according to routine practice. We present data on baseline characteristics, growth hormone dose, safety data and change from baseline in waist circumference, body mass index and bioimpedance (NordiNet® IOS only).

RESULTS

Mean (SD) baseline characteristics (effectiveness analysis set) in NordiNet® IOS (n = 971) and ANSWER (n = 304): females, 45%; 69%; mean growth hormone dose (mg/day) (female, 0.338 [0.177]; male, 0.289 [0.157]); (female, 0.501 [0.313]; male, 0.505 [0.351]). Most patients had BMI ≥25 kg/m². Median (P10,P90) exposure (females, 3.5 [0.42,11.0]; 1.6 [3.2; 0.3,8.6]; males, 4.1 [0.33,10.8]; 2.3 [2.9; 0.0,7.5] years). Mean (SD) change from baseline for waist circumference (-0.46 [6.38] cm [n = 403], BMI (0.30 [3.30] kg/m² [n = 857]) and bioimpedance (-17.4 (59.19) ohm [n = 239]) were associated with growth hormone dose (waist/bioimpedance) and duration of follow-up (BMI/bioimpedance). No new safety signals were observed among patients in the full analysis set (NordiNet® IOS, n = 2321; ANSWER, n = 859).

CONCLUSIONS

Long-term growth hormone replacement is associated with an improvement in body composition. The accumulated data from >10 years of follow-up support the long-term effectiveness and safety of growth hormone replacement as prescribed in clinical practice.

Analysis of characteristics and outcomes by growth hormone treatment duration in adult patients in the Italian cohort of the Hypopituitary Control and Complications Study (HypoCCS)

PURPOSE

To examine differences in effects according to growth hormone (GH) treatment duration in adult GH-deficient patients.

METHODS

In the Italian cohort of the observational Hypopituitary Control and Complications Study, GH-treated adults with GH deficiency (GHD) were grouped by duration of treatment; ≤ 2 years (n = 451), > 2 to ≤ 6 years (n = 387) and > 6 years (n = 395). Between-group differences in demographics, medical history, physical characteristics, insulin-like growth factor-I standard deviation score (IGF-I SDS) and lipid profile at baseline, last study visit and changes from baseline to last study visit were assessed overall, for adult- and childhood-onset GHD and by gender using ANOVA for continuous variables and Chi-squared test for categorical variables.

RESULTS

At baseline, treatment duration groups did not differ significantly for age, gender, body mass index, GHD onset, IGF-I SDS, lipid profile, and quality of life. Mean initial GH dose did not differ significantly according to treatment duration group in any subgroup, except female patients, with highest mean dose seen in the longest duration group. In the longest duration group for patients overall, adult-onset patients and male patients, there were significant decreases in GH dose from baseline to last visit, and in total and low-density lipoprotein (LDL)-cholesterol concentrations. IGF-I SDS increased, to a greater extent, in the longest duration group for patients overall and female patients.

CONCLUSIONS

The results show that long-term GH treatment is associated with decreasing GH dose, increased IGF-I, decreased LDL-cholesterol and the presence of surrogate markers that help to give confidence in a diagnosis of GHD.

Etiology of Hypopituitarism in Adult Patients: The Experience of a Single Center Database in the Serbian Population

There are only a few published studies related to the population-based etiology of hypopituitarism. New risks for developing hypopituitarism have been recognized in the last 10 years. Aim. To present data regarding the etiology of hypopituitarism collected in a tertiary center over the last decade. This is a cross-sectional database study. Patients and Methods. We included 512 patients (pts) with hypopituitarism, with a mean age of 45.9 ± 1.7 yrs (range: 18-82; male: 57.9%). Results. Nonfunctional pituitary adenomas were presented in 205 pts (40.5%), congenital causes in 74 pts (14.6%), while acromegaly and prolactinomas were presented in 37 (7.2%) and 36 (7.0%) patients, respectively. Craniopharyngiomas were detected in 30 pts (5.9%), and head trauma due to trauma brain injury-TBI and subarachnoid hemorrhage-SAH in 27 pts (5.4%). Survivors of hemorrhagic fever with renal syndrome (HFRS) and those with previous cranial irradiation were presented in the same frequency (18 pts, 3.5% each). Conclusion. The most common causes of hypopituitarism in our database are pituitary adenomas. Increased awareness of the other causes of pituitary dysfunction, such as congenital, head trauma, extrapituitary cranial irradiation, and infections, is the reason for a higher frequency of these etiologies of hypopituitarism in the presented database.

Characteristics and outcomes of Italian patients from the observational, multicentre, hypopituitary control and complications study (HypoCCS) according to tertiles of growth hormone peak concentration following stimulation testing at study entry

OBJECTIVE

To determine whether characteristics and outcomes of Italian patients in the observational global Hypopituitary Control and Complication Study (HypoCCS) differed according to the degree of GH deficiency (GHD).

DESIGN

Patients were grouped by tertiles of stimulated GH peak concentration at baseline (Group A lowest tertile, n = 342; Group B middle tertile, n = 345; Group C highest tertile, n = 338).

RESULTS

Baseline demographics, lipid levels, body mass index categories and mean Framingham cardiovascular risk indexes were similar in the three groups and remained substantially unchanged over time, with no subsequent significant between-group differences (except mean levels of triglycerides increased in the highest tertile group). GHD was adult-onset for >75% of patients in all groups. The percentage of patients with multiple pituitary deficiencies was higher in Group A than in the other groups; isolated GHD was reported with highest frequency in Group C. Patients in Group A received the lowest mean starting dose of GH. Hyperlipidaemia at baseline was reported in 35·1%, 31·1% and 24·7% of patients in groups A, B and C, respectively (P = 0·029). Mean duration of GH treatment was 7·21, 5·45 and 4·96 years, respectively. The proportion of patients with adverse events did not differ significantly between groups, with a low prevalence over time of diabetes and cancer.

CONCLUSIONS

In Italian patients from HypoCCS, the level of GH deficit did not influence changes over time in metabolic parameters or adverse event profile, despite differences in GHD severity at baseline and in the starting GH dose.

Incidence of primary cancers and intracranial tumour recurrences in GH-treated and untreated adult hypopituitary patients: analyses from the Hypopituitary Control and Complications Study

OBJECTIVE

Speculation remains that GH treatment is associated with increased neoplasia risk. Studies in GH-treated childhood cancer survivors suggested higher rates of second neoplasms, while cancer risk data for GH-treated and untreated hypopituitary adults have been variable. We present primary cancer risk data from the Hypopituitary Control and Complications Study (HypoCCS) with a focus on specific cancers, and assessment of recurrence rates for pituitary adenomas (PA) and craniopharyngiomas (CP).

DESIGN

Incident neoplasms during HypoCCS were evaluated in 8418 GH-treated vs 1268 untreated patients for primary malignancies, 3668 GH-treated vs 720 untreated patients with PA history, and 956 GH-treated vs 102 untreated patients with CP history.

METHODS

Using population cancer rates, standardised incidence ratios (SIRs) were calculated for all primary cancers, breast, prostate, and colorectal cancers. Neoplasm rates in GH-treated vs untreated patients were analysed after propensity score adjustment of baseline treatment group imbalances.

RESULTS

During mean follow-up of 4.8 years, 225 primary cancers were identified in GH-treated patients, with SIR of 0.82 (95% CI 0.71-0.93). SIRs (95% CI) for GH-treated patients were 0.59 (0.36-0.90) for breast, 0.80 (0.57-1.10) for prostate, and 0.62 (0.38-0.96) for colorectal cancers. Cancer risk was not statistically different between GH-treated and untreated patients (relative risk (RR)=1.00 (95% CI 0.70-1.41), P=0.98). Adjusted RR for recurrence was 0.91 (0.68-1.22), P=0.53 for PA and 1.32 (0.53-3.31), P=0.55 for CP.

CONCLUSIONS

There was no increased risk for all-site cancers: breast, prostate or colorectal primary cancers in GH-treated patients during HypoCCS. GH treatment did not increase the risk of PA and CP recurrences.

Fracture risk in adult patients treated with growth hormone replacement therapy for growth hormone deficiency: a prospective observational cohort study

BACKGROUND

To our knowledge, no controlled studies of the effects of long-term growth hormone replacement on fracture risk in adult patients with growth hormone deficiency exist. We assessed the effect of growth hormone treatment on fracture risk in patients with growth hormone deficiency from the international Hypopituitary Control and Complications Study (HypoCCS) surveillance database.

METHODS

In this prospective cohort study, patients with growth hormone deficiency were analysed from the HypoCCS database of adults with hypopituitarism from the USA, Canada, Japan, and 14 European countries. Patients were eligible if they were aged 18 years or older and had an established diagnosis of growth hormone deficiency, either alone or with multiple pituitary hormone deficiencies, as identified by clinical history and biochemical testing. Patients were assessed over a mean follow-up period of 4·6 years (SD 3·8). The effect of growth hormone treatment on fracture risk was assessed by Cox proportional hazard modelling with adjustment for several confounders.

FINDINGS

Between Jan 3, 1996, and Dec 15, 2012, we enrolled 10,673 patients to this study. Of the enrolled patients, 1032 patients were excluded from assessment because of incomplete data, leaving 9641 in the analysis cohort. Of these patients, 8374 of received growth hormone and 1267 did not. Annual fracture incidence rate was lower in patients who received growth hormone than in those who did not (fracture incidence rate 1·19% vs 1·91%, hazard ratio [HR] 0·69, 95% CI 0·54-0·88). However, no difference in fracture risk was observed between patients who did and did not receive growth hormone treatment in the subgroup of patients with pre-existing osteoporosis (n=826; 0·97, 0·48-1·95).

INTERPRETATION

Our results suggest that growth hormone replacement therapy could be protective against fracture for adult patients with growth hormone deficiency without previously reported osteoporosis. Starting growth hormone therapy before the onset of osteoporosis might be optimum for bone health of adult patients with growth hormone deficiency.

FUNDING

Eli Lilly and Co.

Hypopituitarism: growth hormone and corticotropin deficiency

This article presents an overview of adult growth hormone deficiency (AGHD) and corticotropin deficiency (central adrenal failure, CAI). Both conditions can result from various ailments affecting the hypothalamus or pituitary gland (most frequently a tumor in the area or its treatment). Clinical manifestations are subtle in AGHD but potentially life-threatening in CAI. The diagnosis needs dynamic testing in most cases. Treatment of AGHD is recommended in patients with documented severe deficiency, and treatment of CAI is mandatory in all cases. Despite significant progress in replacement hormonal therapy, more physiologic treatments and more reliable indicators of treatment adequacy are still needed.

Adult mortality or morbidity is not increased in childhood-onset growth hormone deficient patients who received pediatric GH treatment: an analysis of the Hypopituitary Control and Complications Study (HypoCCS)

BACKGROUND

The French Safety and Appropriateness of Growth Hormone treatments in Europe (SAGhE) cohort has raised concern of increased mortality risk during follow-up into adulthood in certain patients who had received growth hormone (GH) treatment during childhood. The Hypopituitary Control and Complications Study monitored mortality and morbidity of adult GH-deficient patients including those with childhood-onset GH deficiency (COGHD) who received GH treatment as children.

PURPOSE

Evaluate risk of mortality, cancer, myocardial infarction (MI) and stroke in a prospective observational study.

METHODS

COGHD patients [n = 1,204, including 389 diagnosed with idiopathic COGHD (ICOGHD)] had received pediatric GH treatment. Standardized mortality ratios (SMRs), and cancer standardized incidence ratios (SIRs) in patients without a prior cancer were estimated relative to reference populations. Crude incidence rates were estimated for MI and stroke.

RESULTS

No increased mortality or cancer incidence was observed, as compared with reference populations, during a follow-up of 3.7 ± 3.3 years (mean ± SD). The overall SMR for COGHD was 1.14 [95 % confidence interval (CI) 0.55-2.10], and for ICOGHD, 0.33 (0.01-1.84). The overall cancer SIR for COGHD was 0.27 (0.01-1.50), and for ICOGHD, 0.00 (0.00-2.45). No incident case of MI was reported. The crude stroke incidence rate [181.3 per 100,000 person-years] in COGHD patients was consistent with the rates reported in reference populations. No incident case of stroke was identified in ICOGHD patients who are presumed to have no increased stroke risk factors.

CONCLUSIONS

The results indicate no increased risk of mortality or incidence of cancer, stroke, or MI in adult GH-deficient patients who had previously received pediatric GH treatment.

Growth hormone and cancer: an update on progress

PURPOSE OF REVIEW

Animals born with a deficiency in the cell surface receptor for growth hormone (GH) have a significantly reduced risk of developing cancer. Conversely, increased expression levels of GH and the GH receptor (GHR) are detectable in a variety of different human cancers. Here we discuss recent literature contributing to our understanding of the field.

RECENT FINDINGS

In addition to animal evidence, studies of individuals with Laron syndrome suggest that congenital GHR deficiency may also protect humans against cancer. GH expression in certain malignancies is correlated with clinicohistopathological parameters and may contribute the therapeutic resistance. Other recent studies have identified novel aspects of the GH signal transduction pathway, including receptor crosstalk and the involvement of microRNA in endocrine regulation of GH.

SUMMARY

Substantial evidence suggests the GH/insulin-like growth factor-1 axis initiates and promotes progression of cancer. However, important questions remain unanswered regarding the therapeutic utility of GH or GHR antagonism in cancer. Further clinical studies regarding the clinical association of GH expression with human malignancies and translational studies investigating GHR antagonism in animal models of human cancer are critical.

Idiopathic adult growth hormone deficiency

GH secretion is controlled by hypothalamic as well as intrapituitary and peripheral signals, all of which converge upon the somatotroph, resulting in integrated GH synthesis and secretion. Enabling an accurate diagnosis of idiopathic adult GH deficiency (IAGHD) is challenged by the pulsatility of GH secretion, provocative test result variability, and suboptimal GH assay standardization. The spectrum between attenuated GH secretion associated with the normal aging process and with obesity and truly well-defined IAGHD is not distinct and may mislead the diagnosis. Adult-onset GHD is mainly caused by an acquired pituitary deficiency, commonly including prior head/neck irradiation, or an expanding pituitary mass causing functional somatotroph compression. To what extent rare cryptic causes account for those patients seemingly classified as IAGHD is unclear. About 15% of patients with adult GHD and receiving GH replacement in open-label surveillance studies are reported as being due to an idiopathic cause. These patients may also reflect a pool of subjects with an as yet to be determined occult defect, or those with unclear or incomplete medical histories (including forgotten past sports head injury or motor vehicle accident). Therefore, submaximal diagnostic evaluation likely leads to an inadvertent diagnosis of IAGHD. In these latter cases, adherence to rigorous biochemical diagnostic criteria and etiology exclusion may result in reclassification of a subset of these patients to a distinct known acquired etiology, or as GH-replete. Accordingly, rigorously verified IAGHD likely comprises less than 10% of adult GHD patients, an already rare disorder. Regardless of etiology, patients with adult GHD, including those with IAGHD, exhibit a well-defined clinical phenotype including increased fat mass, loss of lean muscle mass, decreased bone mass, and enhanced cardiac morbidity. Definition of unique efficacy and dosing parameters for GH replacement and resultant therapeutic efficacy markers in true IAGHD requires prospective study.

Incidence of second neoplasm in childhood cancer survivors treated with GH: an analysis of GeNeSIS and HypoCCS

OBJECTIVE

Childhood cancer survivors are commonly treated with GH for GH deficiency that develops either as a result of primary malignancy or its treatment. One study--the Childhood Cancer Survivor Study (CCSS)--demonstrated increased risk of second neoplasm (SN) in GH-treated childhood cancer survivors compared with non-GH treated, after adjusting for key risk factors. We assessed the incidence of SN in GH-treated childhood cancer survivors in outpatient observational studies of GH replacement.

DESIGN

Retrospective analysis of two prospective cohort studies that collected data on safety of GH replacement as prescribed in clinical practice.

METHODS

Childhood cancer survivors enrolled in Eli Lilly and Company's pediatric (Genetics and Neuroendocrinology of Short Stature International Study (GeNeSIS)) and adult (Hypopituitary Control and Complications Study (HypoCCS)) observational studies of GH treatment were assessed for incidence of SN.

RESULTS

The percentage of childhood cancer survivors treated with GH who developed a SN was 3.8% in pediatric GeNeSIS participants and 6.0% in adult HypoCCS participants. The estimated cumulative incidence of SN at 5 years of follow-up in these studies was 6.2 and 4.8% respectively.

CONCLUSIONS

The incidence of SN in GeNeSIS and HypoCCS GH-treated participants is similar to the published literature and is thus consistent with increased risk of SN in childhood cancer survivors treated with GH. As follow-up times were relatively short (<3 years), longer observation is recommended. Nevertheless, clinicians should be alerted to the possibility of increased risk of SN in childhood cancer survivors treated with GH and continue chronic surveillance.

Prospective safety surveillance of GH-deficient adults: comparison of GH-treated vs untreated patients

CONTEXT

In clinical practice, the safety profile of GH replacement therapy for GH-deficient adults compared with no replacement therapy is unknown.

OBJECTIVE

The objective of this study was to compare adverse events (AEs) in GH-deficient adults who were GH-treated with those in GH-deficient adults who did not receive GH replacement.

DESIGN AND SETTING

This was a prospective observational study in the setting of US clinical practices.

PATIENTS AND OUTCOME MEASURES

AEs were compared between GH-treated (n = 1988) and untreated (n = 442) GH-deficient adults after adjusting for baseline group differences and controlling the false discovery rate. The standardized mortality ratio was calculated using US mortality rates.

RESULTS

After a mean follow-up of 2.3 years, there was no significant difference in rates of death, cancer, intracranial tumor growth or recurrence, diabetes, or cardiovascular events in GH-treated compared with untreated patients. The standardized mortality ratio was not increased in either group. Unexpected AEs (GH-treated vs untreated, P ≤ .05) included insomnia (6.4% vs 2.7%), dyspnea (4.2% vs 2.0%), anxiety (3.4% vs 0.9%), sleep apnea (3.3% vs 0.9%), and decreased libido (2.1% vs 0.2%). Some of these AEs were related to baseline risk factors (including obesity and cardiopulmonary disease), higher GH dose, or concomitant GH side effects.

CONCLUSIONS

In GH-deficient adults, there was no evidence for a GH treatment effect on death, cancer, intracranial tumor recurrence, diabetes, or cardiovascular events, although the follow-up period was of insufficient duration to be conclusive for these long-term events. The identification of unexpected GH-related AEs reinforces the fact that patient selection and GH dose titration are important to ensure safety of adult GH replacement.

Efficacy and safety of growth hormone replacement therapy in Japanese adults with growth hormone deficiency: a post-marketing observational study

This large-scale observational study examined the long-term effectiveness and safety of growth hormone (GH) replacement therapy for adult GH deficiency (GHD) in Japanese clinical practice using the Hypopituitary Control and Complications Study database. The study included 402 GHD patients for safety analyses and a subset of 209 patients (149 adult-onset and 60 childhood-onset GHD patients) who had not previously received GH replacement therapy for the efficacy analyses. Data on clinical, metabolic, quality of life (QoL) characteristics, and all adverse events (AEs) were collected at baseline (start of GH treatment), 6 months, 1 year and 2 years. Over the observation period, there were improvements from baseline in insulin-like growth factor-I standard deviation scores (P<0.001), although the changes in metabolic parameters were minimal. QoL (Short Form-36) Z-scores significantly increased from baseline in both onset-type groups for several subscale domains (P<0.05). A total of 145 (36.1%) patients experienced ≥1 AE. Common AEs were hyperlipidaemia (2.7%) and hyperinsulinaemia (2.2%). Some patients experienced recurrent hypothalamic/pituitary tumour (events per 1000 patient-years: 2.78), new benign (0.93), malignant tumour (10.28) or other new tumour (0.93), new diabetes mellitus (7.45), and new stroke (3.71). Seven patients died during the observation period. Our safety findings are inconclusive about the associations between GH replacement and AEs, although the incidence of diabetes mellitus and cardiovascular events are similar to those reported in the Japanese general population. In conclusion, the key beneficial effects of GH replacement therapy for GHD are observed in routine clinical practice in Japan.

Variation of the baseline characteristics and treatment parameters over time: an analysis of 15 years of growth hormone replacement in adults in the German KIMS database

The purpose of this study is to examine potential implications of changes in the approach to adult growth hormone (GH) replacement (GHR) over the last 15 years. Therefore, we analysed the German KIMS database as one of the largest single country pharmacoepidemiological databases on adult GH deficiency (GHD). Based on the date of their first GH application patients were assigned to three intervals (1995-1999, 2000-2004, 2005-2009). A multivariate analysis of variance with interval and sex as independent variables was conducted. Differences were analysed with respect to IGF-I standard deviation score (SDS), quality of life, latency between GHD diagnosis and first GH dose, body mass index, waist-hip ratio, lipid profile, and GH dose. All analyses were conducted at baseline, 1 year, and 3 years of GHR. We detected significant associations between time interval and patient characteristics at baseline and with treatment effects. Recently, patients with less severe GHD (mean IGF-I SDS: -2.1, -1.6, -1.0 in the 1st, 2nd and 3rd interval; p = 0.000) are treated with lower GH starting doses (mean 0.30, 0.19, 0.21 mg/day in the 1st, 2nd and 3rd interval; p = 0.000). In the first time interval, IGF-I SDS was not normalized in females after 3 years of GHR. The results of our analysis demonstrate prominent changes in patient characteristics and handling of GHR. They highlight that approach to therapy and patient inclusion criteria change over time and may represent an important confounder for any analysis in epidemiological surveillance surveys.

Testing for growth hormone deficiency in adults: doing without growth hormone-releasing hormone

PURPOSE OF REVIEW

This article summarizes recent advances in testing for growth hormone deficiency (GHD) in adults, focusing on critical appraisal of existing growth hormone (GH) provocative tests as well as newer tests in development.

RECENT FINDINGS

The diagnosis of GHD can be challenging and often requires the use of GH provocative testing. The most widely validated of these is insulin-induced hypoglycemia (ITT), which requires close supervision and has significant contraindications and side-effects. The arginine-growth hormone-releasing hormone (GHRH) test had become widely used as a safe and accurate alternative to the ITT, but GHRH is currently unavailable for clinical use in the USA. On the basis of review of recent literature we recommend that in the absence of GHRH, glucagon stimulation testing should be the preferred alternative to ITT. Several synthetic GH secretagogues that mimic the gastric peptide ghrelin are currently in development and may become available for use in the diagnosis of GHD in the near future. Other GH provocative tests suitable for use in children lack adequate specificity for the diagnosis of GHD in adults.

SUMMARY

Due to the current unavailability of the arginine-GHRH test in the USA, when ITT is contraindicated or impractical we recommend the glucagon stimulation testing as the GH provocative test of choice. There remains a need for a simple, safe and accurate test for the diagnosis of GHD.

Diagnosing growth hormone deficiency in adults

Adult growth hormone (GH) deficiency is a recognised syndrome associated with adverse phenotypic, metabolic, and quality-of-life features which improve in many patients when GH is substituted. The appropriate selection of patients at risk of growth hormone deficiency (GHD) is the crucial first step in arriving at a correct diagnosis. Although multiple diagnostic modalities are available including a 24-hour serum GH profile, stimulated GH levels, and insulin-like growth factor-1 (IGF-1) levels, the use of dynamic tests for GH reserves is required in most cases. This paper discusses the utility and drawbacks of the various testing modalities with reference to international guidelines. Regardless of the test chosen, clinical pitfalls including age and obesity must be taken into account. In addition, there is considerable analytical variation in the biochemical measurements of GH and IGF-1 which must be considered before making a diagnosis of GHD in adulthood.

Does growth hormone replacement therapy reduce mortality in adults with growth hormone deficiency? Data from the Dutch National Registry of Growth Hormone Treatment in adults

CONTEXT

Adults with GH deficiency (GHD) have a decreased life expectancy. The effect of GH treatment on mortality remains to be established.

OBJECTIVE

This nationwide cohort study investigates the effect of GH treatment on all-cause and cause-specific mortality and analyzes patient characteristics influencing mortality in GHD adults.

DESIGN, SETTING, AND PATIENTS

Patients in the Dutch National Registry of Growth Hormone Treatment in Adults were retrospectively monitored (1985-2009) and subdivided into treatment (n = 2229), primary (untreated, n = 109), and secondary control (partly treated, n = 356) groups.

MAIN OUTCOME MEASURES

Standardized mortality ratios (SMR) were calculated for all-cause, malignancy, and cardiovascular disease (CVD) mortality. Expected mortality was obtained from cause, sex, calendar year, and age-specific death rates from national death and population counts.

RESULTS

In the treatment group, 95 patients died compared to 74.6 expected [SMR 1.27 (95% confidence interval, 1.04-1.56)]. Mortality was higher in women than in men. After exclusion of high-risk patients, the SMR for CVD mortality remained increased in women. Mortality due to malignancies was not elevated. In the control groups mortality was not different from the background population. Univariate analyses demonstrated sex, GHD onset, age, and underlying diagnosis as influencing factors.

CONCLUSIONS

GHD men receiving GH treatment have a mortality rate not different from the background population. In women, after exclusion of high-risk patients, mortality was not different from the background population except for CVD. Mortality due to malignancies was not elevated in adults receiving GH treatment. Next to gender, the heterogeneous etiology is of influence on mortality in GHD adults with GH treatment.

Adult growth hormone deficiency

Adult growth hormone deficiency (AGHD) is being recognized increasingly and has been thought to be associated with premature mortality. Pituitary tumors are the commonest cause for AGHD. Growth hormone deficiency (GHD) has been associated with neuropsychiatric-cognitive, cardiovascular, neuromuscular, metabolic, and skeletal abnormalities. Most of these can be reversed with growth hormone therapy. The insulin tolerance test still remains the gold standard dynamic test to diagnose AGHD. Growth hormone is administered subcutaneously once a day, titrated to clinical symptoms, signs and IGF-1 (insulin like growth factor-1). It is generally well tolerated at the low-doses used in adults. Pegylated human growth hormone therapy is on the horizon, with a convenient once a week dosing.

Assessment of primary cancers in GH-treated adult hypopituitary patients: an analysis from the Hypopituitary Control and Complications Study

OBJECTIVE

GH and IGFs have mitogenic properties, causing speculation that GH treatment could increase risk of malignancy. While studies in GH-treated childhood cancer survivors have suggested a slight increase in second neoplasms, studies in GH-treated adults have been equivocal. Design Incidence of de novo and second cancers was evaluated in 6840 GH-treated and 940 non GH-treated adult patients in the Hypopituitary Control and Complications Study pharmacoepidemiological database.

METHODS

Evident cancer cases were evaluated in the main analysis, with sensitivity analyses including probable and possible cancers. Standardized incidence ratios (SIRs) for cancers were calculated using Surveillance, Epidemiology and End Results for the USA and GLOBOCAN for all other countries.

RESULTS

During the mean follow-up of 3.7 years/GH-treated patient, 142 evident cancer cases were identified, giving an overall SIR of 0.88 (95% confidence interval (CI) 0.74-1.04); 95% CIs included the value of 1.0 for each country examined. The SIR for GH-treated patients from the USA (71 cases) was 0.94 (95% CI 0.73-1.18), and for non GH-treated patients from the USA (27 cases) was 1.16 (95% CI 0.76-1.69). For GH-treated patients from the USA aged <35 years, the SIR (six cases) was 3.79 (1.39-8.26), with SIR not elevated for all other age categories; SIR for patients from the USA with childhood onset (CO) GH deficiency (GHD) was 2.74 (95% CI 1.18-5.41). The SIR for colorectal cancer in GH-treated patients (11 cases) was 0.60 (95% CI 0.30-1.08).

CONCLUSIONS

With relatively short follow-up, the overall primary cancer risk in 6840 patients receiving GH as adults was not increased. Elevated SIRs were found for subgroups in the USA cohort defined by age <35 years or CO GHD.

Clinical characteristics of Japanese adults with growth hormone deficiency: a HypoCCS database study

The clinical characteristics of Caucasian adults with growth hormone (GH) deficiency (GHD) have been well defined. However, no large-scale clinical practice study has examined the clinical characteristics of Japanese adults with GHD. The aim of our study was to describe the clinical characteristics of Japanese adults with GHD by reviewing the records of participants who were GH-naive at the time of enrollment in the Hypopituitary Control and Complications Study (N = 349). The majority of participants (280 of 349; 80.2%) had adult-onset rather than childhood-onset GHD. Hypothalamo-pituitary tumors were the most common cause of GHD in Japanese adults (247 of 349; 70.8%); these tumors were primarily pituitary adenomas in participants with adult-onset GHD (156 of 243; 64.2%), and germ cell tumors (19 of 40; 47.5%) and craniopharyngiomas (18 of 40; 45.0%) in participants with childhood-onset GHD. Most participants (310 of 349; 88.8%) had multiple pituitary hormone deficiencies. Dyslipidemia (195 of 349; 55.9%), visual field loss (67 of 349; 19.2%), hypertension (59 of 349; 16.9%), and liver disease (54 of 349; 15.5%) were the most common pre-existing conditions in Japanese adults with GHD. Quality of life was decreased in seven of the eight short form-36 domains in participants with GHD compared with age- and sex-matched healthy Japanese individuals. Our findings confirm that the clinical characteristics of Japanese adults with GHD are similar to those of Caucasian adults with GHD. Confirmation of these clinical characteristics will enhance the ability of clinicians to identify and treat Japanese adults with GHD.

The diagnosis and treatment of growth hormone deficiency in adults

PURPOSE OF REVIEW

This review summarizes the recent published information regarding efficacy and complications of growth hormone replacement therapy. Several recent reports have monitored patients for periods of up to 10 years. Additionally, a consensus conference has been held regarding needed improvements in diagnostic testing and the recommendations of consensus panels regarding diagnostic criteria and laboratory test utilization are summarized.

RECENT FINDINGS

Long-term studies show growth hormone can be administered safely and that muscle strength and function as well as lipoprotein abnormalities and low-bone mineral density show sustained improvement over extended periods of time. The complications that occur are generally dose-dependent and once attenuated do not tend to recur. Long-term safety studies regarding improvement in cardiovascular mortality and/or worsening prognosis for patients who develop malignancies are available only in the form of observational studies and randomized controlled long-term trial information is not yet available. The studies reported provide a means for clinicians to ascertain the patients who are likely to derive the greatest benefit from growth hormone when the appropriate diagnostic testing and treatment paradigms are utilized.

SUMMARY

The studies that are summarized provide useful information for assessing the response to treatment, selecting patients who are candidates for long-term replacement therapy and for selecting those in whom the need for therapy may need to be reassessed.

Metabolic, cardiovascular, and cerebrovascular outcomes in growth hormone-deficient subjects with previous cushing's disease or non-functioning pituitary adenoma

CONTEXT

Previous exposure to hypercortisolism due to Cushing's disease (CD) may adversely affect long-term metabolic and cardiovascular outcomes. In particular, metabolic and cardiovascular outcomes of patients with previous CD who require GH replacement have not been fully established.

OBJECTIVE

The aim of the study was to compare the prevalence and incidence of metabolic syndrome (Adult Treatment Panel III criteria), diabetes mellitus, cardiovascular disease, and cerebrovascular disease in GH-treated subjects with previous CD with GH-treated subjects with previous nonfunctioning pituitary adenoma (NFPA).

DESIGN

We conducted post hoc analysis of the observational Hypopituitary Control and Complications Study conducted at 362 international centers (1995-2006).

SUBJECTS

We studied adult-onset GH-deficient subjects with previous CD (n = 160) or NFPA (n = 879). All subjects received GH replacement therapy and were GH naive at enrollment. Multiple pituitary deficits were prevalent in both groups.

MAIN OUTCOME MEASURES

We measured the prevalence and incidence of metabolic syndrome, diabetes mellitus, cardiovascular disease, and cerebrovascular disease at baseline and at 3 yr, standardized for age and sex differences between groups.

RESULTS

Compared with subjects with previous NFPA, subjects with previous CD had a significantly greater 3-yr incidence of metabolic syndrome (CD, 23.4%; NFPA, 9.2%; P = 0.01), baseline (CD, 6.3%; NFPA, 2.2%; P < 0.01) and 3-yr (CD, 7.6%; NFPA, 3.9%; P = 0.04) prevalence of cardiovascular disease, and baseline (CD, 6.4%; NFPA, 1.8%; P = 0.03) and 3-yr (CD, 10.2%; NFPA, 2.9%; P = 0.01) prevalence of cerebrovascular disease.

CONCLUSIONS

Previous hypercortisolism may predispose GH-treated, GH-deficient subjects with prior CD to an increased risk of metabolic syndrome, cardiovascular disease, and cerebrovascular disease.

Etiology, baseline characteristics, and biochemical diagnosis of GH deficiency in the adult: are there regional variations?

Previous work has examined potential links between the etiology of GH deficiency (GHD) and the baseline characteristics of the patients including biochemical and psychometric parameters. Using an update of the KIMS pharmaco-epidemiological database (Pfizer International Metabolic Database), we addressed the question how well such results can be generalized and whether regional differences may play a role. From 30 different countries, 13 167 GH-deficient patients were included in KIMS at the data close in December 2008. In order to explore country-specific differences of baseline characteristics documented in KIMS, separate analyses of baseline characteristics of adult-onset GHD patients (n=7708) were performed for the six largest contributing European countries and the United States. This analysis revealed striking regional variations in the pathogenesis of the disease, clinical characteristics such as body mass index, and in the classical features of the metabolic syndrome such as blood pressure or lipid status between countries. Moreover, the approach to endocrine function testing was widely different between countries, as well as the distribution of etiologies of GHD. These data suggest that a complex relation between biochemical and clinical signs of GHD exists, and that the spectrum of adult GHD syndrome is influenced by regional diagnostic and clinical particularities.

Adult GH deficiency throughout lifetime

It is now accepted that adults with severe GH deficiency (GHD) demonstrate impaired physical and psychological well-being and may benefit from replacement with recombinant human GH. Post-marketing surveillance surveys, such as the Pfizer International Metabolic Database (KIMS), were initially set-up to provide safety data on long-term treatment but have the added benefit of providing ongoing observational data on the effect of GH replacement on body composition, lipid and glucose status, hypertension, bone density and quality of life. These data demonstrate that although GHD has clinical impact at all ages, the individual consequences of this condition may take on greater significance at different stages in life. At all ages, accurate, safe diagnosis and appropriate GH dosing are necessary to provide the individual with the best possible outcome.

Clinical review: Is lack of recombinant growth hormone (GH)-releasing hormone in the United States a setback or time to consider glucagon testing for adult GH deficiency?

CONTEXT

The use of the combined GHRH and arginine (GHRH-ARG) test has gained increasing acceptance in the United States as a reliable alternative test to the insulin tolerance test (ITT) for diagnosing adult GH deficiency (GHD). In July 2008, the only manufacturer of recombinant GHRH in the United States, EMD Serono, Inc., announced the discontinuation of Geref, thus raising the question of which reliable alternative GH stimulation test should practicing endocrinologists be considering in place of the GHRH-ARG test. In this article, we review the existing published data and consensus guidelines and provide recommendations for alternative stimulation tests to the GHRH-ARG test.

EVIDENCE ACQUISITION

The major source of data acquisition included PubMed search strategies and personal experience of the authors from clinical experience.

EVIDENCE SYNTHESIS

Previous consensus guidelines and previous data assessing the reliability and discriminatory value of the GHRH-ARG, glucagon, ARG, and GH secretagogues on assessing GH reserve are discussed. Our recommendations for performing the glucagon stimulation test, potential drawbacks in conducting this test, and caveats in interpreting this test are also discussed.

CONCLUSIONS

The ITT should remain the test of choice in diagnosing adult GHD. However, when the ITT is not desirable and recombinant GHRH remains unavailable in the United States, we recommend the alternative to the GHRH-ARG test to be the glucagon stimulation test, based on its reliability and availability. Nevertheless, further studies into alternative GH stimulation tests that are available in the United States, comparable, and simpler to perform than the ITT in diagnosing adult GHD are still needed.