Update on the diagnosis of GH deficiency in adults

The robustness of diagnostic tests for GH deficiency in adults

Since the 1970s, GH treatment has been an important tool in paediatric endocrinology for the management of growth retardation. It is now accepted that adults with severe GH deficiency (GHD) demonstrate impaired physical and psychological well-being and may benefit from replacement therapy with recombinant human GH. There is, however, an ongoing debate on how to diagnose GHD, especially in adults. A GH response below the cut-off limit of a GH-stimulation test is required in most cases for establishing GHD in adults. No 'gold standard' GH-stimulation test exists, but some GH stimulation tests may be more robust to variations in patient characteristics such as age and gender, as well as to pre-test conditions like heat exposure due to a hot bath or bicycling. However, body mass index (BMI) is negatively associated with GH-responses to all available GH-stimulation tests and glucocorticoid treatment, including conventional substitution therapy, influences the GH-responses. Recently, the role of IGF-I measurements in the clinical decision making has been discussed. The aim of this review is to discuss the available GH-stimulation tests. In this author's opinion, tests which include growth-hormone-releasing hormone (GHRH) tend to be more potent and robust, especially the GHRH+arginine test which has been proven to be of clinical use. In contrast, the insulin tolerance test (ITT) and the glucagon test appear to have too many drawbacks.

Low and Normal IGF-1 Levels in Patients with Chronic Medical Disorders (CMD) is Independent of Anterior Pituitary Hormone Deficiencies: Implications for Treating IGF-1 Abnormal Deficiencies with CMD

Over time, based on evidence-based medicine, a number of hormonal test levels including IGF-1 had been raised or lowered to meet new criteria standards. In particular, IGF-1 plasma levels have been shown in several studies to be an independent diagnostic tool in Adult Growth Hormone Deficiency (AGHD). Many endocrinology studies link low IGF-1 plasma levels with low levels of other anterior pituitary hormones (i.e., LH, FSH, and TSH). Low IGF-1 is considered by most to be between 84-100 µ/l and numerous studies recommend that raising IGF-1 to high normal range reverses Chronic Medical Diseases (CMD), improves bone mineral density (BMD), and fibromyalgia. Moreover, some studies suggest that low levels of IGF-1 by itself independent of anterior pituitary deficiencies is sufficient to determine AGHD in humans. In order to determine the relationship of low IGF-1 with that of LH, FSH, and TSH levels in subjects with CMD, we evaluated these levels (± SD) in 944 patients. Patients with IGF-1 below 84 µ/l, 100 µ/l, and 150 µ/l were accessed. 9.22% had less than 84 µ/l (SD ± 12.52); 19.9% had less than 100 µ/l (SD ± 9.54); and 51.6 had less than 150 µ/l (SD ± 26.0). Specifically, the percentages found for low LH, FSH, and TSH were only 4.2%, 4.8%, and 6.5%. We conclude that IGF-1 deficiencies occur independent of comorbid deficiencies of LH, FSH, and TSH. Finally, we propose that based on the present investigation, IGF-1 low levels between the range of 84-100 µ/l may be too low to be considered as an independent diagnostic marker to treat AGHD with CMD.

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.

Growth hormone and selective attention: a review

INTRODUCTION

The relation between growth hormone (GH) secretion and general cognitive function has been established. General cognitive functioning depends on core functions including selective attention, which have not been addressed specifically in relation to GH. The present review addresses current insights about specific effects of growth hormone deficiency (GHD) on varieties of selective attention, as well as effects of GH suppletion.

MATERIALS AND METHODS

Studies investigating relationships between GH status and valid measures of selective or divided attention were reviewed.

RESULTS AND DISCUSSION

There are no indications that GHD is characterized by impaired attribute selection, interference control, or attentional switching. In contrast, a few studies point to a deficit in integrated processing of multiple dimensions, as well as speed of information processing. There is also weak evidence for beneficial effects of GH replacement in the opposite direction in these domains.

CONCLUSIONS

The function of integrated processing of multiple stimulus dimensions may be based on neural mechanisms in the anterior cingulate cortex and its extensive connections to the hippocampus, the latter being known to be rich in GH receptors.

The chronic oral administration of arginine aspartate decreases secretion of IGF-1 and IGFBP-3 in healthy volunteers

To investigate the effect of chronic oral arginine aspartate on the growth hormone (GH), GH-releasing hormone (GHRH), insulin-like growth factor-1 (IGF-1) and IGF-binding protein-3 (IGFBP-3) secretions in healthy volunteers. Twenty-three healthy non-athlete volunteer males were administered arginine aspartate (30 g) orally once daily at 21:00 h for 21 consecutive days. Subjects were hospitalized on days 0, 1, 3, 5, 7, 14 and 21 of treatment. At each hospitalization, concentrations of GHRH, GH, IGF-1 and IGFBP-3 were measured over 4 h after arginine aspartate intake. GH, IGF-1 and IGFBP-3 concentrations were also determined over 12 h at days 0, 1 and 21. Compared with day 1, 4 h GH levels dropped at day 5 and subsequently rose to levels not significantly different from initial ones. The latter was substantiated by 12 h GH levels that did not significantly change from days 1 to 21. GHRH levels were not statistically different, although there was a trend in median values that seemed to inversely mirror those of GH. This dynamic over the course of the study for GH and GHRH was accompanied by a general decrease in IGF-1 and IGFBP-3. In healthy volunteers, a chronic oral treatment with 30 g/day arginine aspartate is followed by a decrease in IGF-1 and IGFBP-3 secretions.

Growth hormone replacement throughout life: insights into age-related responses to treatment

The adult growth hormone deficiency (GHD) syndrome is a well-defined clinical entity. Although the symptoms of GHD are not age specific, their relative importance differs depending on the patient's age, and the impact of GHD varies throughout adult life. Ceasing growth hormone (GH) therapy soon after final height in patients with severe GHD potentially limits somatic development by reducing accrual of bone and muscle mass. It is now recognized that the continuation of GH therapy in the transition years is required to achieve adult levels of somatic development. In middle age, the most worrying feature of GHD is the increase in cardiovascular risk, an important component of which is GHD-related dyslipidemia. One of the most profound effects of GH therapy in this age group is the durable reduction in cholesterol levels. Elderly GH-deficient patients experience the symptoms of GHD over and above the signs of normal aging. Perhaps most importantly, these patients have impaired quality of life, with fatigue as a major component. Evidence is growing for improved quality of life with GH therapy in the elderly. This review describes the diagnosis, symptoms and treatment of GHD specific to the different age groups.

Oral and maxillofacial manifestations of Gardner's syndrome associated with growth hormone deficiency: case report and literature review

Gardner's syndrome (GS) is a hereditary disorder inherited as autosomal dominant with complete penetrance and variable expression. GS is a variant of familial adenomatous polyposis characterized by extracolonic manifestations including osteomas, dental anomalies, and epidermoid cysts. The association between GS and endocrine abnormalities has been well documented but a direct pituitary involvement has never been reported. We present a case of oral and maxillofacial manifestations in an adult patient affected by GS associated with growth hormone deficiency, a hitherto unreported association. The possible pathogenic mechanisms are discussed.

Growth hormone levels in the diagnosis of growth hormone deficiency in adulthood

Current guidelines for the diagnosis of adult growth hormone deficiency (GHD) state that the diagnosis must be proven biochemically by provocative testing that is done within the appropriate clinical context. The need for reliance on provocative testing is based on evidence that the evaluation of spontaneous growth hormone (GH) secretion over 24 h and the measurement of IGF-I and IGFBP-3 levels do not distinguish between normal and GHD subjects. Regarding IGF-I, it has been demonstrated that very low levels in patients highly suspected for GHD (i.e., patients with childhood-onset, severe GHD, or with multiple hypopituitarism acquired in adulthood) may be considered definitive evidence for severe GHD obviating the need for provocative tests. However, normal IGF-I levels do not rule out severe GHD and therefore adults suspected for GHD and with normal IGF-I levels must undergo a provocative test of GH secretion. The insulin tolerance test (ITT) is the test of choice, with severe GHD being defined by a GH peak less than 3 microg/l, the cut-off that distinguishes normal from GHD adults. The ITT is contraindicated in the presence of ischemic heart disease, seizure disorders, and in the elderly. Other tests are as reliable as the ITT, provided they are used with appropriate cut-off limits. Glucagon stimulation, a classical test, and especially new maximal tests such as GHRH in combination with arginine or GHS (i.e., GHRP-6) have well-defined cut-off limits, are reproducible, are independent of age and gender, and are able to distinguish between normal and GHD subjects. The confounding effect of overweight or obesity on the interpretation of the GH response to provocative tests needs to be considered as the somatotropic response to all stimuli is negatively correlated with body mass index. Appropriate cut-offs for lean, overweight, and obese subjects must be used in order to avoid false-positive diagnoses of severe GHD in obese adults.

Anterior pituitary hormone replacement therapy--a clinical review

This clinical review summarizes current approaches to diagnosis and treatment of anterior pituitary hormone deficiency. The diagnostic value of endocrine function tests and replacement strategies for hydrocortisone, thyroxine, sex steroids, and growth hormone replacement are reviewed. Female androgen deficiency syndrome and the current role of DHEA and testosterone replacement in women are also discussed.

Approach to the evaluation of the GH/IGF-axis in patients with pituitary disease: which test to order

The diagnosis of adult growth hormone deficiency (AGHD) and acromegaly involves assessment of serum growth hormone (GH) and insulin-like growth factor-1 (IGF-1) concentrations. The diagnosis of AGHD typically requires a provocative test of GH reserve, but is supported by demonstration of low-serum IGF-1 levels. Therapeutic monitoring of rhGH replacement is performed utilizing measurement of serum IGF-1 concentrations. In patients with suspected acromegaly, the diagnosis is confirmed by elevated serum IGF-1 levels and further validated by the presence of elevated GH levels both before and following an oral glucose load. A goal of acromegaly therapy is to normalize IGF-1 concentrations, and, depending on the therapeutic modality, GH levels as well. Using case based clinical scenarios, we have presented a standard approach to the biochemical diagnosis and therapeutic monitoring of these disorders.

Role of endogenous ghrelin in growth hormone secretion, appetite regulation and metabolism

Ghrelin, a 28-amino acid hormone that is acylated post-translation, is the endogenous ligand for the growth hormone (GH) secretagogue (GHS) receptor (GHS-R). The highest concentrations of ghrelin are found in the stomach; however ghrelin peptide is also present in hypothalamic nuclei known to be important in the control of GH and feeding behavior. Exogenous ghrelin potently stimulates pituitary GH release through a mechanism that is dependent, in part, on endogenous GH-releasing hormone. Whether endogenous ghrelin plays a role in the control of GH secretion and growth is not clear and ghrelin deficient animals appear to grow normally. In contrast, experimental animal and clinical data suggest that abnormalities in GHS-R signaling could impact growth. Ghrelin or other GHS are clinically useful for GH-testing and limited data suggest that they might be useful in the treatment of some patients with GH deficiency. Substantial data have implicated ghrelin as an important regulator of feeding behavior and energy equilibrium. Ghrelin has a potent orexigenic effect in both animals and humans and this effect is mediated through hypothalamic neuropeptide Y (NPY) and Agouti-related peptide (AgRP). Appetite simulation coupled with other metabolic effects promotes weight gain during chronic treatment with ghrelin. These metabolic effects are in part mediated through an increase in respiratory quotient (VQ). Presence of ghrelin appears to be necessary for the development of obesity in some animal models. Whether abnormalities in ghrelin signaling are involved in human obesity is not yet known.

Growth hormone and its disorders

Growth hormone (GH) is synthesised and secreted by the somatotroph cells of the anterior lobe of the pituitary gland. Its actions involve multiple organs and systems, affecting postnatal longitudinal growth as well as protein, lipid, and carbohydrate metabolism. GH hypersecretion results in gigantism or acromegaly, a condition associated with significant morbidity and mortality, while GH deficiency results in growth retardation in children and the GH deficiency syndrome in adults. This article, aimed at non-paediatric physicians, examines the clinical features, diagnosis, and current concepts in the management of these conditions.

Evaluation of pituitary function in the fatigued patient: a review of 59 cases

OBJECTIVE

The aim of this study was to review the results of dynamic pituitary testing in patients presenting with fatigue.

METHODS

We reviewed clinical histories and insulin tolerance test (ITT) results of 59 patients who presented with fatigue and other symptoms of glucocorticoid insufficiency over a 4-year period. All patients referred for ITT had an early-morning cortisol level of <400 nM and a low or normal ACTH level.

RESULTS

Peak cortisol and GH responses following insulin-induced hypoglycaemia were normal in only seven patients (12%). Median age of the remaining 52 patients was 47 years (range, 17-67 years); all but five were female. Common presenting symptoms were neuroglycopaenia (n = 47), depression (n = 37), arthralgia and myalgia (n = 28), weight gain (n = 25), weight loss (n = 9), postural dizziness (n = 15) and headaches (n = 13). Other medical history included autoimmune disease (n = 20; particularly Hashimoto's thyroiditis, Graves' disease and coeliac disease), postpartum (n = 8) and gastrointestinal (n = 2) haemorrhage and hyperprolactinaemia (n = 13). 31 subjects had peak cortisol levels of <500 nM (suggestive of ACTH deficiency; 18 of whom had levels < 400 nM) and a further six had indeterminate results (500-550 nM). The remaining 15 subjects had normal cortisol responses (median 654 nM; range, 553-1062 nM) but had low GH levels following hypoglycaemic stimulation (5.9 mU/l; 3-11.6 mU/l).

CONCLUSION

Our results suggest that patients presenting with fatigue and symptoms suggestive of hypocortisolism should be considered for screening for secondary adrenal insufficiency, particularly in the presence of autoimmune disease or a history of postpartum or gastrointestinal haemorrhage. Whether physiological glucocorticoid replacement improves symptoms in this patient group is yet to be established.

The cut-off limits of the GH response to GH-releasing hormone-arginine test related to body mass index

OBJECTIVE

The diagnosis of growth hormone (GH) deficiency (GHD) in adults is based on a reduced peak GH response to provocative tests, such as the insulin tolerance test (ITT) and the GH-releasing hormone-arginine (GHRH-ARG) test. However, the cut-off limits of peak GH response in lean subjects are not reliable in obese patients; this is noteworthy since adult GHD is often associated with obesity. Aim of this study was to evaluate the diagnostic cut-off limits of peak GH response to the GHRH-ARG test in overweight and obese as well as in lean population.

DESIGN AND METHODS

The GH responses to the GHRH-ARG test were studied in 322 patients with organic hypothalamic-pituitary disease and in 318 control subjects. Patients were subdivided into two groups on the basis of the number of pituitary hormone deficits, except for GH deficiency: (a) patients with total pituitary hormone deficit (TPHD) and (b) patients without or with no more than two pituitary hormone deficits (PHD). Both patients and control subjects were divided into three subgroups according to body mass index (BMI): lean (BMI <25 kg/m(2)), overweight (BMI > or = 25 and <30 kg/m(2)) and obese (BMI > or =30 kg/m(2)). TPHD patients were assumed to be GH deficient, whereas PHD patients may include subjects with either normal or impaired GH secretion. The statistical analysis was carried out by the Receiver-Operating Characteristic curve analysis (Medcalc 7.2). The diagnostic cut-off points were calculated for lean, overweight and obese subjects to provide optimal separation of GH-deficient patients and control subjects according to two criteria: (1) a balance between high sensitivity and high specificity; (2) to provide the highest pair of sensitivity/specificity values for GH deficiency.

RESULTS

In the lean population the best pair of values, with highest sensitivity as 98.7% and highest specificity as 83.7%, was found using a peak GH cut-off point of 11.5 mug/l. In the overweight population the best pair of values, 96.7 and 75.5%, respectively, was found using a peak GH cut-off point of 8.0 mug/l. In the obese population the best pair of values, 93.5 and 78.3%, respectively, was found using a peak GH cut-off point of 4.2 mug/l. Applying the above mentioned cut-off points, among PHD patients we found that 80 subjects (72%) were GHD whereas 31 (28%) had normal GH secretion.

CONCLUSIONS

In conclusion the GHRH-ARG test is a reliable tool for the diagnosis of adult GH deficiency in lean, overweight and obese patients, provided that specific BMI-related cut-off limits are assumed.

Hypopituitarism after traumatic brain injury

Traumatic brain injury (TBI) is one of the main causes of death and disability in young adults, with consequences ranging from physical disabilities to long-term cognitive, behavioural, psychological and social defects. Post-traumatic hypopituitarism (PTHP) was recognized more than 80 years ago, but it was thought to be a rare occurrence. Recently, clinical evidence has demonstrated that TBI may frequently cause hypothalamic-pituitary dysfunction, probably contributing to a delayed or hampered recovery from TBI. Changes in pituitary hormone secretion may be observed during the acute phase post-TBI, representing part of the acute adaptive response to the injury. Moreover, diminished pituitary hormone secretion, caused by damage to the pituitary and/or hypothalamus, may occur at any time after TBI. PTHP is observed in about 40% of patients with a history of TBI, presenting as an isolated deficiency in most cases, and more rarely as complete pituitary failure. The most common alterations appear to be gonadotropin and somatotropin deficiency, followed by corticotropin and thyrotropin deficiency. Hyper- or hypoprolactinemia may also be present. Diabetes insipidus may be frequent in the early, acute phase post-TBI, but it is rarely permanent. Severity of TBI seems to be an important risk factor for developing PTHP; however, PTHP can also manifest after mild TBI. Accurate evaluation and long-term follow-up of all TBI patients are necessary in order to detect the occurrence of PTHP, regardless of clinical evidence for pituitary dysfunction. In order to improve outcome and quality of life of TBI patients, an adequate replacement therapy is of paramount importance.

Comparison of adrenal function tests in children--the glucagon stimulation test allows the simultaneous assessment of adrenal function and growth hormone response in children

The accurate assessment of adrenal function is necessary in many children with suspicion of pituitary insufficiency. The objective of this study was to evaluate the adrenal response during the glucagon stimulation test (GST) and its diagnostic utility in children. A total of 290 children, aged 10.1 +/- 5.0 years, were evaluated for adrenal function using the corticotrophin releasing hormone (CRH) test, the GST, and/or the insulin tolerance test (ITT). Glucagon stimulation provoked a substantial rise in cortisol and adrenocorticotropin (ACTH) that was independent of gender, age, or underlying growth hormone deficiency. There were no differences in peak cortisol levels in the GST compared to the CRH test in pair-wise intra-individual analyses in children with both tests performed within one year (615.4 +/- 30.5 vs 602.8 +/- 22.4 nmol/l, n=52). Similarly, there were no differences in the cortisol response between the ITT and CRH test. Peak cortisol levels in the CRH test correlated with the GST and the ITT. The magnitude of ACTH response, in contrast, was highest in the ITT with a 9.8-fold increase over baseline, while the increase in the GST (3.1-fold) and CRH test (1.6-fold) were more subtle. Since there is controversy concerning reliable cut-off values for adrenal function tests in children, we analyzed cut off levels in 186 children, including 26 children with adrenal insufficiency, using the CRH test. A peak cortisol level of 450 nmol/l provided the best balance of sensitivity (88.5%) and specificity (86.8%), while higher cut-off levels did not increase sensitivity but lost in specificity. In summary, the GST constitutes an1 equally sensitive test for the assessment of adrenal function in children that is not confounded by anthropometric parameters and is generally not accompanied by major side effects. It allows the simultaneous assessment of corticotroph and somatotroph function and may thus constitute a valuable alternative to the ITT.

Insulin-Like Growth Factor I Levels and the Diagnosis of Adult Growth Hormone Deficiency

The current guidelines state that, within the appropriate clinical context, the diagnosis of adult growth hormone (GH) deficiency must be made biochemically using provocative tests. Measurement of insulin-like growth factor I (IGF-I) and binding protein 3 (IGFBP-3) levels cannot always distinguish between healthy and GH-deficient individuals. In particular, IGFBP-3 as a marker of GH status is clearly less sensitive than IGF-I and there is general agreement that its measurement does not provide useful diagnostic information. However, the diagnostic value of measuring IGF-I levels has been revisited recently. It has been confirmed that normal IGF-I levels do not rule out severe GH deficiency (GHD) in adults, in whom the diagnosis has therefore to be based on the demonstration of severe impairment of the peak GH response to provocative tests. It has also been emphasized that very low IGF-I levels in patients with high suspicion of GHD could be considered to be definite evidence for severe GHD. This assumption particularly applies to patients with childhood-onset, severe GHD or with multiple hypopituitary deficiencies acquired in adulthood. In addition, the use of IGF-I levels to monitor the efficacy and adequacy of recombinant human GH replacement remains widely accepted.