Assessment of the magnitude of growth hormone hypersecretion in active acromegaly: reliability of different sampling models

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.

Mean GH profile is more accurate than single fasting GH in the evaluation of acromegaly disease control during somatostatin receptor ligands therapy

PURPOSE

This study aims to compare the accuracy of mean GH profile (GHP) < 2.5 ng/ml and single fasting GH (SGH) < 1 ng/ml in the evaluation of disease control in acromegaly patients during somatostatin receptor ligands (SRLs) therapy.

METHODS

We retrospectively enrolled 100 acromegaly patients, 68 responder, and 32 partial responder to SRLs. Controlled disease has been defined as IGF-I levels within age-related normal limits, while partial response as pathological IGF-I values despite a reduction ≥ 50%. In all patients, GHP, SGH, IGF-I, and IGFBP-3 were evaluated.

RESULTS

Median GHP levels (1.2 ng/ml, IQR 0.5-2.3 ng/ml) were lower (p = 0.001) than SGH (1.9 ng/ml, IQR 1.0-3.6 ng/ml). Accuracy of GHP was 81%, whereas that of SGH was 55%, with a Kappa index of 0.520 and 0.237, respectively. In multivariable analysis GHP (p = 0.002) and IGFBP-3 (p = 0.004), but not SGH, were independently associated with normal IGF-I levels. At receiver-operator characteristic curve (ROC) analysis GHP cut-off sensitivity and specificity were 94.1% and 50.0%, respectively, while SGH sensitivity and specificity were 35.3% and 93.7%, respectively. Finally, in obese patients the GH cut-off level (both as SGH and GHP) associated to good disease control was significantly different with respect to not obese ones.

CONCLUSIONS

GHP associates with IGF-I (and therefore with appropriate control of disease) with higher accuracy than SGH. When GH evaluation is needed, the measurement of mean GHP should be preferred and use of BMI-related cut-offs is suggested.

Growth hormone-Insulin-like growth factor 1 axis hyperactivity on bone fibrous dysplasia in McCune-Albright Syndrome

CONTEXT

In fibrous dysplasia (BFD), normal bone and bone marrow are replaced by fibro-osseous tissue, leading to fracture, deformity and pain. BFD may be isolated, or in association with cutaneous hyperpigmentation and/or hyperfunctioning endocrinopathies, termed McCune-Albright syndrome (MAS). GH hypersecretion has been described in 10%-20% of MAS-BFD patients. Aim of the study was to determine the impact of GH-insulin like growth factor 1 (IGF1) axis hyperactivity on MAS-BFD morbidities and the efficacy of GH excess therapy.

DESIGN AND PATIENTS

A multicentric cross-sectional analysis was conducted on three different MAS cohorts. From 195 MAS patients, 37 subjects (19%) with GH excess were identified and compared with 34 MAS controls without GH hypersecretion.

RESULTS

Mean head circumference SDS was significantly higher in GH excess: 4.025 SDS vs 0.683 SDS (P < .0001). The risk of optic neuropathy (Odds ratio 4.231; P = .039), hearing deficit (Odds ratio 2.961; P = .0481), facial asymmetry (Odds ratio 6.563; P = .0192), malignancies (Odds ratio 15.24; P = .0173) were higher in GH excess group. Overall, pharmacotherapy (octreotide alone 10-30 mg/mo or with pegvisomant 10-20 mg/d) was effective in IGF1 normalization (IGF1 Z-score between -2 and +2 SDS) in 21/29 patients (72.4%) with good compliance to the regimen. Late diagnosis and GH excess treatment after 16 years old of age was associated with an increased risk of optic neuropathy (Odds ratio 4.500; P = .0491) and growth of pituitary adenomas (Odds ratio 7.846; P = .050).

CONCLUSIONS

GH-IGF1 hyperactivity increases risk of morbidities in MAS. Medical therapy is effective in normalizing IGF1 in most patients, and early treatment during paediatric age is associated with a decreased risk of optic neuropathy and GH-secreting adenomas growth.

Acromegaly at diagnosis in 3173 patients from the Liège Acromegaly Survey (LAS) Database

Acromegaly is a rare disorder caused by chronic growth hormone (GH) hypersecretion. While diagnostic and therapeutic methods have advanced, little information exists on trends in acromegaly characteristics over time. The Liège Acromegaly Survey (LAS) Database, a relational database, is designed to assess the profile of acromegaly patients at diagnosis and during long-term follow-up at multiple treatment centers. The following results were obtained at diagnosis. The study population consisted of 3173 acromegaly patients from ten countries; 54.5% were female. Males were significantly younger at diagnosis than females (43.5 vs 46.4 years; P < 0.001). The median delay from first symptoms to diagnosis was 2 years longer in females (P = 0.015). Ages at diagnosis and first symptoms increased significantly over time (P < 0.001). Tumors were larger in males than females (P < 0.001); tumor size and invasion were inversely related to patient age (P < 0.001). Random GH at diagnosis correlated with nadir GH levels during OGTT (P < 0.001). GH was inversely related to age in both sexes (P < 0.001). Diabetes mellitus was present in 27.5%, hypertension in 28.8%, sleep apnea syndrome in 25.5% and cardiac hypertrophy in 15.5%. Serious cardiovascular outcomes like stroke, heart failure and myocardial infarction were present in <5% at diagnosis. Erythrocyte levels were increased and correlated with IGF-1 values. Thyroid nodules were frequent (34.0%); 820 patients had colonoscopy at diagnosis and 13% had polyps. Osteoporosis was present at diagnosis in 12.3% and 0.6-4.4% had experienced a fracture. In conclusion, this study of >3100 patients is the largest international acromegaly database and shows clinically relevant trends in the characteristics of acromegaly at diagnosis.

"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.

Tamoxifen as a therapeutic agent in acromegaly

OBJECTIVE

Administration of high doses of estrogens to patients with acromegaly has been shown to improve symptomatology of acromegaly and glucose tolerance more than 50 years ago. Selective estrogen receptor modulators (SERMs) mimic the effects of estrogen in bone, liver and the cardiovascular system, but function as an anti-estrogen in endometrial and breast tissue. In this study, we evaluated hormonal effects of a SERM, tamoxifen, in active acromegalic patients with particular emphasis on its use in males.

DESIGN

We studied 15 men and 2 post-menopausal women with biochemically-active acromegaly despite the fact that other modalities were ineffective in normalizing their insulin-like growth factor-1 (IGF-1) levels. All patients were treated with tamoxifen 20-40 mg daily for 2-11 months (median of 4 months).

METHODS

IGF-1 and growth hormone (GH) levels were assessed immediately before the beginning of treatment and at 2-4 monthly intervals thereafter. Baseline and treatment levels of total and bioavailable testosterone were measured in men.

RESULTS

Tamoxifen did not affect basal GH secretion, but it decreased circulating IGF-I in 14 patients (82%) by an average of 90 ± 4 mcg/L, (p = 0.005), and normalized plasma IGF-I in 8 patients (47%). Total and bioavailable testosterone levels increased in all evaluable men (n = 8). Tamoxifen was well tolerated.

CONCLUSION

Tamoxifen might be useful in the treatment of patients with biochemically-mild active acromegaly, but longer term studies are warranted.

Optic neuropathy in McCune-Albright syndrome: effects of early diagnosis and treatment of growth hormone excess

CONTEXT

GH excess is a serious complication of McCune-Albright syndrome (MAS) and has been associated with craniofacial morbidity.

OBJECTIVE

The aim of the study was to determine whether early diagnosis and treatment of MAS-associated GH excess prevents optic neuropathy and hearing impairment, the major morbidities associated with GH excess.

DESIGN AND SETTING

A retrospective cross-sectional analysis was conducted at a clinical research center.

PATIENTS

Twenty-two subjects with MAS-associated GH excess and 21 control MAS subjects without GH excess were included in the study.

INTERVENTION

Biochemical testing included random GH, nadir GH after glucose load, nadir GH on frequent sampling, and IGF-I Z-score. Subjects underwent imaging, ophthalmological, audiological, and otolaryngological assessment. Treatment included octreotide, pegvisomant, transphenoidal surgery, and/or radiotherapy as indicated.

MAIN OUTCOME MEASURE

Association of optic neuropathy and hearing impairment to age at GH excess diagnosis/treatment was measured.

RESULTS

Of 129 MAS subjects, 26 (20%) were diagnosed with GH excess based on elevation of two measures of GH function. Of these, 22 subjects were candidates for pharmacological intervention. Optic neuropathy was significantly correlated with intervention status, with no cases in the early intervention group (diagnosed/treated before age 18) or the control group, and four of seven (57%) in the late intervention group (diagnosed/treated after age 18) (Fisher's exact test; odds ratio, 0.027; P = 0.0058). Early diagnosis/intervention was not associated with reduction in hearing deficits (odds ratio, 1.25; P = 1.00). Mean head circumference SD score was significantly higher in the late (6.08; range, 2.70 to 22.56) than the early intervention (2.67; range, -0.65 to 6.72) or control groups (2.13; range, -2.06 to 7.79) (P = 0.003).

CONCLUSIONS

Early diagnosis/treatment of GH excess in MAS is important to prevent optic neuropathy and craniofacial expansion. The relationship between hearing deficits and GH excess remains less clear and requires further study.

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.

Quantification of day-to-day variability in growth hormone levels in acromegaly

Growth hormone (GH) measurements are routinely used for important treatment decisions in patients with acromegaly, yet their reliability is affected by numerous factors including assay precision and variability, sampling intensity, and hormone pulsatility. The day-to-day variation in GH in acromegaly has not been studied. This study quantified the magnitude of day-to-day GH variability in patients with acromegaly by performing an analysis of previously obtained plasma GH profiles. The analysis was performed at the Michigan Clinical Research Unit at the University of Michigan. A total of nine 48 h Q10 min GH profiles obtained in nine patients with active acromegaly were examined. The study was planned after data collection and analysis was conducted using Altman-Bland methods. Day 1 vs. Day 2 values were examined. 95% confidence intervals of the D2 vs. D1 ratios were calculated on all individual subject data as well as on a single 0800 h GH sample and composite mean data for 2-, 5-, 9-, and 24-h sampling protocols. Confidence interval range was 0.66-1.50 for the 0800 h sample and was similar for all sampling protocols except somewhat more narrow for the 24-h sampling (0.75-1.32). Daily variations in GH levels introduce an additional confounding element when using a single GH level or even daily GH curves to assess a patient's GH milieu. It may have an impact on result interpretation and subsequent treatment decisions especially when GH results are considered borderline.

The value of the oral glucose tolerance test, random serum growth hormone and mean growth hormone levels in assessing the postoperative outcome of patients with acromegaly

BACKGROUND

The nadir GH value following an oral glucose tolerance test (OGTT) and the mean GH levels obtained from a GH day curve (GHDC) are among the tools currently used for assessing therapeutic end-points in surgically treated acromegaly. The latter test, however, is cumbersome and costly.

OBJECTIVES

To evaluate, by using a modern, two-site chemiluminescent immunometric GH assay, the degree of discordance between the nadir GH following an OGTT and the mean GH obtained from a GHDC after surgical treatment of acromegaly and to check whether the OGTT can replace reliably the GHDC for the assessment of the disease status postoperatively.

PATIENTS AND METHODS

Forty-nine patients [25 males/24 females, median age 52 years (range 18-70)] with a GH-secreting pituitary adenoma who had been surgically treated previously underwent hormonal evaluation of their disease status. The GHDC comprised of 9 x 30-min samples for GH collected in the morning after an overnight fast and rest.

RESULTS

Seven per cent of patients with mean GH <1.7 mug/l (5 mU/l) in the GHDC had nadir GH >0.7 mug/l (2 mU/l) in the OGTT, and 10% of those with mean GH >1.7 mug/l had nadir GH <0.7 mug/l in the OGTT (all cases with discrepancies had normal IGF-I). GH value at time 0 min <0.6 mug/l in the OGTT had positive predictive value 100% and negative predictive value 75% in predicting nadir GH <0.3 mug/l (1 mU/l) in the OGTT. Nadir GH <0.8 mug/l in the OGTT had positive predictive value 97% and negative predictive value 95% in predicting mean GH <1.7 mug/l in the GHDC. Mean GH in the OGTT <1.4 mug/l had a positive predictive value 90% and negative predictive value 95% in predicting mean GH <1.7 mug/l in the GHDC. Mean GH in the OGTT <2.5 mug/l had positive predictive value 100% and negative predictive value 81% in predicting normal IGF-I. GH at time 0 min in the GHDC <2.1 mug/l had positive predictive value 90% and negative predictive value 90% in predicting mean GH <1.7 mug/l in the GHDC.

CONCLUSIONS

The hormonal data obtained from an OGTT (mean and nadir GH) can provide comprehensive information on the status of acromegaly following surgery and can replace the GHDC cost-effectively. Furthermore, a morning fasting GH sample has an excellent positive predictive value in predicting biochemical cure and an optimal prognostic profile in predicting "safe" mean GH levels.

Monitoring of acromegaly: what should be performed when GH and IGF-1 levels are discrepant?

Monitoring of a patient with acromegaly requires periodic evaluation of levels of GH and IGF-1, the biochemical markers of this disease. Although the results of these two tests are usually concordant, they can be discrepant and how to proceed when they are can be a challenging clinical problem. In some cases, IGF-1 levels are normal yet GH suppression after oral glucose is abnormal; this pattern may be due to persistent GH dysregulation despite remission. In other cases, IGF-1 levels are elevated yet GH suppression appears to be normal; this pattern may be observed if the cutoff for GH suppression is inappropriately high for the GH assay being used. Various conditions known to alter GH and IGF-1 including malnutrition, thyroid disease and oestrogen use as well as the potential for methodological or normative data issues with the GH and IGF-1 assays should be considered in the interpretation of discrepant results. When a known cause of the discrepancy other than acromegaly is not identified, a clinical decision about the patient's therapy needs to be made. We adjust treatment in most patients whose results are discrepant based on the IGF-1 level, continuing current treatment if it is persistently normal or modifying this if it is elevated. The clinical picture of the patient, however, also needs to be incorporated into this decision. All patients should have continued periodic surveillance of both GH and IGF-1 levels.

Monitoring disease activity using GH and IGF-I in the follow-up of 501 patients with acromegaly

CONTEXT

The aims of treatment in patients with acromegaly are to achieve serum GH/IGF-I concentrations associated with cure or normalization of mortality and alleviation of symptoms.

OBJECTIVE AND METHODS

Using the West Midlands Acromegaly database (n = 501) we investigated the reliability of basal fasting GH in predicting nadir or mean GH during oral glucose tolerance test (OGTT) or GH day curve (GHDC), respectively, the degree of discordance between disease activity measured by GH and IGF-I values and the effect of radiotherapy on the above relationships. In total 773 OGTT and 507 GHDC were performed.

RESULTS

Basal fasting GH was strongly correlated with nadir/mean GH on OGTT/GHDC (r = +0.87, P < 0.0001, r = +0.93, P < 0.0001, respectively). A basal GH < 2.5 microg/l was associated with a nadir/mean GH during OGTT/GHDC < 2.5 microg/l in 98.6% and 88.2% of cases, respectively. Elevated IGF-I was seen in 32.4% and 46.4% of patients with GH nadir values during OGTT < 1 and < 2.5 microg/l, respectively, and in 21.2% and 45.9% of GHDC with mean GH < 1 and < 2.5 microg/l, respectively. Radiotherapy increased the discordance in GH and IGF-I as markers of disease activity at GH < 2.5 microg/l (elevated IGF-I-values when OGTT nadir GH < 2.5 microg/l: radiotherapy 55.5%vs. no radiotherapy 36.9%, P = 0.002).

CONCLUSIONS

There is a close relationship between a basal fasting GH < 2.5 microg/l and nadir/mean GH < 2.5 microg/l during OGTT/GHDC. There is a large discordance between disease activity when assessed by GH and IGF-I which is further increased by radiotherapy. These observations illustrate the challenge of defining appropriate biochemical end-points to achieve control of disease and normalization of mortality in acromegaly.