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

Early Predictors of Remission in Acromegaly Patients after Pure Endoscopic Endonasal Transsphenoidal Surgery

Objective Surgery is the first-line treatment in acromegaly but it takes months to confirm remission. It is crucial to determine remission early in order to inform the patient and plan further treatment options. We aimed to evaluate the predictors of remission at the early phase after endoscopic endonasal pituitary surgery in acromegaly patients.

Methods Fifty-four growth hormone (GH)-adenoma patients operated via pure endoscopic endonasal approach were analyzed in this observational study. We compared the basic clinical, radiological characteristics, and the preoperative and postoperative hormone levels in terms of remission according to current guidelines.

Results The surgical remission rate was 61.1%. When the patients were compared according to surgical remission, the age, gender, and immunohistochemical granulation type were found to be nonsignificant, while diabetes mellitus was more common (55.6 vs. 44.4%). The preoperative tumor volume (1.2 ± 0.9 vs. 4.1 ± 4.2 cm3) and postoperative GH and insulin-like growth factor-1 (IGF-1) levels were higher in the nonremission group (p < 0.05). We defined a number of cut-off values of both GH and IGF-1 levels to predict remission at the postoperative phase. Age standardized regression analyses showed that postoperative day 1 (POD-1) GH levels (odds ratio [OR]: 8.9; 95% confidence interval [CI]: 1.99–40.0, p = 0.004) and tumor volume (OR: 3.14; 95% CI: 1.09–9.0, p = 0.034) were found to be significant independent predictors for remission.

Conclusion We demonstrated that tumor volume and POD-1 GH levels are independent predictors of remission in acromegaly patients operated via the pure endoscopic endonasal technique and may be used as an early marker of remission, and this may lead to taking adjuvant medical therapies early into account to improve prognosis.

Secondary diabetes mellitus in acromegaly

Secondary diabetes mellitus (DM) is a common complication of acromegaly, encountered in up to 55% of cases. Vice versa, the prevalence of acromegaly is markedly higher in cohorts of patients with type 2 DM (T2DM). The presence of secondary DM depends primarily on acromegaly status and is associated with increased cardiovascular morbidity, malignancy rate and overall mortality. The principal pathophysiologic mechanism is increased insulin resistance due to excessive lipolysis and altered fat distribution, reflected at the presence of intermuscular fat and attenuated, dysfunctional adipose tissue. Insulin resistance is ascribed to the direct, diabetogenic effects of growth hormone (GH), which prevail over the insulin-sensitizing effects of insulin-like growth factor 1 (IGF-1), probably due to higher glucometabolic potency of GH, IGF-1 resistance, or both. Inversely, GH and IGF-1 act synergistically in increasing insulin secretion. Hyperinsulinemia in portal vein leads to enhanced responsiveness of liver GH receptors and IGF-1 production, pointing towards a mutually amplifying loop between GH-IGF-1 axis and insulin. Secondary DM occurs upon beta cell exhaustion, principally due to gluco-lipo-toxicity. Somatostatin analogues inhibit insulin secretion; especially pasireotide (PASI) impairs glycaemic profile in up to 75% of cases, establishing a separate pathophysiologic entity, PASI-induced DM. In contrast, pegvisomant and dopamine agonizts improve insulin sensitivity. In turn, metformin, pioglitazone and sodium-glucose transporters 2 inhibitors might be disease-modifying by counteracting hyperinsulinemia or acting pleiotropically. Large, prospective cohort studies are needed to validate the above notions and define optimal DM management in 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.

The influence of type 2 diabetes on serum GH and IGF-I levels in hospitalized Japanese patients

OBJECTIVE

Although serum insulin like growth factor type 1 (IGF-I) levels are negatively correlated with hemoglobin A1c (HbA1c) in patients with type 1 diabetes, this correlation is controversial in patients with type 2 diabetes mellitus (T2DM) because of the influence of multiple factors including insulin secretion and obesity. The aim of this study was to evaluate the influence of T2DM on serum growth hormone (GH) and IGF-I levels in Japanese patients, who exhibited relatively low BMI compared with white patients in the previous studies.

DESIGN

We retrospectively analysed 315 consecutive Japanese hospitalized patients with T2DM. We analysed factors correlated with changes in serum IGF-I levels and those related to diabetes.

RESULTS

The median HbA1c was 8.7% (7.4-10.2) and the median body mass index (BMI) was 26.2kg/m(2) (23.1-29.7), which was relatively low compared with the previous studies. Overall, no correlations was found between serum GH or IGF-I levels and fasting plasma glucose (FPG) or HbA1c; however, when stratified by FPG and HbA1c levels, serum IGF-I levels were significantly lower in patients with FPG≥200mg/dL than in those with FPG<200mg/dL (p=0.039). In addition, serum IGF-I levels were significantly lower in patients with HbA1c≥12% than in those with HbA1c<12% (p=0.046). Multiple linear regression analysis revealed a positive correlation between fasting C-peptide levels and serum IGF-I levels (p=0.040), whereas no correlations was found for BMI, duration of T2DM, FPG levels, or HbA1c. Moreover, patients with improved HbA1c levels during the follow up period showed a significant increase in serum IGF-I levels.

CONCLUSIONS

Serum IGF-I levels were significantly decreased in Japanese patients with uncontrolled T2DM, and impaired insulin secretion may be a mechanism underlying this effect. When diagnosing acromegaly in patients with uncontrolled diabetes, these factors should be taken into account.

Current and Emerging Aspects of Diabetes Mellitus in Acromegaly

Diabetes mellitus is a frequent complication of acromegaly, a disease characterized by chronic hypersecretion of growth hormone (GH) by a pituitary adenoma. Diabetes occurs commonly but not only as a consequence of an insulin-resistant state induced by GH excess. The development of diabetes in patients with acromegaly is clinically relevant, since such a complication is thought to increase the already elevated cardiovascular morbidity and mortality risk of the disease. Emerging data suggest that a specific cardiomyopathy can be identified in acromegaly patients with diabetes. Moreover, the presence of diabetes may also influence therapeutic decision making in acromegaly, since traditional and newly developed drugs used in this clinical setting may impact glucose metabolism regardless of control of GH hypersecretion.

Acromegaly with Normal Insulin-Like Growth Factor-1 Levels and Congestive Heart Failure as the First Clinical Manifestation

The leading cause of morbidity and mortality in patients with acromegaly is cardiovascular complications. Myocardial exposure to excessive growth hormone can cause ventricular hypertrophy, hypertension, arrhythmia, and diastolic dysfunction. However, congestive heart failure as a result of systolic dysfunction is observed only rarely in patients with acromegaly. Most cases of acromegaly exhibit high levels of serum insulin-like growth factor-1 (IGF-1). Acromegaly with normal IGF-1 levels is rare and difficult to diagnose. Here, we report a rare case of an acromegalic patient whose first clinical manifestation was severe congestive heart failure, despite normal IGF-1 levels. We diagnosed acromegaly using a glucose-loading growth hormone suppression test. Cardiac function and myocardial hypertrophy improved 6 months after transsphenoidal resection of a pituitary adenoma.

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.

Hypothyroidism associated with acromegaly and insulin-resistant diabetes mellitus in a Samoyed

BACKGROUND

The aetiology of insulin resistance (IR) in naturally occurring canine hypothyroidism is poorly understood and likely multifactorial. Excess secretion of growth hormone (GH) by transdifferentiated pituitary cells may contribute to IR in some hypothyroid dogs, but although this has been demonstrated in experimental studies, it has not yet been documented in clinical cases.

CASE REPORT

A 4-year-old male entire Samoyed presented with an 8-month history of pedal hyperkeratosis and shifting lameness, which had been unresponsive to zinc supplementation, antibiotics and glucocorticoid therapy. The dog also exhibited exercise intolerance and polydipsia of 12 and 2 months duration, respectively. On physical examination, obesity, poor coat condition, widened interdental spaces and mild respiratory stridor were noted. Initial laboratory test results revealed concurrent hypothyroidism and diabetes mellitus (DM). Further investigations showed IR, GH excess and a paradoxical increase of GH following stimulation with thyrotropin-releasing hormone.

CONCLUSIONS

To the authors' knowledge, this is the first reported case that suggests that GH alterations may have clinical significance in naturally occurring hypothyroidism. Among other factors, hypothyroidism-induced GH excess should be considered as a possible cause of IR in patients suffering from hypothyroidism and concurrent DM. In such cases, DM may reverse with treatment of hypothyroidism, as was documented in this case.

What the mind knows but the eyes may still miss: reducing the 'Acromegalic Window'

A 46-year-old Asian man was referred to our endocrine unit (April 2013) by his general practitioner for investigation of a neck mass. Ultrasound scan of the neck and serum thyroid-stimulating hormone levels revealed a euthyroid multinodular goitre. He presented with symptoms of frequent headaches, polydypsia, polyuria, perspiration and night sweats and demonstrated classic physical features of acromegaly. In retrospect, the patient's medical history included encounters with numerous physicians from an array of specialties for over 20 years, mostly for symptoms well recognised to be attributed to growth hormone (GH) excess. Random insulin-like growth factor-1 level was elevated at 103 nmol/L (normal 13-37 nmol/L) and oral glucose tolerance test showed non-suppressible GH secretion (15.06 mIU/L at 120 min). MRI revealed a mildly enlarged pituitary gland. The patient has been referred for surgery. This case highlights that, even with classic features of acromegaly, there may be a wide-ranging 'Acromegalic Window' between first presentation and clinical suspicion to eventual diagnosis.

[Biomarkers in endocrinology]

TSH assay is the best parameter of the thyroid function. For adults, the normal interval of TSH concentrations range from 0.4 to 4 mUI/L. At the first trimester of pregnancy, TSH levels must be <2.5 mUI/L. Normal TSH levels increase with aging and obesity. The biological diagnosis relies on the identification of excessive secretion of the metanephrines which are more sensitive and specific than those of catecholamines. The concentrations of the free plasmatic metanephrines reflect the ongoing production of tumor. Plasma methoxytyramine is a novel biomarker of metastatic pheochromocytomas and paragangliomas. Serum IGF1 is a reliable measure of integrated GH concentrations in patients with acromegaly. Accurate assessment of IGF1 concentrations requires age and sex-matched control values. IGF1 is a sensitive tool for the diagnosis of acromegaly and efficacy of therapies. Serum AMH assay is more sensitive, more specific and more reproducible that counting of ovarian follicles by ultrasound. AMH level above 5 ng/mL (35 pmol/L) could be chosen as one of the diagnostic criteria for the polycystic ovary syndrome. In early or "incipiens" ovarian failure, the decrease in serum AMH is far ahead of the increase in FSH. Thyroglobulin (TG) and calcitonin (CT) are the sensitive and specific markers of respectively well-differentiated thyroid cancers of follicular origin and of the medullary thyroid cancers. The same tumour marker assay should be used to monitor a given patient. Chromogranin A (CgA) is a highly efficient biomarker for diagnosis and follow-up of various endocrine tumours. Despite the lack of international standardisation, some CgA assays are reliable.

Frequency of acromegaly in adults with diabetes or glucose intolerance and estimated prevalence in the general population

The objective of this study was to evaluate the frequency of acromegaly in adults with diabetes mellitus (DM) or glucose intolerance (GI) and to estimate its prevalence in the general population. A total of 2,270 patients with DM or GI and age from 20 to 70 years were studied. Patients with known pituitary disease and pregnant women were excluded. Serum IGF-1 was measured in all subjects and, if elevated, a new measurement was obtained together with the measurement of GH in the oral glucose tolerance test (OGTT). Patients with persistently elevated IGF-1 and inadequate suppression of GH were submitted to magnetic resonance imaging (MRI). Acromegaly was not suspected by the assistant physician in any of the patients. Six patients had persistently elevated IGF-1 and inadequate suppression of GH in the OGTT (without other conditions associated with GH or IGF-1 elevation). Pituitary adenoma was detected by MRI in three patients, and two subjects presented an acromegalic phenotype. Two patients were submitted to transsphenoidal surgery, with immunohistochemistry confirming immunoreactivity for GH. Another patient was treated with octreotide LAR which resulted in the normalization of IGF-1 and GH. Considering a prevalence of DM or GI of 20% in adults and the occurrence of these co-morbidities in 55% of patients with acromegaly, the frequency of 3/2,270 found in this study permits to estimate 480 cases/1,000,000 adults. The present results suggest that the prevalence of acromegaly is underestimated and further studies are needed to evaluate the cost-effectiveness of biochemical screening in certain groups of patients.

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.

The utility of oral glucose tolerance testing for diagnosis and assessment of treatment outcomes in 166 patients with acromegaly

CONTEXT

GH suppression after oral glucose load [oral glucose tolerance test (OGTT)] and normal age- and gender-matched IGF-I levels reflect biochemical control of acromegaly. The OGTT is the gold standard for determining control of GH secretion at diagnosis and after surgical treatment, but the usefulness of performing an OGTT in patients treated with medical therapy has not been determined.

OBJECTIVE

Our objective was to assess relationships between basal GH levels (basal GH), GH responses to OGTT [GH nadir (GHn)], and IGF-I levels.

DESIGN

This was a retrospective electronic database review.

SETTING

This study was performed at a tertiary outpatient pituitary center.

PATIENTS

A total of 166 patients with acromegaly (79 females, 87 males) were included in the study. Four categories of testing were performed: diagnosis, postoperative assessment without medication, testing during somatostatin analog (SA) therapy, and testing during dopamine agonist (DA) therapy.

MAIN OUTCOME MEASURES

Basal serum GH and IGF-I levels and GH levels 2 h after 75 g OGTT were measured.

RESULTS

A total of 482 simultaneous OGTT and IGF-I measurements were observed from 1985--2008. Discordant results of oral glucose tolerance testing (GHn and IGF-I) were observed 33, 48, and 18% in postoperative assessment without medication, SA, and DA categories, respectively. In the SA category, 42% of tests were discordant with normal IGF-I and nonsuppressed GHn. In contrast, 4% of tests were discordant with normal IGF-I and nonsuppressed GH in those treated with DA. No significant differences in discordance were observed when basal GH was used.

CONCLUSIONS

Both basal and GHn levels are highly discordant with IGF-I levels during medical therapy with SAs. The OGTT is not useful in assessing biochemical control in these subjects.

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.