Pitfalls in the biochemical assessment of acromegaly

Impact of Variation between Assays and Reference Intervals in the Diagnosis of Endocrine Disorders

Method-related variations in the measurement of hormones and the reference intervals used in the clinical laboratory can have a significant, but often under-appreciated, impact on the diagnosis and management of endocrine disorders. This variation in laboratory practice has the potential to lead to an errant approach to patient care and thus could cause harm. It may also be the source of confusion or result in excessive or inadequate investigation. It is important that laboratory professionals and clinicians know about these impacts, their sources, and how to detect and mitigate them when they do arise. In this review article, we describe the historical and scientific context from which inconsistency in the clinical laboratory arises. Examples from the published literature of the impact of the method, reference interval, and clinical decision threshold-related discordances on the assessment and monitoring of various endocrine disorders are discussed to illustrate the sources, causes, and effects of this variability. Its potential impact on the evaluation of growth hormone deficiency and excess, thyroid and parathyroid disorders, hyperandrogenism, hypogonadism, glucocorticoid excess and deficiency, and diabetes mellitus is elaborated. Strategies for assessment and mitigation of the discordance are discussed. The clinical laboratory has a responsibility to recognise and address these issues, and although a lot has been accomplished in this area already, there remains more to be done.

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.

Acromegaly-related cutis verticis gyrata

OBJECTIVE

Acromegaly is a disorder caused by hypersecretion of growth hormone (GH), resulting in excessive levels of insulin-like growth factor 1 (IGF-1), and almost always due to a pituitary tumor. It is classically associated with acral enlargement, prominent facial features and soft tissue overgrowth. Skin manifestations include hirsutism, acne, skin tags, oily skin and acanthosis nigricans. However, other uncommon dermatological features, such as cutis verticis gyrata (CVG), may also occur. Here, we review acromegaly-related CVG aiming to raise awareness for its possible occurrence in this setting, and we discuss its pathophysiology, presentation, management and differential diagnosis.

DESIGN

A comprehensive literature search regarding CVG, particularly CVG related to acromegaly, has been carried out. Case reports, original studies and review papers, were considered.

RESULTS

CVG is a rare benign skin lesion characterized by thickened and folded scalp, resembling the brain gyri and sulci. The diagnosis of CVG mainly relies on clinical examination, although tissue biopsy may be necessary in case of uncertain etiology. In acromegaly, CVG appears to be driven by the trophic effects of GH and IGF-1 on skin and soft tissues. While CVG is uncommon in acromegaly, it seems to occur more frequently in male patients. The management of acromegaly-related CVG essentially relies on controlling the serum levels of GH and IGF-1. Surgical skin procedures should be reserved for patients with severe aesthetic distress, after achieving the best possible control of acromegaly.

CONCLUSIONS

CVG is a rare manifestation of acromegaly that may allow an earlier diagnosis and a swifter treatment of these patients, which in turn may improve or entirely reverse such remarkable skin lesions.

The biochemical diagnosis of acromegaly: revising the role of measurement of IGF-I and GH after glucose load in 5 questions

INTRODUCTION

Acromegaly is a rare disorder characterized by the excessive secretion of growth hormone (GH), mostly caused by pituitary adenomas. While in full-blown cases the diagnosis is easy to establish, milder cases are more challenging. Additionally, establishing whether full cure after surgery is reached may be difficult.

AREAS COVERED

In this article, we will review the challenges posed by the variability in measurements of GH and its main effector insulin-like growth factor I (IGF-I) due to both biological changes, co-morbidities, and assays variability.

EXPERT OPINION

Interpretation of GH and IGF-I assays is important in establishing an early diagnosis of acromegaly, in avoiding misdiagnosis, and in establishing if cure is achieved by surgery. Physicians should be familiar with the variables that affect measurements of these 2 hormones, and with the performance of the assays available in their practice.

The Biochemical Diagnosis of Acromegaly

Background: The diagnosis of acromegaly still poses a clinical challenge, and prolonged diagnostic delay is common. The most important assays for the biochemical diagnosis and management of acromegaly are growth hormone (GH) and insulin-like growth factor-1 (IGF-1). Objective: Discuss the role of IGF-1, basal serum GH, and nadir GH after oral glucose tolerance test (OGTT) for the diagnosis, management, and treatment of patients with acromegaly. Methods: We performed a narrative review of the published data on the biochemical diagnosis and monitoring of acromegaly. An English-language search for relevant studies was conducted on PubMed from inception to 1 January 2021. The reference lists of relevant studies were also reviewed. Results: Serum IGF-1 levels, basal GH values, and nadir GH after OGTT play a major role in the diagnosis, management, and treatment of patients with acromegaly. Measurement of IGF-1 levels is the key factor in the diagnosis and monitoring of acromegaly, but basal and nadir GH following OGTT are also important. However, several factors may significantly influence the concentrations of these hormones, including assay methods, physiologic and pathologic factors. In some cases, discordant GH and IGF-1 levels may be challenging and usually requires additional data and monitoring. Conclusion: New GH and IGF-1 standards are much more precise and provide more accurate tools to diagnose and monitor patients with acromegaly. However, all these biochemical tools have their limitations, and these should be taken under consideration, along with the history, clinical features and imaging studies, when assessing patients for acromegaly.

Is GH nadir during OGTT a reliable test for diagnosis of acromegaly in patients with abnormal glucose metabolism?

PURPOSE

The growth hormone (GH) nadir during oral glucose tolerance test (OGTT) is the gold standard diagnostic test for acromegaly. The utility of OGTT-GH suppression test in patients with abnormal glucose metabolism (AGM) has not been well established. In this study, we compared the GH nadir during OGTT in patients evaluated for acromegaly in the presence and absence of AGM.

METHODS

This is a retrospective cohort study of patients with acromegaly (G1, n = 40) and a group in whom acromegaly was not confirmed (G2, n = 53) who had OGTT-GH suppression test during 2000-2012, using a monoclonal GH immunoenzymatic assay. The patients were categorized as having normal glucose metabolism (NGM) or AGM. GH nadir during OGTT in each group were compared.

RESULTS

In G1 and G2, 17 and 19 patients had AGM, respectively. Among 17 patients with diabetes, median HbA1C was 7% (range 5.7-9.6%). All except one patient had HbA1C< 8%. There was no difference in the GH nadir in patients with or without AGM within G1 (p = 0.15) and G2 (p = 0.43). All G1 patients with AGM had GH nadir > 0.4 µg/L. Four G1 patients with NGM had GH nadir<0.4 µg/L. All G2 patients had GH nadir < 0.4 µg/L, except one with NGM and GH nadir of 0.4 µg/L.

CONCLUSION

Using highly sensitive GH assay, a GH nadir ≥ 0.4 µg/L during the OGTT-GH suppression test may be used for diagnosis of acromegaly in patients with AGM in the absence of poorly controlled diabetes.

Value of early postoperative random growth hormone levels and nadir growth hormone levels after oral glucose tolerance testing in acromegaly

OBJECTIVE

There is no ideal marker to identify residual tumor tissue after surgery in patients with acromegaly. The purpose was to elucidate if early postoperative hormone testing gives reliable information regarding complete resection of a GH-producing pituitary adenoma.

DESIGN

Fourty-eight patients undergoing surgery for acromegaly from 04/2013-05/2014 were prospectively examined for random GH, IGF1, and GH levels after oral glucose tolerance testing (OGTT) in the early postoperative phase and on follow-up. Criterion for inclusion was a minimum follow-up of one year for each patient with respect to remission.

RESULTS

Thirty-three patients showed GH suppression below 1 μg/l after OGTT in the early postoperative phase. Follow-up GH, IGF1 and OGTT tests confirmed the initial findings in 30 patients. The three remaining patients showed biochemical signs of persisting acromegaly. In the remaining 15 patients early postoperative GH suppression was above 1 μg/l. Of those, six patients went into remission during follow-up, nine patients without postoperative GH suppression <1 μg/l remained acromegalic.

CONCLUSIONS

GH suppression to <1 μg/l as well as random GH levels below 1 μg/l in the early postoperative phase seem to be of good positive predictive value for long-term remission. However, several patients without suppression of GH to <1 μg/l in the early postoperative OGTT went into delayed remission. These results have to be taken into account prior to initiation of further therapy.

Biochemical investigations in diagnosis and follow up of acromegaly

Measurements of human growth hormone (GH) and insulin-like growth-factor I (IGF-I) are cornerstones in the diagnosis of acromegaly. Both hormones are also used as biochemical markers in the evaluation of disease activity during treatment. Management of acromegaly is particularly challenging in cases where discordant information is obtained from measurement of GH concentrations following oral glucose load and from measurement of IGF-I. While in some patients biological factors can explain the discrepancy, in many cases issues with the analytical methods seem to be responsible. Assays used by endocrine laboratories to determine concentrations of GH and IGF-I underwent significant changes during the last decades. While generally leading to more sensitive and reproducible methods, these changes also had considerable impact on absolute concentrations measured. This must be reflected by updated decision limits, cut-offs and reference intervals. Since different commercially available assays do not agree very well, method specific interpretation of GH and IGF-I concentrations is required. This complexity in the interpretation of hormone concentrations is not always appropriately reflected in laboratory reports, but also not in clinical guidelines reporting decision limits not related to a specific analytical method. The present review provides an overview about methodological and biological variables affecting the biochemical assessment of acromegaly in diagnosis and follow up.

Detection of Growth Hormone Deficiency in Adults with Chronic Traumatic Brain Injury

This study examined the prevalence of growth hormone deficiency (GHD) in patients with traumatic brain injury (TBI) during the post-acute phase of recovery and whether GHD was associated with increased disability, decreased independence, and depression. A secondary objective was to determine the accuracy of insulin-like growth factor-1 (IGF-1) levels in predicting GHD in patients with TBI. Anterior pituitary function was assessed in 235 adult patients with TBI through evaluation of fasting morning hormone levels. GH levels were assessed through provocative testing, specifically the glucagon stimulation test. GHD was diagnosed in a significant number of patients, with 45% falling into the severe GHD (≤3 μg/L) category. IGF-1 levels were not predictive of GHD. Patients with GHD were more disabled and less independent compared with those patients who were not GHD. Those patients with more severe GHD also showed decreased levels of cortisol and testosterone. Symptoms of depression were also more prevalent in this group. In addition, patients with severe GHD had delayed admission to post-acute rehabilitation. This study confirms the high prevalence of GHD in patients with TBI and the necessity to monitor clinical symptoms and perform provocative testing to definitively diagnose GHD.

Discordance between growth hormone and insulin-like growth factor-1 after pituitary surgery for acromegaly: a stepwise approach and management

INTRODUCTION

Follow-up management of patients with acromegaly after pituitary surgery is performed by conducting biochemical assays of growth hormone (GH) and insulin-like growth factor-1 (IGF1). Despite concordant results of these two tests in the majority of cases, there is increasing recognition of patients who show persistent or intermittent discordance between GH and IGF1 (normal GH and elevated IGF1 or vice versa).

METHOD

In this narrative review, the last three decades materials on the issue of discrepancy between GH and IGF1 were thoroughly assessed.

RESULTS

Various studies have obtained different discordance rates, ranging from 5.4 to 39.5%. At present, despite the use of current sensitive assays and more stringent criteria to define remission, the rate of discordance still remains high. A number of mechanisms have been proposed to explain the postoperative discordance of GH and IGF1 including; altered dynamics of the GH secretion after surgery, early postoperative hormone assay, inaccurate or less sensitive tests and laboratory errors, too high cut-off point for GH suppression in the GH assays, GH nadir values not adjusted to age, sex, and body mass index, the influence of concomitant medication, co-existing physiologic and pathologic conditions, and many other proposed reasons. Nevertheless, the underlying mechanisms are still far from clear, and the solution continues to evade complete elucidation. Similarly, the impacts of such a discrepancy over mortality and morbidity and the risk of biochemical and/or clinical recurrence are unclear.

CONCLUSION

As a challenging clinical problem, a stepwise evaluation and management of these patients appears to be more rational.

Janus kinase (JAK) 2 V617F mutation as the cause of primary thrombocythemia in acromegaly with severe visceromegaly and divergence between growth hormone and insulin-like growth factor-1 concentrations during the follow-up: causal or casual association?

OBJECTIVE

An increased prevalence of hematological abnormalities is reported in acromegaly, but to date no reports about the presence of the Janus Kinase (JAK) 2 mutation in acromegalic patients have been described.

DESIGN

We report the complex clinical presentation of the unique case, never described, of acromegaly due to GH-secreting pituitary adenoma associated with JAK2 V617F mutation.

RESULTS

The patient shows primary thrombocythemia and myelofibrosis, due to JAK2 V617F mutation, severe visceromegaly and a peculiar clinical course of the disease characterized by discrepant values of GH and IGF-1 during somatostatin analog (SA) treatment despite a significant reduction in pituitary adenoma size and therapeutic resistance both to SA and pegvisomant.

CONCLUSIONS

The presence of JAK2 V617F mutation is a cause of primary thrombocythemia and myelofibrosis in acromegaly. In this patient, a peculiar clinical course of acromegaly was observed, with the difficulty in controlling the disease. More data, on a larger cohort of patients, could clarify whether JAK2 V617F mutation has a serious impact on the clinical features and course of acromegaly.

Pituitary incidentaloma

Pituitary incidentalomas (PIs) are commonly encountered in clinical practice. While most are microincidentalomas (<1 cm) and not functional, in some cases their identification may lead to discovery of unrecognized abnormalities such as pituitary hormonal deficiencies, excess hormone secretion or visual field defects. Although the majority are pituitary adenomas, the potential list of differential diagnosis is extensive. A limited biochemical work up for asymptomatic patients with microincidentalomas, to include measurement of prolactin and IGF-1, is reasonable, with further studies to be tailored based on the clinical picture. All patients with macroincidentalomas (≥1 cm) should be evaluated for hypopituitarism and undergo visual field testing if the sellar mass abuts or compresses the optic chiasm. Most PIs can be followed, closely without surgery over time, but some may require surgical removal, especially if they are found to be macroincidentalomas at presentation, encroaching on or abutting the optic chiasm, or are found to be functional, excluding prolactinomas. Recovery of pituitary function may be seen in some patients with mass effect following resection of a sellar mass. The association of headache and pituitary incidentalomas remains a diagnostic challenge. There are no randomized controlled studies to guide the follow up approach when surgery is not indicated; most of the follow up algorithms in the literature are based on personal experience. Most retrospective series on natural history indicate that microincidentalomas tend not to grow; without a need for long-term follow up unless the patient becomes symptomatic. Macroincidentalomas, on the other hand, have a propensity to grow and need a more aggressive follow up approach to minimize morbidity.

Medical therapy of acromegaly

This paper outlines the present status of medical therapy of acromegaly. Indications for permanent postoperative treatment, postirradiation treamtent to bridge the interval until remission as well as primary medical therapy are elaborated. Therapeutic efficacy of the different available drugs-somatostatin receptor ligands (SRLs), dopamine agonists, and the GH antagonist Pegvisomant-is discussed, as are the indications for and efficacy of their respective combinations. Information on their mechanism of action, and some pharmakokinetic data are included. Special emphasis is given to the difficulties to define remission criteria of acromegaly due to technical assay problems. An algorithm for medical therapy in acromegaly is provided.

Management of acromegaly in Latin America: expert panel recommendations

Although there are international guidelines orienting physicians on how to manage patients with acromegaly, such guidelines should be adapted for use in distinct regions of the world. A panel of neuroendocrinologists convened in Mexico City in August of 2007 to discuss specific considerations in Latin America. Of major discussion was the laboratory evaluation of acromegaly, which requires the use of appropriate tests and the adoption of local institutional standards. As a general rule to ensure diagnosis, the patient's GH level during an oral glucose tolerance test and IGF-1 level should be evaluated. Furthermore, to guide treatment decisions, both GH and IGF-1 assessments are required. The treatment of patients with acromegaly in Latin America is influenced by local issues of cost, availability and expertise of pituitary neurosurgeons, which should dictate therapeutic choices. Such treatment has undergone profound changes because of the introduction of effective medical interventions that may be used after surgical debulking or as first-line medical therapy in selected cases. Surgical resection remains the mainstay of therapy for small pituitary adenomas (microadenomas), potentially resectable macroadenomas and invasive adenomas causing visual defects. Radiotherapy may be indicated in selected cases when no disease control is achieved despite optimal surgical debulking and medical therapy, when there is no access to somatostatin analogues, or when local issues of cost preclude other therapies. Since not all the diagnostic tools and treatment options are available in all Latin American countries, physicians need to adapt their clinical management decisions to the available local resources and therapeutic options.

Measurement of human growth hormone by immunoassays: current status, unsolved problems and clinical consequences

Measuring the concentration of growth hormone (GH) in blood samples taken during dynamic tests represents the basis for diagnosis of growth hormone related disorders, namely growth hormone deficiency and growth hormone excess. Today, a wide spectrum of immunoassays are in use, enabling rapid and sensitive determination of growth hormone concentrations in routine diagnostics. From a clinical point of view several difficulties exist with the use and interpretation of GH assay results in the assessment of GH related disorders: Many physiological factors such as fat mass, age and gender influence the outcome of dynamic tests, overall leading to significant inter-individual differences in GH responses. However, in addition to the physiological variability, considerable variability exists in GH assay results obtained by different immunoassays. Unfortunately, all the new technical advances in the field of GH measurement techniques have not reduced this methodological variability. To a large extent, the actual values reported for the GH concentration in a sample depend on the method used by the respective laboratory. Obviously, such discrepancies limit the applicability of consensus guidelines on diagnosis and treatment in clinical practice. This review summarizes current practices for GH measurement with respect to the methods used, their limitations and the clinical consequences of the existing heterogeneity in GH immunoassay results.

High prevalence of biochemical acromegaly in primary care patients with elevated IGF-1 levels

OBJECTIVE

The estimated prevalence of acromegaly is 40-125 per million. The diagnosis of acromegaly is often delayed due to deficits in recognizing the signs of the disease. It is not known how many subjects with increased IGF-1 levels have acromegaly. We aimed to assess the prevalence of acromegaly in primary care by screening for elevated IGF-1 levels.

DESIGN

A cross-sectional, epidemiological study (the DETECT study). Patients A total of 6773 unselected adult primary care patients were included.

MEASUREMENTS

We measured IGF-1 in all patients and recommended further endocrine evaluation in all patients with elevated IGF-1 levels (> 2 age-dependent SDS).

RESULTS

Of 125 patients with elevated IGF-1 levels, 76 patients had indeterminate results and acromegaly could be excluded in 42 patients. One patient had known florid acromegaly. Two patients had newly diagnosed acromegaly and pituitary adenomas. Four patients had biochemical acromegaly but refused further diagnostics. This corresponds to a prevalence of 1034 per million patients.

CONCLUSIONS

Our study shows a high prevalence of undiagnosed acromegaly in primary care. These results imply that acromegaly is underdiagnosed and stress the importance of detecting acromegaly.

Guidelines for the treatment of growth hormone excess and growth hormone deficiency in adults

The V Consensus Group Meeting on 'Guidelines for Treatment of GH Excess and GH Deficiency in the Adult' was an international workshop held on February 20-22, 2006 in Santa Monica, California, USA. The principal aim of this meeting was to provide guidelines for the evaluation and treatment of adults with either form of abnormal GH secretion: GH excess or GH deficiency. The workshop included debates as to the choice of primary treatment, discussions of the targets for adequate treatment, and concluded with presentations on open issues germane to adult GH treatment including the role of GH in malignancies, the impact of longterm treatment on bone, and a cost-benefit analysis. The meeting was comprised of 66 delegates representing 13 different countries.

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.

Dynamic tests for the diagnosis and assessment of treatment efficacy in acromegaly

In the vast majority of cases, basal serum GH and IGF-1 levels are markedly increased in patients with obvious clinical signs and symptoms of acromegaly. The oral glucose tolerance test (OGTT) is useful for diagnosis in the minority of patients who have weak GH hypersecretion. The cutoff for a "normal" GH nadir in the OGTT remains to be agreed. The type of GH assay, its sensitivity, the type of standard used by the manufacturer, the patient's age and especially gender, must all be taken into account. Recent studies using new highly sensitive assays suggest an upper normal GH nadir of 0.71 microg/l for female healthy patients, but no "universal" cut-off has yet been defined for healthy males (from 0.057 to 0.25 microg/l). The 1 microg/l cutoff proposed for the diagnosis of acromegaly in a 2000 consensus should be abandoned in favor of a 0.30 microg/l cutoff. Clinicians should know which assay is used, together with its sensitivity and the standard, before making therapeutic decisions. A more pragmatic view should probably be adopted when assessing the treatment response. Indeed, if "cure" is defined not with the <1 microg/l GH nadir but on the basis of healthy control values, many patients will not be considered controlled. However, the clinical relevance of such goal (e.g. achieving GH nadir <0.4 microg/l rather than <1 microg/l) in terms of prognosis and prediction of outcome on long term is not firmly established. Thus, from a pragmatic point of view, achieving a normal age-adjusted IGF-1 level and a GH nadir below 1 microg/l during OGTT will probably remain relevant for defining remission and good disease control in terms of morbidity and mortality in acromegaly.

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.

Defining normalcy of the somatotropic axis: an attainable goal?

The diagnoses of acromegaly and dwarfism require biochemical confirmation of abnormal GH and IGF-1 concentrations. The same parameters are used for therapeutic decisions, i.e. initiation or termination of particular treatments. Therefore, reliable and epidemiologically and statistically proven criteria of normalcy for GH and IGF-1 are required for these tasks to be accomplished. Despite major progress in all these areas, the definition of what constitutes "normalcy" of the somatotropic axis is still lacking. Using an example of acromegaly, we discuss the contradictions and the uncertainties of the biochemical diagnosis of this disease.

Transsphenoidal microsurgery for newly diagnosed acromegaly: a personal view after more than 1,000 operations

The aim of this short review is to inform about the possibilities and limits of transnasal microsurgery in acromegaly. The current reports on surgical remissions, according to the strict criteria with international consensus using age- and sex-related normal levels for insulin-like growth factor-I and suppression of growth hormone (GH) with oral glucose tolerance below 1 mug/l, are more or less agreeable with values between 34 and 74%. In microadenomas (<10 mm in diameter), 59-95% remissions are published. Some improvement might be achieved in macroadenomas which presently have a chance of 26-68% to be satisfactorily operated on. Special instruments introduced by us to visualize and remove partially invasive adenoma parts are described. Intraoperative magnetic resonance imaging is discussed. With intraoperative measurement of GH, small adenoma rests <3 mm can be diagnosed. When GH did not sufficiently decline, an additional tumor search resulted in a significant improvement in results in resectable macroadenomas. With these techniques, we achieved remission rates which can hardly be further increased (micros 95%, macros 68%). In grossly invasive grade 4 adenomas, which are frequent in our unit, only an 80-95% reduction in tumor mass is feasible. Preoperative treatment with somatostatin analogues as used in most of our patients reduces the comorbidity and facilitates adenoma removal which is still controversially discussed in the literature. The complication rate of microsurgery in experienced hands is low.