How many tests are required to diagnose growth hormone (GH) deficiency in adults?

Isolated anterior pituitary dysfunction in adulthood

Hypopituitarism is defined as a complete or partial deficiency in one or more pituitary hormones. Anterior hypopituitarism includes secondary adrenal insufficiency, central hypothyroidism, hypogonadotropic hypogonadism, growth hormone deficiency and prolactin deficiency. Patients with hypopituitarism suffer from an increased disability and sick days, resulting in lower health status, higher cost of care and an increased mortality. In particular during adulthood, isolated pituitary deficits are not an uncommon finding; their clinical picture is represented by vague symptoms and unclear signs, which can be difficult to properly diagnose. This often becomes a challenge for the physician. Aim of this narrative review is to analyse, for each anterior pituitary deficit, the main related etiologies, the characteristic signs and symptoms, how to properly diagnose them (suggesting an easy and reproducible step-based approach), and eventually the treatment. In adulthood, the vast majority of isolated pituitary deficits are due to pituitary tumours, head trauma, pituitary surgery and brain radiotherapy. Immune-related dysfunctions represent a growing cause of isolated pituitary deficiencies, above all secondary to use of oncological drugs such as immune checkpoint inhibitors. The diagnosis of isolated pituitary deficiencies should be based on baseline hormonal assessments and/or dynamic tests. Establishing a proper diagnosis can be quite challenging: in fact, even if the diagnostic methods are becoming increasingly refined, a considerable proportion of isolated pituitary deficits still remains without a certain cause. While isolated ACTH and TSH deficiencies always require a prompt replacement treatment, gonadal replacement therapy requires a benefit-risk evaluation based on the presence of comorbidities, age and gender of the patient; finally, the need of growth hormone replacement therapies is still a matter of debate. On the other side, prolactin replacement therapy is still not available. In conclusion, our purpose is to offer a broad evaluation from causes to therapies of isolated anterior pituitary deficits in adulthood. This review will also include the evaluation of uncommon symptoms and main etiologies, the elements of suspicion of a genetic cause and protocols for diagnosis, follow-up and treatment.

Macimorelin as a Diagnostic Test for Adult GH Deficiency

PURPOSE

The diagnosis of adult GH deficiency (AGHD) is challenging and often requires confirmation with a GH stimulation test (GHST). The insulin tolerance test (ITT) is considered the reference standard GHST but is labor intensive, can cause severe hypoglycemia, and is contraindicated for certain patients. Macimorelin, an orally active GH secretagogue, could be used to diagnose AGHD by measuring stimulated GH levels after an oral dose.

MATERIALS AND METHODS

The present multicenter, open-label, randomized, two-way crossover trial was designed to validate the efficacy and safety of single-dose oral macimorelin for AGHD diagnosis compared with the ITT. Subjects with high (n = 38), intermediate (n = 37), and low (n = 39) likelihood for AGHD and healthy, matched controls (n = 25) were included in the efficacy analysis.

RESULTS

After the first test, 99% of macimorelin tests and 82% of ITTs were evaluable. Using GH cutoff levels of 2.8 ng/mL for macimorelin and 5.1 ng/mL for ITTs, the negative agreement was 95.38% (95% CI, 87% to 99%), the positive agreement was 74.32% (95% CI, 63% to 84%), sensitivity was 87%, and specificity was 96%. On retesting, the reproducibility was 97% for macimorelin (n = 33). In post hoc analyses, a GH cutoff of 5.1 ng/mL for both tests resulted in 94% (95% CI, 85% to 98%) negative agreement, 82% (95% CI, 72% to 90%) positive agreement, 92% sensitivity, and 96% specificity. No serious adverse events were reported for macimorelin.

CONCLUSIONS

Oral macimorelin is a simple, well-tolerated, reproducible, and safe diagnostic test for AGHD with accuracy comparable to that of the ITT. A GH cutoff of 5.1 ng/mL for the macimorelin test provides an excellent balance between sensitivity and specificity.

The prevalence of growth hormone deficiency in survivors of subarachnoid haemorrhage: results from a large single centre study

OBJECTIVE

The variation in reported prevalence of growth hormone deficiency (GHD) post subarachnoid haemorrhage (SAH) is mainly due to methodological heterogeneity. We report on the prevalence of GHD in a large cohort of patients following SAH, when dynamic and confirmatory pituitary hormone testing methods are systematically employed.

DESIGN

In this cross-sectional study, pituitary function was assessed in 100 patients following SAH. Baseline pituitary hormonal profile measurement and glucagon stimulation testing (GST) was carried out in all patients. Isolated GHD was confirmed with an Arginine stimulation test and ACTH deficiency was confirmed with a short synacthen test.

RESULTS

The prevalence of hypopituitarism in our cohort was 19% and the prevalence of GHD was 14%. There was no association between GHD and the clinical or radiological severity of SAH at presentation, treatment modality, age, or occurrence of vasospasm. There were statistically significant differences in terms of Glasgow Outcome Scale (GOS; p = 0.03) between patients diagnosed with GHD and those without. Significant inverse correlations between GH peak on GST with body mass index (BMI) and waist hip ratio (WHR) was also noted (p < 0.0001 and p < 0.0001 respectively).

CONCLUSION

Using the current testing protocol, the prevalence of GHD detected in our cohort was 14%. It is unclear if the BMI and WHR difference observed is truly due to GHD or confounded by the endocrine tests used in this protocol. There is possibly an association between the development of GHD and worse GOS score. Routine endocrine screening of all SAH survivors with dynamic tests is time consuming and may subject many patients to unnecessary side-effects. Furthermore the degree of clinical benefit derived from growth hormone replacement in this patient group, remains unclear. Increased understanding of the most appropriate testing methodology in this patient group and more importantly which SAH survivors would derive most benefit from GHD screening is required.

Patient reported outcome in posttraumatic pituitary deficiency: results from The Danish National Study on posttraumatic hypopituitarism

OBJECTIVE

Posttraumatic pituitary hormone deficiency is often suggested. The impact of these predominantly mild and often irreproducible deficiencies on outcome is less clear. The aim of the present study was to describe patient reported outcome in a national a priori unselected cohort of patients with traumatic brain injury (TBI) in relation to deficiencies identified upon pituitary assessment.

DESIGN AND METHODS

We conducted a nationwide population-based cohort study. Participants were Danish patients with a head trauma diagnosis recorded in the Danish Board of Health diagnostic code registry; 439 patients (and 124 healthy controls) underwent assessment of anterior pituitary function 2.5 years (median) after TBI. Questionnaires on health-related quality of life (QoL) (SF36, EuroQoL-5D, QoL assessment of GH deficiency in adults) and fatigue (MFI-20) were completed in parallel to pituitary assessment.

RESULTS

Patients with TBI had significant detriments in QoL. Impairment (mainly physical scales) related to pituitary deficiency, although only partially confirmed after adjustment for demographic differences. Hypogonadotropic hypogonadism related to several QoL scores. Increasing impairments were observed with declining total testosterone concentrations (men), but not free testosterone concentrations or any other hormone concentrations. Total testosterone was not independently related to impaired QoL and fatigue, after adjustment for demographics, and treatment with antidiabetics, opioids, antidepressants, and anticonvulsants.

CONCLUSIONS

Only a very limited relationship between pituitary hormone deficiencies and QoL/fatigue was demonstrated. Due to the dominating influence of concurrent comorbidities, pituitary deficiencies were not independently related to QoL/fatigue. Causality is still to be shown, and whether substitution therapy could be of additional relevance in selected patients needs to be proven.

Low prevalence of hypopituitarism after subarachnoid haemorrhage using confirmatory testing and with BMI-specific GH cut-off levels

OBJECTIVE

Hypopituitarism following subarachnoid haemorrhage (SAH) has been reported to be a frequent occurrence. However, there is considerable heterogeneity between studies with differing patient populations and treatment modalities and most importantly employing differing endocrine protocols and (normal) reference ranges of GH. We aimed to examine prospectively a cohort of SAH survivors for development of hypopituitarism post-SAH using rigorous endocrine testing and compare GH response to glucagon stimulation with a cohort of healthy controls of a similar BMI.

DESIGN AND METHODS

Sixty-four patients were investigated for evidence of hypopituitarism 3 months post-SAH with 50 patients tested again at 12 months. Glucagon stimulation testing (GST), with confirmation of deficiencies by GHRH/arginine testing for GH deficiency (GHD) and short synacthen testing for ACTH deficiency, was used. Basal testing of other hormonal axes was undertaken.

RESULTS

Mean age of patients was 53±11.7 years and mean BMI was 27.5±5.7 kg/m(2). After confirmatory testing, the prevalence of hypopituitarism was 12% (GHD 10%, asymptomatic hypocortisolaemia 2%). There was no association between hypopituitarism and post-SAH vasospasm, presence of cerebral infarction, Fisher grade, or clinical grading at presentation. There was a significant correlation between BMI and peak GH to glucagon stimulation in both patients and controls.

CONCLUSIONS

Identification of 'true' GHD after SAH requires confirmatory testing with an alternative stimulation test and application of BMI-specific cut-offs. Using such stringent criteria, we found a prevalence of hypopituitarism of 12% in our population.

The accuracy of diagnostic tests for GH deficiency in adults: a systematic review and meta-analysis

CONTEXT

The diagnostic accuracy of tests used to diagnose GH deficiency (GHD) in adults is unclear.

OBJECTIVE

We conducted a systematic review and meta-analysis of studies that provided data on the available diagnostic tests.

DATA SOURCES

We searched electronic databases (MEDLINE, EMBASE, Cochrane CENTRAL, Web of Sciences, and Scopus) through April 2011.

STUDY SELECTION

Review of reference lists and contact with experts identified additional candidate studies. Reviewers, working independently and in duplicate, determined study eligibility.

DATA EXTRACTION

reviewers, working independently and in duplicate, determined the methodological quality of studies and collected descriptive, quality, and outcome data.

DATA SYNTHESIS

Twenty-three studies provided diagnostic accuracy data; none provided patient outcome data. Studies had fair methodological quality, used several reference standards, and included over 1100 patients. Several tests based on direct or indirect stimulation of GH release were associated with good diagnostic accuracy, although most were assessed in one or two studies decreasing the strength of inference due to small sample size. Serum levels of GH or IGF1 had low diagnostic accuracy. Pooled sensitivity and specificity of the two most commonly used stimulation tests were found to be 95 and 89% for the insulin tolerance test and 73 and 81% for the GHRH+arginine test respectively. Meta-analytic estimates for accuracy were associated with substantial heterogeneity.

CONCLUSION

Several tests with reasonable diagnostic accuracy are available for the diagnosis of GHD in adults. The supporting evidence, however, is at high risk of bias (due to heterogeneity, methodological limitations, and imprecision).

Subnormal serum insulin-like growth factor-I levels in young adults with childhood-onset nonacquired growth hormone (GH) deficiency who recover normal gh secretion may indicate less severe but persistent pituitary failure

CONTEXT

The unexpected observation of a normal GH peak in 22% of young adults with childhood-onset GH deficiency (GHD) and ectopic neurohypophysis has raised questions about the criteria defining GHD in young adults and whether patients with subsequent increases in GH secretion nonetheless have a subtle form of GHD.

OBJECTIVE

Our objective was to determine the characteristics of patients with childhood-onset nonacquired GHD who recover normal peak GH secretion when adult height has been achieved.

DESIGN AND SETTING

We conducted a university hospital-based observational follow-up study.

PARTICIPANTS

Sixty-two patients with ectopic neurohypophysis (n = 24), isolated hypoplastic anterior pituitary (n = 14), or normal hypothalamic pituitary area (n = 24) on magnetic resonance imaging (MRI) at the time of GHD diagnosis underwent reevaluation of the GH-IGF-I axis at a mean age of 16.8 +/- 1.6 yr.

MAIN OUTCOME MEASURES

Outcome measures included clinical and MRI findings and serum IGF-I and peak GH levels.

RESULTS

On retesting, peak GH exceeded 10 microg/liter in 31 patients (50%): six (20%) patients with ectopic neurohypophysis, 10 (32%) patients with initially isolated hypoplastic anterior pituitary, and 15 (48%) patients with normal MRI findings. Among these patients, serum IGF-I levels were significantly lower in patients with ectopic neurohypophysis than in those without structural abnormalities of the hypothalamic pituitary axis (n = 25), but patients without structural abnormalities also had significantly lower serum IGF-I levels than control subjects, after controlling for age, sex, and body mass index (mean serum IGF-I levels of 374 +/- 83 vs. 446 +/- 108 microg/liter; beta-coefficient = -72; P = 0.003).

CONCLUSIONS

The severity of the disease seems to have decreased over time in these patients, who may nonetheless present persistent pituitary failure. The natural history and clinical implications of these findings remain to be clarified. The possibility of a deterioration in the secretion of GH and other pituitary hormones later in life in a subset of these patients warrants the careful long-term follow-up of this population.

Defining Growth Hormone Status in Adults with Hypopituitarism

The identification of adults with severe growth hormone (GH) deficiency (GHD) is not straightforward. The insulin tolerance test remains the gold standard diagnostic test, although other stimuli such as GH-releasing hormone-arginine are gaining acceptance. Insulin-like growth factor-I has a poor diagnostic sensitivity in adult-onset GHD, but is more useful in the subgroup of adults with childhood-onset GHD. Therapeutic developments include increasing recognition of the need to continue GH therapy beyond final height in young adults with severe GHD on retesting. Consensus guidelines have provided a useful algorithm to identify individuals requiring retesting and the number of tests needed. The concept of partial GHD, recognized by paediatric endocrinologists for many years, is being examined in adults with hypothalamic-pituitary disease. Preliminary evidence suggests that this entity is associated with metabolic and anthropometric abnormalities intermediate between those in severe GHD and in healthy controls. It remains to be seen whether this subgroup will derive benefit from GH therapy. To date, therapeutic benefits of GH have been demonstrated only in adults with severe GHD. It is, therefore, imperative that these individuals are unequivocally identified; the diagnosis becomes more uncertain in the presence of obesity, increasing age, and in the absence of additional pituitary hormone deficits.

The Phenotype of Adults with Partial Growth Hormone Deficiency

The concept of partial growth hormone (GH) deficiency (GHD) is well established within the paediatric setting having been validated against height velocity. In hypopituitary adults, GHD is defined by a peak GH response <3 microg/l to stimulation. This cut-off is arbitrary due to the lack of a biological marker equivalent of height velocity. The majority of normal adults achieve peak GH levels several fold higher than this cut off during stimulation. It can be argued, therefore, that there is a cohort of hypopituitary adults with intermediate peak GH values (3-7 microg/l), who have relatively impaired GH secretion, and for whom the impact of this partial GHD (GH insufficiency, GHI) on biological endpoints is not known. Studies of GHI adults have demonstrated an abnormal body composition, adverse lipid profile, impaired cardiac performance, reduced exercise tolerance and insulin resistance. The severity of these abnormalities lies between GHD adults and normal subjects. Whether these anomalies translate into increased mortality, as observed in GHD hypopituitary adults, is not yet known. Given the presence of similar sequelae in GHI and GHD adults, and the improvements during GH replacement in GHD adults, a randomized placebo-controlled study of GH replacement in GHI patients is warranted.

Problematic determination of serum growth hormone: experience from external quality assurance surveys 1998-2003

The objective of the present study was to start a new external quality assurance survey (EQAS) for the determination of serum growth hormone (GH) using pooled serum specimens as quality-assurance samples. To give good coverage of multiple forms of GH, the specimens included sera from GH-deficient and acromegalic patients as well as from persons showing a normal response in GH provocation tests. In one survey the quality-control specimens were spiked with exogenous 22-kD GH to obtain some idea of the specificity and GH recovery of the assays. The EQA surveys of 1998-2003 were organized by Labquality of Helsinki in cooperation with three university hospital laboratories in Finland. The number of participating laboratories ranged from 8 to 14. During 1998-2003, gratifying methodological harmonization occurred in the participating group, as the participants switched to the immunometric detection principle, the number of method applications decreasing from 7 to 3. In 1998 the 14 participating laboratories reported five different conversion factors (from microg/l to mU/l), whereas in 2003 7 of the 8 participants reported the same factor. Despite the harmonization trend among participating laboratories, further efforts are needed, because marked method-based differences still exist. This dialogue should include kit manufacturers, laboratory experts, EQA organizations and clinicians using the test results.

Isolated growth hormone (GH) deficiency in adult patients: baseline clinical characteristics and responses to GH replacement in comparison with hypopituitary patients. A sub-analysis of the KIMS database

BACKGROUND

Isolated growth hormone deficiency (IGHD) provides the ideal model to characterize GHD without interference from other pituitary deficiencies or their treatment. No study has addressed the question whether adult patients with IGHD differ in clinical presentation or in responsiveness to GH replacement from adult patients with multiple pituitary hormone deficiencies (MPHD) receiving conventional replacement therapy.

PATIENTS AND METHODS

Data were retrieved from the outcomes research database KIMS (Pfizer international metabolic database). Patients with IGHD accounted for 9.6% (274/2868) of all GHD patients. Patients were separated according to the timing of onset. In the adult-onset (AO) group, 167 patients with IGHD were compared to 1992 patients with MPHD. In the childhood-onset (CO) group, 107 patients with IGHD were compared to 602 patients with MPHD. To assess the effect of GH replacement after one year, a longitudinal sub-analysis in the AO group was performed comparing 89 IGHD patients to 1234 MPHD patients. The same study was done in the CO group comparing 66 IGHD patients to 386 MPHD patients. Because IGHD patients were significantly younger than MPHD patients, data analysis was also performed after adjustment for gender and age.

RESULTS

In the AO group, non-functioning and secreting pituitary adenomas were the most common primary diagnoses in both IGHD and MPHD. Medical history revealed a high prevalence of hypertension and fractures in both subgroups, but also of non-insulin dependent diabetes mellitus. The prevalence of obesity was high and the waist circumference was elevated. The lipid profile was unfavourable in both IGHD and MPHD. IGF-I concentration and SDS were comparable in both subgroup. Quality of life assessed by QoL-AGHDA was equally poor in both IGHD and MPHD. GH replacement therapy induced favourable changes without distinction. In the CO group, the most common cause in both subgroups was idiopathic. Fracture rate was similarly prevalent in both IGHD and MPHD. Obesity was prominent in both subgroups, but BMI and waist circumference were lower in IGHD. Adverse lipid changes were similarly found in both IGHD and MPHD. IGF-I concentration and SDS were significantly higher in the IGHD subgroup compared to the MPHD subgroup. The QoL-AGHDA score was equally abnormal in both IGHD and MPHD. GH replacement achieved similar significant improvement in both subgroups.

CONCLUSIONS

GHD patients with AO-IGHD and AO-MPHD present with a similar clinical expression and respond similarly to GH replacement. Patients with CO-IGHD are less severely affected by GHD than CO-MPHD patients, but, nevertheless, both groups show a comparable adverse lipid profile and poor quality of life and respond favourably to GH replacement. These findings support the concept that GH alone is responsible for most if not all metabolic aspects of hypopituitary patients receiving conventional replacement therapy, regardless of age of onset or aetiology. As a consequence, GH replacement therapy not only has potential benefit in GHD patients with additional hormonal deficits, but also the indication of treatment must be extended to patients with isolated GHD.

Do all patients with childhood-onset growth hormone deficiency (GHD) and ectopic neurohypophysis have persistent GHD in adulthood?

Cerebral magnetic resonance imaging findings are of great value for the diagnosis of nonacquired GH deficiency (GHD), and ectopic posterior pituitary hyperintense signal (EPPHS) is a sensitive and specific indicator of hypopituitarism. It has been suggested that patients with childhood-onset GHD and EPPHS do not require additional investigation of GH secretion and should not be retested when adult height is achieved. This recommendation has never been validated through a systematic study. This study aimed to characterize the anterior pituitary function status of patients with EPPHS treated for GHD during childhood after completion of GH therapy when adult height had been achieved. Patients (n = 18; 15 males and three females) with childhood-onset GHD associated with ectopic neurohypophysis were treated with hGH (0.20 +/- 0.05 mg/kg.wk) for 9.9 +/- 4.0 yr (from 6.8 +/- 4.7 to 17.7 +/- 1.3 yr of age) with a mean height gain of 2.6 +/- 1.4 sd score. GH secretion was reevaluated by arginine insulin (n = 15) or propanolol glucagon (n = 3) test after 0.5 +/- 0.6 yr of GH withdrawal. At reevaluation, peak GH was more than 10 mug/liter in four patients (22%; range, 11.7-19.5 microg/liter; group I), between 5 and 10 microg/liter in three patients (17%; range, 7.3-9 mug/liter; group II), and less than 5 microg/liter in 11 patients (61%; range, 0-4.7 microg/liter; group III). A positive correlation was found between serum IGF-I and peak GH levels after attainment of adult height (P = 0.007). Only one of the seven patients who showed increased GH secretion ability in adulthood (groups I and II) demonstrated other hormonal deficiencies (gonadotropin and adrenal insufficiencies). Among the 11 patients with persistent severe GHD (group III), 10 (91%) of the 11 subjects were shown to have multiple pituitary hormone deficits after attainment of adult height. The structure of the hypothalamo-pituitary axis differs among groups [i.e. patients who showed increased GH secretion ability in adulthood (groups I and II) vs. those who remained severely GHD (group III)]. The location of the EPPHS was significantly different among groups (P < 0.003). The EPPHS was found at the median eminence in all but one of group III patients and along the pituitary stalk (proximal stalk) in all but one of group I and II patients. The pituitary stalk was visible and described as normal (n = 1) or thin (n = 6) in all group I and II patients, whereas the pituitary stalk was not visible even after enhancement in seven of the 11 group III patients (P < 0.02). The prevalence of anterior pituitary hypoplasia and the mean height gain sd score were similar in each group. In conclusion, only 61% of patients with childhood-onset GHD and EPPHS remained severely GHD, and thus suitable for GH therapy, in adulthood. Although the pathogenesis of anterior pituitary dysfunction remains unclear in patients with ectopic neurohypophysis, isolated GHD, location of EPPHS along the stalk, and visibility of the pituitary stalk on magnetic resonance imaging findings clearly represent important markers to predict a less severe form of the disease.

Glucagon stimulation test for the diagnosis of GH deficiency in adults

The insulin tolerance test (ITT) is considered the test of choice for the diagnosis of GH deficiency (GHD). However, in patients with contraindications to ITT, alternative provocative tests must be used with appropriate cut-offs. The glucagon stimulation test has proved to be a safe, low-cost and effective means of stimulating GH secretion, and therefore can be considered as a suitable alternative to the ITT. We have studied the GH response to the glucagon test in 33 patients with known pituitary disease, 12 males and 21 females, aged between 21 and 60 yr (41.18 +/- 9.47 yr); 5 had isolated GHD and 28 had panhypopituitarism. We also evaluated a control group of 25 individuals, matched for age and sex (8 males and 17 females), aged between 20 and 60 yr (39.28 +/- 12.10 yr). They were selected via the ITT if their peak GH response was > 5.0 ng/ml. GH peak after glucagon was significantly lower in the group of patients compared to the control group (0.49 +/- 0.85 vs 8.69 +/- 5.85 ng/ml, p = 0.0001). Receiver-operating characteristic (ROC) plot analyses of the control and GHD group showed an area under the curve of 0.982 for GH peak response to glucagon. The response value of 3.0 ng/ml showed the best pair of sensitivity (97%)/specificity (88%), and was chosen as the cut-off defining GHD. After evaluation of positive predictive values (PPV) and negative predictive values (NPV) through simulation of different prevalences of the disease, we concluded that the cut-off point of 3.00 ng/ml maximizes both PPV and NPV (100%). In conclusion, we have shown that the glucagon stimulation test has a good performance and great diagnostic accuracy for the diagnosis of GHD.

Timing of onset of growth hormone deficiency is a major influence on insulin-like growth factor I status in adult life

OBJECTIVE

Several reports have suggested that IGF-I levels in patients with childhood-onset (CO) GH deficiency are lower than those observed in patients with adult-onset (AO) GH deficiency. However, these reports are unsatisfactory as there are several differences between the cohorts studied other than the timing of onset of GH deficiency; in particular, the patients were not matched for equal severity of GH deficiency. We have pursued this question further by examining the IGF-I standard deviation score (SDS) in patients with CO and AO GH deficiency, with equal degrees of severity of GH deficiency, as defined by the peak GH response to the insulin tolerance test (ITT).

PATIENTS AND MEASUREMENTS

IGF-I SDS were compared in 146 non acromegalic patients (69 male), aged 15.7-76.6 years (median 33.4 years), bone mass index (BMI) 27.8 +/- 5.8 kg/m2, with severe GH deficiency (peak GH response < 9 mU/l to insulin-induced hypoglycaemia). Patients were subdivided by timing of onset of GH deficiency and the peak GH response to the ITT (GH response < or = 1 mU/l, group 1; > 1-3 mU/l, group 2; > 3-6 mU/l, group 3; > 6-8.9 mU/l, group 4).

RESULTS

The IGF-I SDS (mean value +/- SD) in the CO group (n = 63) as a whole was significantly lower than that found in the AO group (n = 83) (-3.7 +/- 2.8 vs.-1.55 +/- 2.2, respectively; P < 0.0001). Despite this, there was no significant difference in the peak GH response to an ITT between the two cohorts (2.8 +/- 2.3 mU/l in the AO cohort and 2.6 +/- 2.2 mU/l in the CO cohort; P = 0.5). When the cohorts were subdivided by severity of GH deficiency, there remained a significant difference in IGF-I SDS in groups 1 (P < 0.0001), 2 (P = 0.05) and 3 (P < 0.05), but there was no significant difference between the AO and CO cohorts in group 4. The peak GH response to an ITT was similar in the AO and CO cohorts in all groups (P = 0.8, 0.8, 0.9 and 0.3 in groups 1-4, respectively). Although increasing severity of hypopituitarism was associated with a decline in IGF-I SDS in the CO cohort (P < 0.01), this was not the case in the AO cohort (P = 0.3).

CONCLUSION

These data support the hypothesis that there is an innate difference between adult patients with either CO or AO GH deficiency that cannot be explained solely by variation in the severity of GH deficiency. A possible explanation is that childhood GH deficiency programmes the subsequent relationship between GH and IGF-I in adult life or that the body composition changes, which are more severe in AO GH deficiency, influence IGF-I status.

Childhood-onset growth hormone (GH) deficiency in adult life

Over the last decade GH replacement therapy for adults has progressed in status from research study to a mainstream clinical indication. An area ripe for further research, however, is the difference between adults who developed GHD before and after completion of growth and puberty. That differences exist, not only in aetiology, but also in phenotype and response to GH therapy is clear. However, whether these differences are intrinsic to the timing of onset of GHD, or related to secondary factors including the method of assessment or dose of GH employed is uncertain. This chapter discusses the current state of knowledge in this area and poses further questions, not only for the researcher attempting to understand the mechanisms underlying these differences, but also for the physician seeking to ameliorate the impact of GHD in patients who acquired GHD in childhood.

Sensitivity and specificity of six tests for the diagnosis of adult GH deficiency

Although the use of the insulin tolerance test (ITT) for the diagnosis of adult GH deficiency is well established, diagnostic peak GH cut-points for other commonly used GH stimulation tests are less clearly established. Despite that fact, the majority of patients in the United States who are evaluated for GH deficiency do not undergo insulin tolerance testing. The aim of this study was to evaluate the relative utility of six different methods of testing for adult GH deficiency currently used in practice in the United States and to develop diagnostic cut-points for each of these tests. Thirty-nine patients (26 male, 13 female) with adult-onset hypothalamic-pituitary disease and multiple pituitary hormone deficiencies were studied in comparison with age-, sex-, estrogen status-, and body mass index-matched control subjects (n = 34; 20 male, 14 female). A third group of patients (n = 21) with adult-onset hypothalamic-pituitary disease and no more than one additional pituitary hormone deficiency was also studied. The primary end-point was peak serum GH response to five GH stimulation tests administered in random order at five separate visits: ITT, arginine (ARG), levodopa (L-DOPA), ARG plus L-DOPA, and ARG plus GHRH. Serum IGF-I concentrations were also measured on two occasions. For purposes of analysis, patients with multiple pituitary hormone deficiencies were assumed to be GH deficient. Three diagnostic cut-points were calculated for each test to provide optimal separation of multiple pituitary hormone deficient and control subjects according to three criteria: 1) to minimize misclassification of control subjects and deficient patients (balance between high sensitivity and high specificity); 2) to provide 95% sensitivity for GH deficiency; and 3) to provide 95% specificity for GH deficiency. The greatest diagnostic accuracy occurred with the ITT and the ARG plus GHRH test, although patients preferred the latter (P = 0.001). Using peak serum GH cut-points of 5.1 microg/liter for the ITT and 4.1 microg/liter for the ARG plus GHRH test, high sensitivity (96 and 95%, respectively) and specificity (92 and 91%, respectively) for GH deficiency were achieved. To obtain 95% specificity, the peak serum GH cut-points were lower at 3.3 microg/liter and 1.5 microg/liter for the ITT and ARG plus GHRH test, respectively. There was substantial overlap between patients and control subjects for the ARG plus L-DOPA, ARG, and L-DOPA tests, but test-specific cut-points could be defined for all three tests to provide 95% sensitivity for GH deficiency (peak GH cut-points: 1.5, 1.4 and 0.64 microg/liter, respectively). However, 95% specificity could be achieved with the ARG plus L-DOPA and ARG tests only with very low peak GH cut-points (0.25 and 0.21 microg/liter, respectively) and not at all with the L-DOPA test. Although serum IGF-I levels provided less diagnostic discrimination than all five GH stimulation tests, a value below 77.2 microg/liter was 95% specific for GH deficiency. In conclusion, the diagnosis of adult GH deficiency can be made without performing an ITT, provided that test-specific cut-points are used. The ARG plus GHRH test represents an excellent alternative to the ITT for the diagnosis of GH deficiency in adults.

Growth hormone release after glucagon as a reliable test of growth hormone assessment in adults

OBJECTIVE

To investigate the GH response to glucagon in adult patients with GH deficiency and in controls compared with the GH response to the insulin tolerance test (ITT) in patients with GH deficiency and to determine whether the use of glucagon results in a diagnostic utility test.

PATIENTS AND DESIGN

Seventy-three patients with adult GH deficiency and organic hypothalamic-pituitary disease were recruited, along with 46 controls. The patients were divided into five groups according to the number of associated hormone deficiencies present.

MEASUREMENTS

Hypopituitary subjects underwent assessment of GH secretory status by the ITT, the glucagon test and measurement of serum IGF-I concentration. Controls underwent the glucagon test. After the ITT, glucose and GH levels were measured at baseline, 30, 60 and 90 minutes, and after glucagon at baseline, 90, 120, 150, 180, 210 and 240 minutes.

RESULTS

The highest GH value after the ITT in the patient group was 3 microg/l (0.76 +/- 0.82 microg/l), and after the glucagon test the highest GH peak value was 2.9 microg/l (0.64 +/- 0.79 microg/l). A correlation was found between the GH peak and the progressive number of hormone deficiencies. After the glucagon test, the GH peak obtained in the controls at 180 minutes was 9.8 +/- 4.6 microg/l and, on an individual basis, none of the 46 controls failed to achieve peak GH levels higher than 3 microg/l. In the controls, a negative correlation was observed between the GH response to glucagon and age (r = -0.389, P = 0.0075) and body mass index (r = -0.329, P = 0.0254). The accuracy of the glucagon test for differentiating patients from controls, estimated by receiver operating characteristics (ROC) curve methodology, showed that the cut-off of 3 microg/l for the GH peak provides 100% sensitivity and 100% specificity and is a reliable decision threshold.

CONCLUSIONS

The glucagon GH test is reliable and provides a clear separation between GH-deficient and normal adults. A single glucagon test with a cut-off of 3 microg/l for the GH peak is diagnostic of GH deficiency in adults and could be considered and studied as an alternative to the ITT.

Diagnosis and management of growth hormone deficiency in adults

In adults, GHD is a clinical syndrome that occurs in patients with pituitary or hypothalamic disease. It may be asymptomatic or present with relatively nonspecific constitutional symptoms. Most patients have abnormal body composition, consisting of increased fat mass and decreased lean mass. Life expectancy is significantly decreased in hypopituitary patients with GHD, with cardiovascular disease a common cause of death. Treatment with growth hormone reverses abnormalities in body composition and may reduce cardiovascular risk factors; however, the long-term treatment outcomes regarding mortality, the incidence of cardiovascular disease, bone fractures, tumor development, and recurrence are not known. Longer prospective clinical studies are needed. The major manufacturers of growth hormone have initiated postmarketing surveillance databases to monitor the safety of growth hormone treatment.

Growth hormone therapy in adults

The importance of growth hormone (GH) deficiency in adults became evident 10 to 15 years ago, when the first clinical studies on GH replacement therapy in adults were published. Since then, a number of studies have been reported showing that GH replacement therapy can improve this condition. Adult GH deficiency (GHD) is now recognized as a specific clinical syndrome and the first reports of long-term use of GH (up to 10 years) are now being published. The aim of this paper was to review the accumulated data on the various clinical aspects of adult GHD.

Níveis séricos de hormônio de crescimento, fator de crescimento símile à insulina e sulfato de deidroepiandrosterona em idosos residentes na comunidade. Correlação com parâmetros clínicos

O envelhecimento é acompanhado de alterações orgânicas possivelmente relacionadas com o sistema endócrino. O eixo GH/IGF-1 e a produção de SDHEA declinam com a idade, caracterizando uma redução de suas atividades, que podem resultar em efeitos deletérios sobre a composição corporal, o sistema cardiovascular e a cognição. Avaliamos a concentração sérica basal de GH, IGF-1 e SDHEA em 225 idosos de uma comunidade (148 mulheres e 77 homens, 70 a 91 anos), 80% deles com características de envelhecimento bem sucedido (Mini-mental > ou = 24 e comprometimento de atividades de vida diária <=3). Tanto o IMC como a pressão arterial estavam significativamente mais elevados nas mulheres. Os níveis de GH também eram maiores nas mulheres (1,6±1,7 vs. 1,0±1,3ng/ml, X±DP, p<0,001), estando acima da faixa de referência em 14% e 19% das mulheres e homens. Já os níveis de IGF-1 eram semelhantes (90±42 e 101±40ng/ml, NS), não sendo elevados em nenhum deles e reduzidos em 35% e 24%, respectivamente. Os níveis de SDHEA eram maiores nos homens (86±58 e 54±36µg/dl, p<0,001), porém na faixa de referência em 92% deles. Houve uma surpreendente correlação positiva entre idade e GH nos homens (r= 0,38, p<0,005), mas uma correlação negativa entre IGF-1 e idade nos dois grupos (r= -0,24 e r= -0,32). Nas mulheres, houve também uma correlação positiva entre SDHEA e IGF-1 (r= 0,27). Em conclusão, níveis basais de GH podem estar elevados em uma parcela significativa dos idosos, sendo maiores nas mulheres, enquanto os níveis de IGF-1 encontram-se normais ou baixos nos dois grupos, sugerindo quadro de resistência hormonal. Os níveis de SDHEA encontravam-se na faixa de referência, sendo maiores nos homens, caracterizando a perda da contribuição ovariana. Diferentemente do que se tem especulado, não encontramos correlação entre os níveis de SDHEA e qualquer parâmetro clínico investigado.