Evaluation of acromegaly by radioimmunoassay of somatomedin-C

IGF-I assay methods and biologic variability: evaluation of acromegaly treatment response

Serum insulin-like growth factor (IGF-I) is the primary biochemical measure of disease activity in patients with acromegaly, and the 2014 Endocrine Society guidelines recommended normal age-adjusted serum IGF-I as the biochemical target of treatment. However, quantification and interpretation of IGF-I levels are subject to limitations that may affect therapeutic decisions. Techniques for measuring IGF-I have evolved greatly over the past 40 years and continue to do so. Results can vary substantially for different assays, procedures, and laboratories. For any assay, the interpretation of IGF-I values requires robust reference ranges. Using currently available large normative databases, the upper limit of normal (ULN) for IGF-I in middle-aged and elderly individuals is lower than historical reference ranges. Thus, the goal of achieving IGF-I < 1× ULN is more demanding than in the past, and some patients with acromegaly who were classified as "normal" (IGF-I < 1× ULN) in previous studies would be reclassified as above the ULN based on newer normative data. In addition, substantial intra-individual, week-to-week variation in serum IGF-I levels (unrelated to assay performance) has been observed. With changes over time in the measurement of IGF-I and the advent of updated reference ranges derived from large normative databases, it is difficult to justify rigid adherence to the goal of maintaining IGF-I below the ULN for all patients with acromegaly. Instead, symptoms, comorbidities, and quality of life should be considered, along with growth hormone and IGF-I levels, when evaluating the need for further treatment.

Challenges of insulin-like growth factor-1 testing

Insulin-like growth factor 1 (IGF-1), primarily synthesized in the liver, was initially discovered due to its capacity to replicate the metabolic effects of insulin. Subsequently, it emerged as a key regulator of the actions of growth hormone (GH), managing critical processes like cell proliferation, differentiation, and apoptosis. Notably, IGF-1 displays a longer half-life compared to GH, making it less susceptible to factors that may affect GH concentrations. Consequently, the measurement of IGF-1 proves to be more specific and sensitive when diagnosing conditions such as acromegaly or GH deficiency. The recognition of the existence of IGFBPs and their potential to interfere with IGF-1 immunoassays urged the implementation of various techniques to moderate this issue and provide accurate IGF-1 results. Additionally, in response to the limitations associated with IGF-1 immunoassays and the occurrence of discordant IGF-1 results, modern mass spectrometric methods were developed to facilitate the quantification of IGF-1 levels. Taking advantage of their ability to minimize the interference caused by IGF-1 variants, mass spectrometric methods offer the capacity to deliver robust, reliable, and accurate IGF-1 results, relying on the precision of mass measurements. This also enables the potential detection of pathogenic mutations through protein sequence analysis. However, despite the analytical challenges, the discordance in IGF-1 reference intervals can be attributed to a multitude of factors, potentially leading to distinct interpretations of results. The establishment of reference intervals for each assay is a demanding task, and it requires nationwide multicenter collaboration among laboratorians, clinicians, and assay manufacturers to achieve this common goal in a cost-effective and resource-efficient manner. In this comprehensive review, we examine the challenges associated with the standardization of IGF-1 measurement methods, the minimization of pre-analytical factors, and the harmonization of reference intervals. Particular emphasis will be placed on the development of IGF-1 measurement techniques using "top-down" or "bottom-up" mass spectrometric methods.

Interpreting growth hormone and IGF-I results using modern assays and reference ranges for the monitoring of treatment effectiveness in acromegaly

Standard treatment for acromegaly focuses on the achievement of target absolute levels of growth hormone (GH) and insulin-like growth factor (IGF-I). The appropriateness of these targets when measured using modern assay methods is not well defined. This paper reviews biochemical status assessed using methods available at the time and associated clinical outcomes. GH measurements were shown to provide an indication of changes in tumor size, and failure of GH suppression after glucose stimulation is associated with tumor recurrence. IGF-I levels were more closely associated with changes in symptoms and signs. Reduced GH and IGF-I concentrations were shown to be associated with increased longevity, although the degree of increase has only been analyzed for GH. Lowering of GH and IGF-I has consistently been associated with improved outcomes; however, absolute levels reported in previous studies were based on results from methods and reference ranges that are now obsolete. Applying previously described absolute thresholds as targets (e.g. "normal" IGF-I level) when using current methods is best applied to those with active acromegaly symptoms who could benefit from further lowering of biochemical markers. In asymptomatic individuals with mild IGF-I or GH elevations, targeting biochemical "normalization" would result in the need for combination pharmacotherapy in many patients without proven benefit. Measurement of both GH and IGF-I remains an essential component of diagnosis and monitoring the effectiveness of treatment in acromegaly; however, treatment goals based only on previously identified absolute thresholds are not appropriate without taking into account the assay and reference ranges being employed. Treatment goals should be individualized considering biochemical improvement from an untreated baseline, symptoms of disease, risks, burdens and costs of complex treatment regimens, comorbidities, and quality of life.

Interaction of a viral insulin-like peptide with the IGF-1 receptor produces a natural antagonist

Lymphocystis disease virus-1 (LCDV-1) and several other Iridoviridae encode viral insulin/IGF-1 like peptides (VILPs) with high homology to human insulin and IGFs. Here we show that while single-chain (sc) and double-chain (dc) LCDV1-VILPs have very low affinity for the insulin receptor, scLCDV1-VILP has high affinity for IGF1R where it can antagonize human IGF-1 signaling, without altering insulin signaling. Consequently, scLCDV1-VILP inhibits IGF-1 induced cell proliferation and growth hormone/IGF-1 induced growth of mice in vivo. Cryo-electron microscopy reveals that scLCDV1-VILP engages IGF1R in a unique manner, inducing changes in IGF1R conformation that led to separation, rather than juxtaposition, of the transmembrane segments and hence inactivation of the receptor. Thus, scLCDV1-VILP is a natural peptide with specific antagonist properties on IGF1R signaling and may provide a new tool to guide development of hormonal analogues to treat cancers or metabolic disorders sensitive to IGF-1 without affecting glucose metabolism.

Outcomes in pituitary adenoma causing acromegaly following endoscopic endonasal transsphenoidal surgery

Objectives

The objectives of the study were to study the analysis of outcomes after endoscopic endonasal transsphenoidal surgery (EETSS) in acromegaly in terms of surgical complications, clinical improvement, endocrinological remission, achievement of prognostically critical growth hormone (GH) level, and requirement of additional treatment.

Materials and Methods

The study included 28 acromegaly patients, who underwent EETSS. A 2010 consensus criterion was used for defining remission. Assessment of prognostically critical GH level (random value <2.5 ng/ml), the extent of resection and additional treatment, was done at post-operative week (POW) 12.

Results

All adenomas were macroadenomas; with a mean volume of 16.34 cm3 (range, 0.4-99 cm3). Most adenomas had high-grade extensions. Most common suprasellar, infrasellar, anterior, and posterior extension grades were 3 (n = 13), 1 (n = 16), 1 (n = 14), and 0 (n = 20), respectively. Knosp Grade 3 was common on both sides (right, n = 9 and left, n = 8). One patient had already been operated on with EETSS, 1.5 years back from current surgery. Sixteen patients were on hormonal support, preoperatively. Four patients died during follow-up. Post-operative common complications were diabetes insipidus (DI, n = 18), cerebrospinal fluid rhinorrhea (n = 10), surgical site hematoma (n = 3), meningitis (n = 3), hydrocephalus (n = 2), and syndrome of inappropriate antidiuretic hormone (n = 1). The mean hospital stay was 11.62 days and 12.17 months were the mean follow-up period. At 12 POW, no improvement was seen in body enlargement and visual complaints, but all other complaints improved significantly except perspiration. Adenomas were decreased in all extensions except posterior and mean adenoma volume was reduced from 16.34 cm3 to 2.92 cm3 after surgery. Sub-total resection (STR, n = 10), near-total resection (NTR, n = 7), gross-total resection (GTR, n = 5), and partial resection (PR, n = 2) were achieved. Endocrinological remission and prognostically critical GH levels were attained in 29.17% (n = 7) and 66.67% (n = 16), respectively. NTR, GTR, STR, and PR were associated with 57.14%, 40%, 10%, and 0% endocrinological remission, respectively. Additional treatment was required in a total of 17 patients, three in GTR, nine in STR, three in NTR, and two in PR. Ten were treated with Gamma Knife radiosurgery along with medical treatment and seven with medical treatment alone.

Conclusion

A successful EETSS can reduce adenoma volume to achieve clinical improvement, endocrinologic remission, and prognostically critical GH level with some complications related to surgery. Pre-operative larger volume and higher extension grades affect these outcomes adversely.

Outcomes in Pituitary Adenoma Causing Acromegaly Following Endoscopic Endonasal Transsphenoidal Surgery

Objectives The objective of this study was the analysis of outcomes after endoscopic endonasal transsphenoidal surgery (EETSS) in acromegaly in terms of surgical complications, clinical improvement, endocrinological remission, achievement of prognostically critical growth hormone (GH) level, and requirement of additional treatment.

Materials and Methods The study included 28 acromegaly patients, who underwent EETSS. 2010 consensus criterion was used for defining remission. Assessment of prognostically critical GH level (random value less than 2.5 ng/mL), the extent of resection, and additional treatment was done at postoperative week (POW) 12.

Results All adenomas were macroadenomas, with the mean volume of 16.34 cm3 (range, 0.4–99 cm3). Most adenomas had high-grade extensions. Most common suprasellar, infrasellar, anterior, and posterior extension grades were 3 (n = 13), 1(n = 16), 1(n = 14), and 0 (n = 20), respectively. Knosp grade 3 was common on both sides (right, n = 9 and left, n = 8). One patient had already been operated on with EETSS, 1.5 years back from current surgery. Sixteen patients were on hormonal support, preoperatively. Four patients died during follow-up. Postoperative common complications were diabetes insipidus (n = 18), cerebrospinal fluid rhinorrhea (n = 10), surgical site hematoma (n = 3), meningitis (n = 3), hydrocephalus (n = 2), and syndrome of inappropriate antidiuretic hormone (n = 1). The mean hospital stay was 11.62 days, and 12.17 months was the mean follow-up period. At 12 POW, no improvement was seen in body enlargement and visual complaints, but all other complaints improved significantly except perspiration. Adenomas were decreased in all extensions except posterior, and mean adenoma volume was reduced from 16.34 to 2.92 cm3 after surgery. Subtotal resection (STR, n = 10), near-total resection (NTR, n = 7), gross-total resection (GTR, n = 5), and partial resection (PR, n = 2) were achieved. Endocrinological remission and prognostically critical GH levels were attained in 29.17% (n = 7) and 66.67% (n = 16), respectively. NTR, GTR, STR, and PR were associated with 57.14, 40, 10, and 0% endocrinological remission, respectively. Additional treatment was required in a total of 17 patients: 3 GTR, 9 STR, 3 NTR, and 2 PR patients. Ten patients were treated with gamma knife radiosurgery along with medical treatment and seven with medical treatment alone.

Conclusion A successful EETSS can reduce adenoma volume to achieve clinical improvement, endocrinological remission, and prognostically critical GH level with some complications related to surgery. Preoperative larger volume and higher extension grades affect these outcomes adversely.

Insulin-Like Growth Factor 1 in the Early Postoperative Assessment of Acromegaly

OBJECTIVES

Assessment of surgical outcome in acromegaly is typically recommended at 3 to 6 months following surgery. The purpose of this study was to determine if insulin-like growth factor 1 (IGF-1) concentrations at 6 weeks were equally predictive of surgical outcomes compared with IGF-1 concentrations at 3 to 6 months postoperatively applying newer IGF-1 assays.

METHODS

Retrospective review of patients with newly diagnosed acromegaly who had surgery between 2013 and 2020 and had postoperative IGF-1 measured by 6 weeks and 3 to 6 months.

RESULTS

At 6 weeks, 20 (35%) of the total 57 had normal IGF-1 and became abnormal in 1 at 3 to 6 months, whereas 37 (65%) of 57 had abnormal IGF-1 concentrations at 6 weeks, which normalized in 1 patient by 3 to 6 months. In patients who changed clinical status, IGF-1 at 6 weeks was within ±0.1-fold of normal. Although a difference was seen between median IGF-1 concentrations (286 vs 267 ng/mL, P = .009) at 6 weeks and 3 to 6 months, the mean reduction was small (-19.9 ng/mL).

CONCLUSIONS

Compared with 3 to 6 months, use of IGF-1 at 6 weeks was associated with a change in clinical status in 3.5% of patients. Therefore, in most patients, IGF-1 at 6 weeks can be used to assess clinical outcome via newer assays.

Soluble Alpha Klotho in Acromegaly: Comparison With Traditional Markers of Disease Activity

CONTEXT

Soluble alpha klotho (sαKL) has been linked to growth hormone (GH) action, but systematic evaluation and comparisons with traditional biomarkers in acromegaly are lacking.

OBJECTIVE

To evaluate the potential of sαKL to aid classification of disease activity.

METHODS

This retrospective study at 2 academic centers included acromegaly patients before surgery (A, n = 29); after surgery (controlled, discordant, or uncontrolled) without (B1, B2, B3, n = 28, 11, 8); or with somatostatin analogue treatment (C1, C2, C3, n = 17, 11, 5); nonfunctioning pituitary adenomas (n = 20); and healthy controls (n = 31). sαKL was measured by immunoassay and compared with traditional biomarkers (random and nadir GH, insulin-like growth factor I [IGF-I], IGF binding protein 3). Associations with disease activity were assessed.

RESULTS

sαKL was correlated to traditional biomarkers, particularly IGF-I (rs=0.80, P <0.0001). High concentrations before treatment (A, median, interquartile range: 4.04 × upper limit of normal [2.26-8.08]) dropped to normal after treatment in controlled and in most discordant patients. A cutoff of 1548 pg/mL for sαKL discriminated controlled (B1, C1) and uncontrolled (B3, C3) patients with 97.8% (88.4%-99.9%) sensitivity and 100% (77.1%-100%) specificity. sαKL was below the cutoff in 84% of the discordant subjects. In the remaining 16%, elevated sαKL and IGF-I persisted, despite normal random GH. Sex, age, body mass index, and markers of bone and calcium metabolism did not significantly affect sαKL concentrations.

CONCLUSION

Our data support sαKL as a biomarker to assess disease activity in acromegaly. sαKL exhibits close association with GH secretory status, large dynamic range, and robustness toward biological confounders. Its measurement could be helpful particularly when GH and IGF-I provide discrepant information.

Clinical features and therapeutic outcomes of patients with acromegaly in Saudi Arabia: a retrospective analysis

BACKGROUND

Acromegaly is a rare disease resulting in clinical sequelae with significant morbidity and mortality due to the central tumor mass effect and prolonged growth hormone (GH) hypersecretion.

OBJECTIVES

The goal is to describe the epidemiology, clinical features, presence of comorbidities, and treatment outcomes of acromegaly in Saudi Arabia.

METHODS

Data was collected through a retrospective review of the charts of all patients diagnosed with acromegaly from nine major hospitals in Saudi Arabia over a period of more than 25 years.

RESULTS

A total of 195 patients (116 males and 79 females), with a mean age at diagnosis of 43 ± 12 (males) and 46 ± 14 years (females), from nine major hospitals were identified and included in the analysis. All cases were caused by pituitary adenomas, of which 92.4% were macroadenomas. Headache, coarse facial features, acral growth, and sweating/oily skin were by far the most frequent presenting complaints. The most common comorbidities were diabetes mellitus (51.7%), followed by hypertension (50%) and visual field defect (30.5%). The vast majority (95%) of patients were treated surgically (98%). Twenty-four percent also received radiotherapy, and 74.4% received medical therapy. When stringent criteria were applied for assessment of outcomes of therapy, 28.7% of the patients were cured and 30.1% had their disease under control, while 28.7% were found to have active disease despite receiving multimodal therapy.

CONCLUSIONS

Our findings highlight the need for a national acromegaly registry to enable early identification, evaluation, and selection of the best therapeutic approaches to improve the outcome and remission rate of the disease.

Decrease of Serum IGF-I following Transsphenoidal Pituitary Surgery for Acromegaly

BACKGROUND

In the immediate postoperative period following resection of growth hormone (GH)-secreting pituitary tumors, serum concentrations of GH have limited ability to predict remission of acromegaly. Since many actions of GH actions are mediated by insulin-like growth factor-1 (IGF-I), we aimed to determine the rates of fall of IGF-I during 72 h after surgical resection of pituitary tumors.

METHODS

We studied patients who were undergoing pituitary surgery for acromegaly. IGF-I was measured by LC-MS and GH by immunoassay. Remission was defined by the combination of serum GH &lt;0.4 ng/mL during oral glucose tolerance testing performed 8 weeks after the surgical procedure and normal IGF-I at ≥8 weeks.

RESULTS

During the first 72 h after surgery, the mean (SD) rate of decline of IGF-I was 185 (61) ng/mL per 24 h in those who achieved remission (n = 23), with a mean (SD) apparent half-life of 55 (19) h. IGF-I had decreased to &lt;65% of the preoperative IGF-I on postoperative day 2 in 20 of 23 remission patients (87%) vs none of 5 patients who did not achieve remission. GH was &lt;2.7 ng/mL on day 2 in 21 of 23 remission patients (91%), but in none of the nonremission patients. The combination of IGF-I and GH on day 2 separated the remission and nonremission groups of patients.

CONCLUSIONS

Rapid decline of serum IGF-I during the immediate postoperative period warrants further study as an analytically independent adjunct to GH measurement for early prediction of biochemical remission of acromegaly.

"Micromegaly": an update on the prevalence of acromegaly with apparently normal GH secretion in the modern era

PURPOSE

Approximately 25 % of cases of clinically active acromegaly cases treated in our academic center between 1996 and 2000, were diagnosed in patients who had elevated plasma IGF-1 levels, but apparently "normal" 24-h mean plasma GH levels. The current study served to update the data for patients with acromegaly referred to our facility, after increasing awareness of this "normal" GH subpopulation throughout the medical community.

METHODS

A retrospective chart review was conducted on 157 patients with acromegaly who underwent resection of a confirmed somatotroph pituitary adenoma at the University of Michigan Health System between the dates of 1 Jan 2001 to 23 Sept 2015.

RESULTS

Overall prevalence of acromegalic patients with "normal" GH levels, defined as GH <4.7 ng/mL, was 31 %. Over time, the percentage of patients with "normal" GH at diagnosis did not decline: 26 % from 2001 to 2005, 19 % from 2006 to 2010, and 47 % from 2011 to 2015. Mean pituitary tumor size was 1.8 ± 0.1 cm for the group with elevated GH, and 1.2 ± 0.1 cm for the group with "normal" GH (p < 0.001). Percent microadenomas was higher in a group with "normal" GH as compared to those with elevated GH (48 vs. 12 %, p < 0.001), and tumors >2 cm in the maximal diameter were encountered more frequently in the group with elevated GH (43 vs. 14 %, p < 0.001).

CONCLUSIONS

Our data show that a substantial percentage of patients with clinical acromegaly have "normal" GH, and therefore strengthens the growing body of evidence which supports the leading role of IGF-1 levels in diagnostic evaluation. At the present time, questions about the natural course of "micromegaly" and treatment benefits compared to the subpopulation with elevated GH levels remain unanswered, but research continues to build on our understanding of the heterogeneous population of individuals.

Correlation between GH and IGF-1 during treatment for acromegaly

OBJECTIVE The relationship between growth hormone (GH) and insulin-like growth factor-1 (IGF-1) in patients with acromegaly as serial levels drop over time after treatment has not been examined previously. Knowledge of this relationship is important to correlate pretreatment levels that best predict response to treatment. To examine the correlation between GH and IGF-1 and IGF-1 z-scores over a wide range of GH levels, the authors examined serial GH and IGF-1 levels at intervals before and after surgery and radiosurgery for acromegaly. METHODS This retrospective analysis correlates 414 pairs of GH and IGF-1 values in 93 patients with acromegaly. RESULTS Absolute IGF-1 levels increase linearly with GH levels only up to a GH of 4 ng/ml, and with IGF-1 z-scores only to a GH level of 1 ng/ml. Between GH levels of 1 and 10 ng/ml, increases in IGF-1 z-scores relative to changes in GH diminish and then plateau at GH concentrations of about 10 ng/ml. From patient to patient there is a wide range of threshold GH levels beyond which IGF-1 increases are no longer linear, GH levels at which the IGF-1 response plateaus, IGF-1 levels at similar GH values after the IGF-1 response plateaus, and of IGF-1 levels at similar GH levels. CONCLUSIONS In acromegaly, although IGF-1 levels represent a combination of the integrated effects of GH secretion and GH action, the tumor produces GH, not IGF-1. Nonlinearity between GH and IGF-1 occurs at GH levels far below those previously recognized. To monitor tumor activity and tumor viability requires measurement of GH levels.

The Role of Radiotherapy in Acromegaly

Radiotherapy has, historically, played a central role in the management of acromegaly, and the last 30 years have seen substantial improvements in the technology used in the delivery of radiation therapy. More recently, the introduction of highly targeted radiotherapy, or 'radiosurgery', has further increased the therapeutic options available in the management of secretory pituitary tumors. Despite these developments, improvements in primary surgical outcomes, an increase in the range and effectiveness of medical therapy options, and long-term safety concerns have combined to dictate that, although still deployed in selected cases, the use of radiotherapy in the management of acromegaly has declined steadily over the past 2 decades. In this article, we review some of the main studies that have documented the efficacy of pituitary radiotherapy on growth hormone hypersecretion and summarize the data around its potential deleterious effects, including hypopituitarism, cranial nerve damage, and the development of radiation-related intracerebral tumors. We also give practical recommendations to guide its future use in patients with acromegaly, generally, as a third-line intervention after neurosurgical intervention in combination with various medical therapy options.

The History of Acromegaly

Pierre Marie coined the term 'acromegaly' in 1886 and linked it to a distinct clinical disease with a characteristic clinical picture. However, Pierre Marie was not the first physician to give a full record of the clinical picture of acromegaly; others had preceded him, like the Dutch physician Johannes Wier. After Marie, pituitary enlargement was noted in almost all patients with acromegaly. Subsequently it was discovered that pituitary hyperfunction caused by a pituitary tumour was indeed the cause of acromegaly. The cause of acromegaly could be further determined after the discovery of growth hormone (GH) and insulin-like growth factor I (IGF-I) and after demonstrating an association with GH hypersecretion and elevated circulating IGF-I. From the beginning of the 20th century, acromegaly could be treated by pituitary surgery and/or radiotherapy. After 1970, medical therapies were introduced that could control acromegaly. First, dopamine agonists were introduced, followed by somatostatin analogues and GH receptor blockers.

60 YEARS OF NEUROENDOCRINOLOGY: Acromegaly

Acromegaly (ACM) is a chronic, progressive disorder caused by the persistent hypersecretion of GH, in the vast majority of cases secreted by a pituitary adenoma. The consequent increase in IGF1 (a GH-induced liver protein) is responsible for most clinical features and for the systemic complications associated with increased mortality. The clinical diagnosis, based on symptoms related to GH excess or the presence of a pituitary mass, is often delayed many years because of the slow progression of the disease. Initial testing relies on measuring the serum IGF1 concentration. The oral glucose tolerance test with concomitant GH measurement is the gold-standard diagnostic test. The therapeutic options for ACM are surgery, medical treatment, and radiotherapy (RT). The outcome of surgery is very good for microadenomas (80-90% cure rate), but at least half of the macroadenomas (most frequently encountered in ACM patients) are not cured surgically. Somatostatin analogs are mainly indicated after surgical failure. Currently their routine use as primary therapy is not recommended. Dopamine agonists are useful in a minority of cases. Pegvisomant is indicated for patients refractory to surgery and other medical treatments. RT is employed sparingly, in cases of persistent disease activity despite other treatments, due to its long-term side effects. With complex, combined treatment, at least three-quarters of the cases are controlled according to current criteria. With proper control of the disease, the specific complications are partially improved and the mortality rate is close to that of the background population.

Percent reduction of growth hormone levels correlates closely with percent resected tumor volume in acromegaly

OBJECT

Correlation between tumor volume and hormone levels in individual patients would permit calculation of the fraction of tumor removed by surgery, by measuring postoperative hormone levels. The goals of this study were to examine the relationship between tumor volume, growth hormone (GH), and insulin-like growth factor–1 (IGF-1) levels, and to assess the correlation between percent tumor removal and the reduction in plasma GH and IGF-1 in patients with acromegaly.

METHODS

The 3D region of interest–based volumetric method was used to measure tumor volume via MRI before and after surgery in 11 patients with GH-secreting adenomas. The volume of residual tumor as a fraction of preoperative tumor volume was correlated with GH levels before and after surgery. Examination of this potential correlation required selection of patients with acromegaly who 1) had incomplete tumor removal, 2) had precise measurements of initial and residual tumor, and 3) were not on medical therapy.

RESULTS

Densely granulated tumors produced more peripheral GH per mass of tumor than sparsely granulated tumors (p = 0.04). There was a correlation between GH and IGF-1 levels (p = 0.001). Although there was no close correlation between tumor size and peripheral GH levels, after normalizing each tumor to its own plasma GH level and tumor volume, a comparison of percent tumor resection with percent drop in plasma GH yielded a high correlation coefficient (p = 0.006).

CONCLUSIONS

Densely granulated somatotropinomas produce more GH per mass of tumor than do sparsely granulated tumors. Each GH-secreting tumor has its own intrinsic level of GH production per mass of tumor, which is homogeneous over the tumor mass, and which varies greatly between tumors. In most patients the fraction of a GH-secreting tumor removed by surgery can be accurately estimated by simply comparing plasma GH levels after surgery to those before surgery.

Using growth hormone levels to detect macroadenoma in patients with acromegaly

BACKGROUND

The aim of this study was to assess the clinical differences between acromegalic patients with microadenoma and patients with macroadenoma, and to evaluate the predictive value of growth hormone (GH) levels for early detection of macroadenoma.

METHODS

We performed a retrospective analysis of 215 patients diagnosed with a GH-secreting pituitary adenoma. The patients were divided into two groups: the microadenoma group and the macroadenoma group, and the clinical parameters were compared between these two groups. The most sensitive and specific GH values for predicting macroadenoma were selected using receiver operating characteristic (ROC) curves.

RESULTS

Compared with the microadenoma group, the macroadenoma group had a significantly younger age, higher body mass index, higher prevalence of hyperprolactinemia and hypogonadism, and a lower proportion of positive suppression to octreotide. However, there were no significant differences in the gender or in the prevalence of diabetes between the two groups. The tumor diameter was positively correlated with all GH values during the oral glucose tolerance test (OGTT). All GH values were significantly higher in the macroadenoma group than the microadenoma group. Cut-off values for GH levels at 0, 30, 60, 90, and 120 minutes for optimal discrimination between macroadenoma and microadenoma were 5.6, 5.7, 6.3, 6.0, and 5.8 ng/mL, respectively. ROC curve analysis revealed that the GH value at 30 minutes had the highest area under the curve.

CONCLUSION

The GH level of 5.7 ng/mL or higher at 30 minutes during OGTT could provide sufficient information to detect macroadenoma at the time of diagnosis.

Prevalence of diabetes mellitus in patients with acromegaly

Early carbohydrate metabolism disorders (ECMDs) and diabetes mellitus (DM) are frequently associated with acromegaly. We aimed to assess the prevalence of ECMDs in patients with acromegaly and to compare the results with those in adults without acromegaly using two population-based epidemiologic surveys. We evaluated 97 patients with acromegaly in several phases of their disease (mean age, 56 years and estimated duration of acromegaly, 12.5 years). An oral glucose tolerance test was done in those not yet diagnosed with DM to reveal asymptomatic DM or ECMDs (impaired glucose tolerance+impaired fasting glucose). Comparisons were made between patients with acromegaly and participants from the general adult population (n=435) and an adult population with multiple type 2 diabetes risk factors (n=314), matched for gender, age and BMI. DM was diagnosed in 51 patients with acromegaly (52.5%) and 14.3% of the general population (P<0.001). The prevalence of ECMDs was also higher in patients with acromegaly than in the general population and in the high-risk group; only 22% of patients with acromegaly were normoglycaemic. The prevalence of newly diagnosed ECMDs or DM was 1.3-1.5 times higher in patients with acromegaly compared with the high-risk group. Patients with acromegaly having ECMDs or DM were older, more obese and had longer disease duration and higher IGF1 levels (Z-score). Logistic regression showed that the severity of glucose derangement was predicted by age, BMI and IGF1 levels. In patients with acromegaly, the prevalence of DM and ECMDs considerably exceeds that of the general population and of a high-risk group, and development of DM depends on age, BMI and IGF1 levels.

Serum IGF-1 in the diagnosis of acromegaly and the profile of patients with elevated IGF-1 but normal glucose-suppressed growth hormone

OBJECTIVE

To report the utility of insulin-like growth factor-1 (IGF-1) as a single biomarker for establishing the diagnosis of acromegaly and to examine the clinical and biochemical profile of patients with an elevated IGF-1 in whom a diagnosis of acromegaly could not be confirmed by means of the oral glucose tolerance test (OGTT).

METHODS

Between the years 1999 and 2010, we identified 101 patients who underwent pituitary surgery and had histologically proven somatotroph adenomas (Group 1, Gr 1). We selected 149 patients with non-growth hormone (GH) secreting pituitary macroadenomas (Gr 2, n = 97) and microadenomas (Gr 3, n = 52) to serve as control subjects. In addition, we identified 34 patients with elevated IGF-1values in whom acromegaly could not subsequently be proven by the OGTT (Gr 4).

RESULTS

IGF-1 was elevated in all patients with acromegaly prior to therapy with a median (range) standard deviation score (SDS) of +9.52 (+2.34 to +9.2), compared to SDS -1.46 (-2.91 to +2.17) and -1.22 (-2.8 to +1.58) in Gr 2 and 3, respectively (P<0.001). IGF-1 SDS values were +3.28 (+2.05 to +6.1), and IGF-1 was less than twice the upper limit of normal in all patients in Gr 4. OGTT was performed in 51 of the 101 acromegalic patients. The nadir GH in these patients was 4.01 (0.2 to 46.7) in comparison with 0.2 (<0.05 to 0.6) in Gr 4 (P<0.001).

CONCLUSION

Elevated IGF-1 levels, alone, are sufficient to establish a diagnosis of acromegaly in the majority of clinically suspected cases. The OGTT may be useful to obtain corroborative evidence when there is modest elevation of IGF-1 with absent or equivocal clinical features.

Nationwide survey of acromegaly in South Korea

CONTEXT

It was previously reported in Korea that there were 1.4 case per million per year of acromegaly. This was low in comparison with the extrapolated values of Western European countries. We expected that the incidence of acromegaly would be much higher now because of recently improved medical facilities, diagnostic tools and coverage of medical insurance to all the population of South Korea.

OBJECTIVE

The purpose of this nationwide survey was to examine the incidence and prevalence of patients with acromegaly, mode of treatment and outcome of surgical treatment of recent 5 years.

DESIGN AND PATIENTS

We requested and collected the medical records of all possible patients with acromegaly from 74 secondary or tertiary medical institutes in Korea from 2003 to 2007 retrospectively.

MEASUREMENTS

Date of diagnosis and treatment, tumour size, pre- and postoperative hormonal level, treatment modality and usage of medication were collected.

RESULTS

During 5 years, 1350 patients with acromegaly had been registered. The average annual incidence was 3.9 cases per million during this period, and prevalence had increased up to 27.9 cases per million in 2007. Male/female ratio was 1:1.2, and mean age at diagnosis was 44.1 years. Macroadenoma was dominant (82.9%). Transsphenoidal adenoidectomy was used the most as primary treatment (90.4%).

CONCLUSIONS

This Korean acromegaly survey offers a realistic overview of the predominant epidemiological characteristics of acromegaly in Korea. Annual incidence was at a similar level with western countries. Efforts to diagnose and control the disease earlier are recommended.

Acromegaly as a cause of 1,25-dihydroxyvitamin D-dependent hypercalcemia: case reports and review of the literature

Growth hormone excess has been associated with hypercalciuria and nephrolithiasis. Hypercalcemia in acromegaly is rare and usually due to coexistent primary hyperparathyroidism. To report two cases of 1,25-dihydroxyvitamin D (1,25 (OH)(2) D)-dependent hypercalcemia in cromegaly. A 50 year-old female with 2 years history of hypercalcemia presented with features of acromegaly. Serum calcium (Ca) was 10.9 mg/dl (8.6-10.2), parathyroid hormone (PTH) 20 pg/ml (10-65), PTH-related peptide undetectable, and 1,25 (OH)(2) D 119 pg/ml (15-75). Insulin-like growth factor 1 (IGF1) was 911 ng/ml (49-292) and growth hormone (GH) 14.5 ng/ml (0.03-10). MRI showed a 1.7 cm pituitary tumor. Transsphenoidal adenectomy (TSA) resulted in normalization of IGF1, GH, Ca, and 1,25 (OH)(2) D (50 pg/ml) and complete tumor resection. A 52-year-old female was diagnosed with visual field deficits on routine exam. MRI showed a 3 cm invasive pituitary macroadenoma. IGF1 was 416 ng/ml (87-238) and GH 75.8 (0-6.0) ng/ml. Incidentally, she was found with high Ca of 10.8 mg/dl (8.9-10.3) associated with PTH 19 pg/ml and 1,25 (OH)(2) D66 pg/ml. Postoperatively, IGF1 and GH remained abnormal (440 and 12.8 ng/ml, respectively), while MRI showed parasellar tumor residue. Ca remained high (10.1-11.1 mg/dl), along with elevated 1,25 (OH)(2) D level (81.3 pg/ml). In both cases, other causes of hypercalcemia were ruled out. We present 2 cases of 1,25 (OH)(2) D-dependent hypercalcemia associated with growth hormone excess. Complete resection of tumor produced biochemical remission of acromegaly and normalization of calcium and 1,25 (OH)(2) D levels, while incomplete resection was associated with persistent 1,25 (OH)(2) D-dependent hypercalcemia. Acromegaly should be considered a cause of 1,25 (OH)(2) D-dependent hypercalcemia.

The changing face of acromegaly--advances in diagnosis and treatment

Acromegaly is a chronic disease characterized by the presence of a pituitary growth hormone (GH)-producing tumour, excessive secretion of growth hormone, raised levels of insulin-like growth factor I (IGF-I) and characteristic clinical presentation of acral enlargement. Over the past two decades, major advances have occurred in the understanding of some aspects of acromegaly--such as the biology of pituitary tumours, the physiology, molecular mechanisms of GH secretion and IGF-I generation, and the pathogenesis of comorbidities. Moreover, new approaches to diagnosis and surveillance (both in terms of screening and follow-up) of acromegaly have led to increases in the number of patients diagnosed with active disease, many of whom would previously have been missed. The development of sensitive assays for detecting plasma GH and IGF-I levels, as well as the widespread use of MRI for visualization of small tumours, have been major contributing factors to these improvements. Treatment advances have resulted in improved cure rates and disease control through novel neurosurgical techniques and pharmacological approaches. This Review summarizes and discusses the changes in our understanding of the epidemiology, diagnosis, treatment, and follow-up of acromegaly and its comorbidities.

Glucose homeostasis in patients with acromegaly treated with surgery or somatostatin analogues

OBJECTIVE

Long-acting somatostatin analogues (SSA) are widely used for the treatment of acromegaly; however, they also alter β-cell function by inhibiting insulin secretion. In this study, we assess the effect of SSA on glucose homeostasis in patients with acromegaly treated with SSAs, compared to patients treated with surgery.

DESIGN

We studied four groups of patients with acromegaly: at the time of diagnosis (group I, n = 53), after successful transsphenoidal surgery (TSS, group II, n = 30) and under successful SSA treatment (group III, n = 20); 22 patients were studied only before treatment, 19 only post-treatment, while 31 patients (group IV) were studied before and after the treatment.

MEASUREMENTS

Patients underwent an oral glucose tolerance test. Insulin sensitivity and β-cell insulin secretion were estimated using appropriate mathematical models.

RESULTS

Control of acromegaly with either TSS or SSA improved insulin sensitivity as evident by significantly lower fasting and postglucose insulin levels and HOMA-IR. In addition, patients of group III compared to patients of group II demonstrated significantly lower HOMA-β% (52·5 ± 10·9 vs 189·6 ± 86·7, P < 0·05) and lower first and second phase insulin release (443 ± 83·5 vs 1077 ± 140·8, P < 0·05 and 150 ± 18·2 vs 285 ± 33·3, P < 0·05), respectively. Also, lower fasting glucose levels and a lower prevalence of diabetes were noted in group II compared to group III (5·1 ± 0·2 vs 6·2 ± 0·2 mm, P < 0·05, and 13·3%vs 40%, P < 0·0031, respectively). CONCLUSIONS; Control of acromegaly with SSA seems to exhibit a negative effect on pancreatic β-cell function. Whether this has long-term clinical implications remains to be established. Nevertheless, careful monitoring of glucose metabolism in patients under SSA is beneficial for their optimal management.

The insulin-like growth factor signaling pathway as a target for treatment of colorectal carcinoma

The insulin-like growth factors (IGFs), IGF1 and IGF2, are peptide hormones that bind to the insulin-like growth factor 1 receptor (IGF1R) and cause intracellular signaling that ultimately results in cellular growth and proliferation. Evidence from epidemiologic and preclinical studies suggests that IGF signaling may be of importance in the pathogenesis of colorectal cancer (CRC). In recent years, agents that target the IGF1R pathway have been developed. These agents are currently under evaluation for the treatment of CRC.

Endoscopic endonasal transsphenoidal surgery for growth hormone-secreting pituitary adenomas

OBJECT

The aim of this study was to determine the preoperative predictors of the extent of resection and endocrinological remission following endonasal endoscopic removal of growth hormone (GH)-secreting pituitary adenomas.

METHODS

The authors analyzed a prospectively collected database of 24 consecutive acromegalic patients who underwent endoscopic endonasal transsphenoidal surgery. The extent of resection was evaluated on postoperative contrast-enhanced MR imaging. Endocrinological remission was defined as normal insulin-like growth factor I (IGFI) serum levels and either a nadir GH level of < 0.4 ng/ml after an oral glucose load or a basal GH serum level < 1 ng/ml.

RESULTS

The majority of acromegalic patients (83%) had macroadenomas > 1 cm in maximum diameter. Gross-total resection was achieved in 17 (71%) of 24 patients. Notably, endoscopic transsphenoidal surgery allowed complete resection of all lesions without cavernous sinus invasion, regardless of the suprasellar extent. Biochemical remission was achieved in 11 (46%) of 24 patients. A smaller tumor volume and a postoperative reduction in GH serum levels were associated with a higher rate of biochemical cure (p < 0.05). During a 23-month follow-up period 5 patients (21%) underwent Gamma Knife treatment of any residual disease to further reduce excess GH production. Twenty patients (83%) reported significant relief of their symptoms, while 3 (13%) considered their symptoms stable. Two patients (8%) with large macroadenomas experienced postoperative panhypopituitarism, and 2 patients (8%) suffered from CSF leaks, which were treated with lumbar CSF diversion.

CONCLUSIONS

A purely endoscopic endonasal transsphenoidal adenoma resection leads to a high rate of gross-total tumor resection and endocrinological remission in acromegalic patients, even those harboring macroadenomas with wide suprasellar extension. Extended approaches and angled endoscopes are useful tools for increasing the extent of resection.

Clinical laboratory indices in the treatment of acromegaly

Measurement of serum growth hormone (GH) and insulin-like growth factor-I (IGF-) is used to monitor the degree of improvement that occurs following treatment of patients with acromegaly. Improvement in GH assay sensitivity has led to changes in the definition of normal GH however many studies that assess the predictive value of GH were conducted in an era where assays were less sensitive. Other problems that have occurred with GH measurements include utilization of different standards and failure to prove commutability of commonly accepted standard. GH reference ranges vary in their quality and are not stratified for age, sex or body mass index. IGF-I measurements are associated with similar problems. They do not use a common standard that has been proven to be commutable and results can vary widely when the same specimens are assayed in different laboratories. Although age and sex stratified reference ranges exist, these do not always have adequate numbers of subjects and BMI adjusted ranges are not available. These problems have led to significant discordance in a significant number of patients wherein the IGF-I and GH values may yield a discrepant prediction of disease stabilization. In these cases in general the IGF-I values correlate better with the presence of persistent symptoms. Patients who fail to suppress GH to normal but have a normal IGF-I have to be monitored carefully for recurrence but usually do not require further therapy if they are asymptomatic. For the long term assessment of outcome and clinical disease activity measurement of both hormones is recommended.

The endocrine tumor summit 2008: appraising therapeutic approaches for acromegaly and carcinoid syndrome

The Endocrine Tumor Summit convened in December 2008 to address 6 statements prepared by panel members that reflect important questions in the treatment of acromegaly and carcinoid syndrome. Data pertinent to each of the statements were identified through review of pertinent literature by one of the 9-member panel, enabling a critical evaluation of the statements and the evidence supporting or refuting them. Three statements addressed the validity of serum growth hormone (GH) and insulin-like growth factor-I (IGF-I) concentrations as indicators or predictors of disease in acromegaly. Statements regarding the effects of preoperative somatostatin analog use on pituitary surgical outcomes, their effects on hormone and symptom control in carcinoid syndrome, and the efficacy of extended dosing intervals were reviewed. Panel opinions, based on the level of available scientific evidence, were polled. Finally, their views were compared with those of surveyed community-based endocrinologists and neurosurgeons.

A case of fugitive acromegaly, initially presented as invasive prolactinoma

Fugitive acromegaly is most commonly caused by pituitary acidophil stem cell adenomas, and is characterized by a relatively short clinical history, a large and locally invasive tumor, and relatively low hormonal activity. Here, we report an unusual case of fugitive acromegaly that initially presented as invasive prolactinoma. A 48-year-old man with a huge pituitary mass extending to the suprasellar area was referred to our hospital in December 2007. He had undergone transsphenoidal surgery in November 1999 because of a large invasive prolactinoma. The tumor had grown progressively, despite therapy with dopamine agonists. Subtle features of acromegaly were noted and serum IGF-1 levels were high (733 ng/ml). An oral glucose tolerance test revealed that basal and nadir levels of growth hormone (GH) were 1.56 and 1 ng/ml, respectively. As a therapeutic trial, long-acting octreotide (20 mg IM, monthly) was added, and the tumor size markedly reduced within 6 months on magnetic resonance imaging examination. Immunohistochemical staining of the tumor tissue obtained at the surgery in 1999 showed positive staining for GH and prolactin (PRL). Double immunofluorescence staining showed a mixed positivity for GH and PRL in the majority of tumor cells; however, the two hormones colocalized in a minority of tumor cells, indicating that the tumor was composed of three different cell types (GH, PRL, and GH/PRL). The diagnosis of fugitive acromegaly was initially overlooked in this patient because of normal serum GH levels and a lack of acromegalic features, although histological evidence for GH production was present. IGF-1 determinations would be helpful for the diagnosis of fugitive acromegaly.

Gender differences in serum GH and IGF-I levels and the GH response to dynamic tests in patients with acromegaly

Gender affects the GH secretory pattern both in normal subjects and in patients with acromegaly by an uncertain mechanism. Here, we report the influence of gender on the relationship between serum GH and IGF-I levels and the GH response to dynamic tests in patients with acromegaly. Seventy-four patients with untreated acromegaly (M/F 27/47, age range 22-86 yr.) were studied. The serum GH levels did not differ between male and female (6.1 vs. 8.7 ng/ml; p=0.26), while serum IGF-I levels, IGF-I SDS and the IGF-I/GH ratio were lower in female than those in male (679 vs. 769 ng/ml; p<0.02, 7.3 vs. 9.2 SDS; p<0.02 and 79.6 vs. 141.5; p<0.05). When the subjects were divided into two groups: age <or=50 yr, and age >50 yr, serum IGF-I levels and IGF-I/GH ratios were lower in female than those in male in patients <or=50 yrs (650 vs. 1002 ng/ml; p<0.05 and 59.8 vs. 142.9; p<0.05), but not in patients >50 yrs (684 vs. 680 ng/ml; p=0.39 and 98.7 vs. 118.4; p=0.40). The GH responses to OGTT, TRH, octreotide, and bromocriptine tests were similar in male and female. In conclusion, IGF-I/GH ratio was significantly lower in female than that in male particularly in younger patients with acromegaly. These data suggest that gender, presumably sex steroids in female, may partially modulate the relationship between circulating IGF-I and GH levels in patients with acromegaly.

Spuriously Elevated Serum IGF-1 in Adult Individuals with Delayed Puberty: A Diagnostic Pitfall

Serum insulin-like growth factor-1 (IGF-1) is a sensitive marker of growth hormone (GH) activity. The levels of IGF-1 vary widely, peaking during puberty and declining with advancing age. During adolescence, serum IGF-1 levels tend to correlate better with pubertal stage rather than chronological age. Here we discuss two cases of delayed puberty, both in their 20s, who presented with high serum IGF-1 but no clinical or biochemical evidence of hypersomatotropism as confirmed by appropriate GH response to an oral glucose challenge. Both individuals achieved full pubertal status with testosterone replacement therapy and their serum IGF-1 levels settled into normal age-specific range. We suggest that in chronologically adult individuals with delayed puberty, serum IGF-1 should not be interpreted on the basis of age-specific normal values but rather on their pubertal status. Furthermore, in the absence of another cause of elevated IGF-1, the expectation is that IGF-1 levels will decline towards age-normative ranges following androgen replacement therapy.

Diagnostic challenges in acromegaly: a case-based review

Acromegaly is a rare, chronic condition caused by sustained and unregulated oversecretion of growth hormone (GH), usually attributed to a pituitary adenoma. Prolonged exposure to excessive amounts of GH and its target hormone, insulin-like growth factor-1 (IGF-1), results in pronounced metabolic changes and tissue enlargement that ultimately lead to increased morbidity and early mortality. As early diagnosis of acromegaly can have substantial beneficial effects on quality of life and overall survival for patients, it is important that the tests used to diagnose the condition are accurate, with highly reproducible results. The first kits used to measure GH and IGF-1 were radioimmunoassay, with many limitations that necessitated the development of more sensitive tools. Newer assays, although better than previous assays, are far from ideal. Simple changes that may improve the testing process include the adoption of mass units for GH interpretation and the use of a single recombinant calibrant. Furthermore, the conversion factors and reference ranges used to describe the normal limits for GH and IGF-1 levels require refinement. Physicians should be aware of the GH and IGF-1 assays used in their reference laboratories, and ensure that they know the appropriate assay cut-off values, to avoid misinterpreting results.

Acromegaly pathogenesis and treatment

Dysregulated growth hormone (GH) hypersecretion is usually caused by a GH-secreting pituitary adenoma and leads to acromegaly - a disorder of disproportionate skeletal, tissue, and organ growth. High GH and IGF1 levels lead to comorbidities including arthritis, facial changes, prognathism, and glucose intolerance. If the condition is untreated, enhanced mortality due to cardiovascular, cerebrovascular, and pulmonary dysfunction is associated with a 30% decrease in life span. This Review discusses acromegaly pathogenesis and management options. The latter include surgery, radiation, and use of novel medications. Somatostatin receptor (SSTR) ligands inhibit GH release, control tumor growth, and attenuate peripheral GH action, while GH receptor antagonists block GH action and effectively lower IGF1 levels. Novel peptides, including SSTR ligands, exhibiting polyreceptor subtype affinities and chimeric dopaminergic-somatostatinergic properties are currently in clinical trials. Effective control of GH and IGF1 hypersecretion and ablation or stabilization of the pituitary tumor mass lead to improved comorbidities and lowering of mortality rates for this hormonal disorder.

Acromegaly with normal IGF-1 levels probably due to poorly controlled diabetes mellitus

Acromegaly is characterized by the somatic disfigurement and excessive production of growth hormone (GH) and insulin-like growth factor-1 (IGF-1). Here we report a patient with aromegaly and diabetes mellitus, who showed normal IGF-1 levels in spite of elevated GH levels. The patient was a 52-year-old woman with acromegalic manifestations. Serum GH level was elevated (32.4 ng/mL) with hyperglycemia (fasting plasma glucose, 277 mg/dL) and an extremely high level of glycosylated hemoglobin (HbA1c 17.7%), whereas serum IGF-1 level was within normal range (110 ng/mL, normal range 37-266). Brain magnetic resonance imaging detected a pituitary tumor, with involvement of the right cavernous sinus. Oral glucose tolerance test (OGTT) showed no suppression of serum GH. Thyrotropin-releasing hormone test showed paradoxical increases in serum GH. We therefore diagnosed acromegaly accompanied with diabetes mellitus. A large amount of insulin (34 units/day) was required to control the blood glucose level. The patient was treated with octreotide, a somatostatin analogue, followed by transsphenoidal surgery. After the surgery, serum GH levels were suppressed by OGTT, although basal serum GH levels remained to be high. Basal serum GH levels, however, were normalized 5 months later. Blood glucose became well controlled by the diet alone. In contrast, serum IGF-1 increased to the range of 219-233 ng/mL. Pre-operative serum IGF-1 levels were low probably due to poorly controlled diabetes mellitus. In conclusion, the presence of normal serum IGF-1 levels cannot exclude the diagnosis of acromegaly especially when the patient is accompanied by diabetes mellitus.

Lower visceral and subcutaneous but higher intermuscular adipose tissue depots in patients with growth hormone and insulin-like growth factor I excess due to acromegaly

CONTEXT

GH and IGF-I are important regulators of metabolism and body composition. In acromegaly, a state of GH and IGF-I excess, the lipolytic and insulin antagonistic effects of GH may alter adipose tissue (AT) distribution.

OBJECTIVES

Our objective was to test the hypothesis that in acromegaly whole-body AT mass is less and to examine for the first time the relationship between GH/IGF-I excess and intermuscular AT (IMAT), an AT depot associated with insulin resistance in other populations.

DESIGN, SETTING, AND PATIENTS

We conducted a cross-sectional study in 24 adults with active acromegaly compared with predicted models developed in 315 healthy non-acromegaly subjects.

OUTCOME MEASURES

Mass of AT in the visceral AT (VAT), sc AT (SAT), and IMAT compartments from whole-body magnetic resonance imaging and serum levels of GH, IGF-I, insulin, and glucose were measured.

RESULTS

VAT and SAT were less in active acromegaly (P < 0.0001); these were 68.2 +/- 27% and 79.5 +/- 15% of predicted values, respectively. By contrast, IMAT was greater (P = 0.0052) by 185.6 +/- 84% of predicted. VAT/trunk AT ratios were inversely related to IGF-I levels (r = 0.544; P = 0.0054). Acromegaly subjects were insulin resistant.

CONCLUSIONS

VAT and SAT, most markedly VAT, are less in acromegaly. The proportion of trunk AT that is VAT is less with greater disease activity. IMAT is greater in acromegaly, a novel finding, which suggests that increased AT in muscle could be associated with GH-induced insulin resistance. These findings have implications for understanding the role of GH in body composition and metabolic risk in acromegaly and other clinical settings of GH use.

Rab18 is reduced in pituitary tumors causing acromegaly and its overexpression reverts growth hormone hypersecretion

CONTEXT

Rab proteins regulate the sequential steps of intracellular membrane transport. Alterations of these GTPases and their associated proteins are emerging as the underlying cause for several human diseases involving dysregulated secretory activities.

OBJECTIVE

Herein we investigated the role of Rab18, which negatively regulates hormone secretion by interacting with secretory granules, in relation to the altered functioning of tumoral pituitary somatotropes causing acromegaly.

PATIENTS

A total of 18 patients diagnosed with pituitary tumors causing acromegaly (nine patients) or nonfunctioning adenomas (nine patients) underwent endoscopic transsphenoidal surgery. Adenomas were subsequently processed to evaluate Rab18 production in relation to GH secretion.

RESULTS

We found that somatotropinoma cells are characterized by a high secretory activity concomitantly with a remarkably reduced Rab18 expression (15%) and protein content levels (30%), as compared with cells from nonfunctioning pituitary adenomas derived from patients with normal or reduced GH plasma levels (100%). Furthermore, immunoelectron microscopy revealed that Rab18 association with the surface of GH-containing secretory granules was significantly lower in somatotropes from acromegalies than nonfunctioning pituitary adenomas. Finally, we provide evidence that modulation of Rab18 gene expression can revert substantially the hypersecretory activity of cells because Rab18 overexpression reduced by 40% the capacity of cells from acromegalies to respond to GHRH stimulation.

CONCLUSION

These results suggest that molecular alterations affecting individual components of the secretory granule traffic machinery can contribute to maintain a high level of GH in plasma. Accordingly, Rab18 constitutes a valuable target as a diagnostic, prognostic, and/or therapeutic tool for human acromegaly.

Current diagnosis of acromegaly

Acromegaly is a rare and chronic condition that is characterized by sustained unregulated hypersecretion of growth hormone (GH). More than 99% of the cases of acromegaly are due to a pathologic proliferation of pituitary somatotrophs presenting in the form of a pituitary adenoma. The excessive amounts of GH and its target hormone, insulin like growth factor-1 (IGF-1) cause metabolic changes and tissue enlargement that, collectively, lead to significant morbidity and a two to threefold increase in mortality. Thus, early diagnosis has proved to be crucial to improve survival and quality of life in this condition. The development of radioimmunoassay (RIA) in the 1960s provided clinicians with a biochemical tool to diagnose acromegaly. Many limitations were inherent to this methodology which necessitated the development of more sensitive tools, such as immunoradiometric (IRMA) or immunoluminometric (ILMA) assays for GH and IGF-1 measurements. These newer assays have not come without imperfections. The reference ranges to describe normalcy of the somatotropic axis and the biochemical criteria of "cure" of acromegaly are areas of great debate. Nevertheless, the current international consensus agrees that the diagnosis of acromegaly should be based on both clinical presentation and biochemical data.

Management of growth hormone deficiency in adults

Growth hormone (GH) deficiency in adults is a recognised clinical entity. There is still, however, an ongoing debate of the clinical need and the importance of replacing GH in adults with severe GH deficiency. This review will focus on the overall management of adults with GH deficiency and highlight published data on dose management and treatment goals for various age groups. The efficacy data on quality of life and well-being is discussed and available and growing experience on long-term effects of GH replacement in adults and safety in terms of diabetes mellitus, pituitary tumour recurrence/regrowth and malignancy risk will be reviewed.

Acromegaly associated with type 2 diabetes showing normal IGF-1 levels under poorly controlled glycemia

Acromegaly is caused by excessive secretion of growth hormone (GH), and a resultant persistent elevation of insulin-like growth factor-1 (IGF-1) levels. Diabetes mellitus is accompanied in some acromegalic patients with insulin resistance. We encountered a type-2 diabetic patient who had a poorly controlled glycemic state and was diagnosed as acromegaly with normal IGF-1 levels. The patient showed definite acromegalic features. However, in the first screening test, GH levels were high and IGF-1 levels were inappropriately normal so the results were not close to the diagnosis of acromegaly. After moderate glycemic control, an oral glucose suppression test was performed, showing no suppressed GH response. TRH test revealed paradoxical increases in growth hormone levels and a brain MRI discovered a pituitary adenoma. After several-months insulin treatment, IGF-1 levels were increased to the abnormal state and GH levels were decreased without treatment for acromegaly. Here we report the rare case of acromegaly that presents inappropriately normal IGF-1 levels at the time of diagnosis in uncontrolled type 2 diabetic patient and shows increased IGF-1 levels after glycemic control with insulin therapy. When evaluating acromegaly in type 2 diabetes under poorly controlled glycemia, cautious IGF-1 analysis is needed after sufficient glycemic control.

Ensaios para a medida de hormônio do crescimento (GH) e IGF-I: aspectos metodológicos e suas implicações no diagnóstico e seguimento da acromegalia

A dosagem do GH no soro é essencial para confirmar ou excluir o seu excesso. Na acromegalia, a ausência de critérios clínicos suficientemente sensíveis para monitorizar o sucesso do tratamento faz com que o GH sérico seja o procedimento de escolha e, para isso, é essencial que a sua dosagem seja realizada de forma confiável, capaz de permitir interpretações uniformes. Vários critérios hormonais têm sido propostos para caracterizar remissão da acromegalia, incluindo níveis séricos de GH randômico inferior a 2,5 µg/l, nadir de GH durante o teste de tolerância oral a glicose inferior a 1,0 µg/l e IGF-I normal para sexo e idade. A importância do tratamento adequado consiste na possibilidade de reverter a mortalidade prematura da acromegalia através da diminuição dos níveis de GH para valores menores que 2,5 µg/l. Com o surgimento de ensaios ultra-sensíveis para medida do GH, tornaram-se necessários critérios mais estritos para determinar cura ou remissão da doença. Nesta revisão, descreveremos aqui as modificações decorrentes da evolução dos ensaios, as conseqüências nos resultados de GH e os pontos de corte propostos na literatura para caracterização da atividade e remissão da acromegalia.

Value of insulin-like growth factor system markers in the assessment of growth hormone status

Insulin-like growth factor-I (IGF-I) has been measured extensively in a variety of clinical settings. Total IGF-I frequently is used to assess the clinical impact of disorders of GH secretion and to monitor patients' response to therapy. It does not have sufficient precision to be used as a stand-alone test in the diagnosis of GH deficiency. Free IGF-I, IGF binding protein-3, or acid-labile subunit may provide useful information regarding GH secretion in specific conditions but are not superior to IGF-I for making the diagnosis of GH deficiency or acromegaly.

IGF-I assays: current assay methodologies and their limitations

The diagnosis of disorders of growth hormone (GH) is dependent upon accurate measurement of insulin-like growth factor-I (IGF-I) concentrations since serum IGF-I assays have been found to be useful as a screening tests for the presence of growth hormone deficiency (GHD) in children and in both children and adults they have been found very useful in establishing the diagnosis of acromegaly. IGF-I is also used extensively to monitor the response to GH treatment in children and adults and to monitor the response to treatment in acromegaly. Since IGF-I is influenced by several other hormones and physiologic factors as well as GH, a knowledge of its regulation is essential to understanding how to properly interpret the measurements. Several technical criteria are required for successful laboratory estimation of IGF-I values. These include elimination of interference of IGF-I-binding proteins (IGFBP), utilization of adequate numbers of normal subjects to define the normal ranges and importantly the use of high affinity, high specificity antisera that allow precise and reproducible measurements of the biologically active peptide. Cross comparisons of various commercial assays show that the results generally are similar when values are in the normal range. However, the assays have different performance characteristics when concentrations are either above or below the normal range. To obtain cross laboratory standardization for values outside the normal range requires utilization of similar, high-quality reagents and techniques that are reasonably comparable. Without this degree of standardization, cross comparisons among various reference laboratories are likely to continue to show wide divergence for values that are above or below the 95% confidence interval. A future goal should be the development of standard procedures and reagents that eliminate this degree of variability.

Gender, body weight, disease activity, and previous radiotherapy influence the response to pegvisomant

CONTEXT/OBJECTIVE

To effectively normalize IGF-I in patients with acromegaly, various covariates may affect dosing and plasma concentrations of pegvisomant. We assessed whether sex, age, weight, and previous radiotherapy influence dosing of pegvisomant in patients with active disease.

DESIGN

Data from 69 men and 49 women participating in multicenter, open-label trials of pegvisomant were retrospectively evaluated using multiple regression techniques. Sixty-nine subjects (39 men, 30 women) had undergone external beam pituitary radiotherapy. Serum IGF-I was at least 30% above age-related upper limit of normal in all patients at study entry. After a loading dose of pegvisomant (80 mg), patients were commenced on 10 mg/d. Pegvisomant dose was adjusted by 5 mg every eighth week until serum IGF-I was normalized.

RESULTS

At baseline, men had significantly higher mean serum IGF-I levels than women despite similar GH levels. After treatment with pegvisomant, IGF-I levels were similar in men and women. A significant correlation between baseline GH, IGF-I, body weight, and the dose of pegvisomant required to normalize serum IGF-I was observed (all P < 0.001). Women required an average of 0.04 mg/kg more pegvisomant than men and a mean weight-corrected dose of 19.2 mg/d to normalize serum IGF-I [14.5 mg/d (men); P < 0.001]. Patients treated with radiotherapy required less pegvisomant to normalize serum IGF-I despite similar baseline GH/IGF-I levels (15.2 vs. 18.5 mg/d for no previous radiotherapy; P = 0.002).

CONCLUSIONS

Sex, body weight, previous radiotherapy, and baseline GH/IGF-I influence the dose of pegvisomant required to normalize serum IGF-I in patients with active acromegaly.