Octreotide represses secretory-burst mass and nonpulsatile secretion but does not restore event frequency or orderly GH secretion in acromegaly

Evaluating the Impact of Acromegaly on Quality of Life

Acromegaly has a substantial negative impact on quality of life (QoL). This review aims to discuss the impact of acromegaly on QoL from the clinical perspective as well as from the patient perspective. Furthermore, it aims to evaluate the use of patient-reported outcome measures (PROMs) in acromegaly and how PROMs aid decision-making. The recommendations presented in this review are based on recent clinical evidence on the impact of acromegaly on QoL combined with the authors' own clinical experience treating patients with acromegaly. We recommend that a patient-centered approach should be considered in treatment decisions, integrating conventional biochemical outcomes, tumor control, comorbidities, treatment complications, and PROMs, including QoL measures. This more integrated approach seems effective in treating comorbidities and improving patient-reported outcomes and is critical, as many patients do not achieve biochemical or tumor control and comorbidities, impairment in QoL may not remit even when full biochemical control is achieved.

Biochemical assessment of disease control in acromegaly: reappraisal of the glucose suppression test in somatostatin analogue (SA) treated patients

BACKGROUND

It is recommended not to measure growth hormone during oral glucose suppression (oral glucose tolerance test) during somatostatin analog treatment in acromegaly. However, we have observed that failure to suppress growth hormone in response to oral glucose tolerance test during somatostatin analog unmasks insufficient disease control and hypothesize that somatostatin analog also induces insufficient growth hormone suppression to mixed meals.

METHODS

We therefore compared serum growth hormone levels during two mixed meals in patients with controlled insulin-like growth factor-I levels after either surgery alone (n = 9) or somatostatin analog treatment (n = 9). The patients were unbiasedly matched for gender and insulin-like growth factor-I and studied twice in the following order: (1) during a 6 h growth hormone day curve including two mixed meals and (2) during a 3 h growth hormone profile including 60 min fasting followed by a 2-h oral glucose tolerance test.

RESULTS

During the day curve growth hormone levels were elevated in the somatostatin analog group (P = 0.008) and growth hormone levels 1 h after each meal declined significantly only in the surgery group (P = 0.02). During the oral glucose tolerance test the two groups had similar growth hormone levels prior to the glucose load (P = 0.6), whereas a significant 66% suppression was observed after glucose only in the surgery group (P = 0.001).

CONCLUSIONS

(1) Patients controlled by somatostatin analog fail to suppress growth hormone in response to both mixed meals and oral glucose tolerance test (2) This phenomenon is likely to result in elevated serum growth hormone levels during everyday life in somatostatin analog-treated patients, (3) We postulate that measuring growth hormone levels during oral glucose tolerance test is useful to unmask potential somatostatin analog under-treatment in the presence of 'safe' insulin-like growth factor-I levels.

Bone and Joint Disorders in Acromegaly

Acromegaly is a chronic, progressive disease caused by a growth hormone (GH)-producing pituitary adenoma, resulting in elevated GH and insulin-like growth factor 1 concentrations. Following appropriate therapy (surgery, radiotherapy and/or medical treatment), many systemic GH-induced comorbid conditions improve considerably. Unfortunately, despite biochemical control, acromegaly patients suffer from a high prevalence of late manifestations of transient GH excess, significantly impairing their quality of life. In this overview article, we summarize the pathophysiology, diagnosis, clinical picture, disease course and management of skeletal complications of acromegaly, focusing on vertebral fractures and arthropathy.

Iodide transport and breast cancer

Breast cancer is the second most common cancer worldwide and the leading cause of cancer death in women, with incidence rates that continue to rise. The heterogeneity of the disease makes breast cancer exceptionally difficult to treat, particularly for those patients with triple-negative disease. To address the therapeutic complexity of these tumours, new strategies for diagnosis and treatment are urgently required. The ability of lactating and malignant breast cells to uptake and transport iodide has led to the hypothesis that radioiodide therapy could be a potentially viable treatment for many breast cancer patients. Understanding how iodide is transported, and the factors regulating the expression and function of the proteins responsible for iodide transport, is critical for translating this hypothesis into reality. This review covers the three known iodide transporters - the sodium iodide symporter, pendrin and the sodium-coupled monocarboxylate transporter - and their role in iodide transport in breast cells, along with efforts to manipulate them to increase the potential for radioiodide therapy as a treatment for breast cancer.

Outcome of complications in acromegaly patients after long-term disease remission

Acromegaly patients suffer from pathologically high growth hormone (GH) and IGF-1 levels that in 99% of cases is due to a GH-producing pituitary adenoma. During active disease, GH excess is associated with a number of pathological conditions, such as hypertension, hypertrophic cardiomyopathy, sleep apnea, arthropathy, vertebral fractures and insulin resistance. After adequate treatment in the form of transsphenoidal surgery, radiotherapy, medical treatment or by a combination of these treatment modalities, several comorbid conditions improve considerably. However, despite long-term biochemical disease control, the prevalence of late manifestations of GH excess is high and significantly impair quality of life. In addition, there is evidence that adequate treatment is not able to normalize mortality risk in these patients. In this review, we critically evaluate the long-term consequences of acromegaly after treatment, focusing on comorbid conditions, quality of life and mortality. We also discuss ongoing challenges in the management of acromegaly patients.

Two phenotypes of arthropathy in long-term controlled acromegaly? A comparison between patients with and without joint space narrowing (JSN)

BACKGROUND

Arthropathy is an invalidating complication of acromegaly, also in long-term controlled patients, and is radiographically characterized by osteophytes and preserved joint spaces. However, joint space narrowing (JSN) is observed in the minority of patients. It is unknown whether JSN is the end-stage of acromegalic arthropathy or whether this feature develops independently of acromegaly.

OBJECTIVE

To gain insight into the pathophysiology of acromegalic arthropathy, and, more specifically, in the process of JSN, risk factors for radiographic JSN were studied in a cross-sectional study.

METHODS

We studied hips and knees of 89 well-controlled acromegaly patients (mean age 58.3 yr, 51% female). Joints were divided into two groups based on the presence of JSN, defined as an Osteoarthritis Research Society (OARSI) score ≥ 1. Potential risk factors for JSN were assessed, and its relationship to joint complaints. Individual knees and hips were analyzed in a Generalized Estimating Equations model, adjusted for age, sex, BMI and intra-patient effect.

RESULTS

In controlled acromegaly, JSN was found in, respectively, 10.3% and 15.4% of the hips and knees. Increasing age and female sex were associated with more JSN; acromegaly-specific risk factors for JSN were joint-site specific. In the hip, JSN was related to more active disease: higher pre-treatment GH/IGF-1, longer and more severe GH exposure and immediate postoperative cure was less frequently achieved. In the knee, especially previous knee surgery, not acromegaly-specific characteristics, was associated with JSN. The presence of JSN was associated with more joint complaints.

CONCLUSIONS

JSN is an infrequent finding in patients with acromegalic arthropathy, but it is associated with more symptoms. This study indicates that, at least in the hip, early and ongoing GH/IGF-1 activity play a role in JSN development.

Thyrotropin secretion patterns in health and disease

Thyroid hormones are extremely important for metabolism, development, and growth during the lifetime. The hypothalamo-pituitary-thyroid axis is precisely regulated for these purposes. Much of our knowledge of this hormonal axis is derived from experiments in animals and mutations in man. This review examines the hypothalamo-pituitary-thyroid axis particularly in relation to the regulated 24-hour serum TSH concentration profiles in physiological and pathophysiological conditions, including obesity, primary hypothyroidism, pituitary diseases, psychiatric disorders, and selected neurological diseases. Diurnal TSH rhythms can be analyzed with novel and precise techniques, eg, operator-independent deconvolution and approximate entropy. These approaches provide indirect insight in the regulatory components in pathophysiological conditions.

Effects of previous growth hormone excess and current medical treatment for acromegaly on cognition

BACKGROUND

In untreated acromegaly patients, decreased cognitive functioning is reported to be associated with the degree of growth hormone (GH) and IGF-1 excess. Whether previous GH excess or current medical treatment for acromegaly specifically affects cognition remains unclear. The aim of this study was to compare cognitive functioning of patients who are treated for acromegaly with patients with non-functioning pituitary adenomas (NFA). In addition, we assessed the influence of prolonged medical treatment after initial transsphenoidal surgery on cognition.

DESIGN

In this cross-sectional study, 74 patients participated, who were treated for acromegaly (n = 50; median [interquartile range] age: 53 [45-65] years) or NFA (n = 24; age: 63 [59-70] years). The NFA patients were selected for a high likelihood of normal GH secretion based on an IGF-1 z-score within the normal range (> -2) and zero or one axis substituted. Of the acromegaly patients, 28 had achieved remission, while 22 were biochemically controlled with long-acting somatostatin analogues and/or pegvisomant. Memory and executive functioning were assessed by the 15 Words Test and the Ruff Figural Fluency Test, and reported as z-scores.

RESULTS

The total patient group scored significantly poorer than the reference population on memory and executive functioning (P < 0·001). However, cognitive test performance was not significantly different between acromegaly patients with a persistent disease, acromegaly patients in remission and NFA patients.

CONCLUSION

The total patient group scored worse compared with reference populations. We found no association between previous GH excess and cognition. In addition, current medical treatment for GH excess in acromegaly was not related to memory and executive functioning.

Octreotide long-acting repeatable for acromegaly

Acromegaly remains a therapeutic challenge for the endocrinologist. Among the available therapeutic options, octreotide long-acting repeatable (Sandostatin(®) LAR(®), Novartis) plays a chief role, both as a primary therapy and as an adjuvant treatment after unsuccessful surgery. A plethora of papers and a meta-analysis have demonstrated its efficacy in: control of clinical picture; achievement of safe growth hormone and normal age-matched IGF-I levels (both factors associated with restoration of normal life expectancy) in 60-70% of patients; control of tumor volume (with real shrinkage in over half of cases); and halt or reversal of most acromegaly-associated comorbidities. Treatment is well tolerated in most patients and can be safely prolonged for many years if required.

Quality of life is impaired in association with the need for prolonged postoperative therapy by somatostatin analogs in patients with acromegaly

OBJECTIVE

To assess the influence of long-acting somatostatin analogs (SSTA) after initial pituitary surgery on long-term health-related quality of life (HR-QoL) in relation to disease control in patients with acromegaly.

DESIGN

This is a cross-sectional study in two tertiary referral centers in The Netherlands.

PATIENTS AND METHODS

One hundred and eight patients with acromegaly, in whom transsphenoidal (n=101, 94%) or transcranial (n=7, 6%) surgery was performed. Subsequently, 46 (43%) received additional radiotherapy and 41 (38%) were on postoperative treatment with SSTA because of persistent or recurrent disease at the time of study. All subjects filled in standardized questionnaires measuring HR-QoL. Disease control at the time of study was assessed by local IGF1 SDS.

RESULTS

IGF1 SDS were slightly higher in patients treated with SSTA in comparison with patients without use of SSTA (0.85±1.52 vs 0.25±1.21, P=0.026), but the percentage of patients with insufficient control (IGF1 SDS >2) was not different (17 vs 9%, P=0.208). Patients using SSTA reported poorer scores on most subscales of the RAND-36 and the acromegaly QoL and on all subscales of the multidimensional fatigue inventory-20. A subgroup analysis in patients with similar IGF1 levels (SSTA+, n=26, IGF1 SDS 0.44±0.72 vs SSTA-, n=44, IGF1 SDS 0.41±0.65) revealed worse scores on physical functioning, physical fatigue, reduced activity, vitality, and general health perception across all HR-QoL questionnaires in patients treated with SSTA.

CONCLUSION

QoL is impaired in association with the need for prolonged postoperative therapy by SSTA in patients with acromegaly despite similar IGF1 levels.

Conventional and novel biomarkers of treatment outcome in patients with acromegaly: discordant results after somatostatin analog treatment compared with surgery

CONTEXT

Control of disease activity in acromegaly is critical, but the biochemical definitions remain controversial.

OBJECTIVE

To compare traditional and novel biomarkers and health status in patients with acromegaly treated with either surgery alone or somatostatin analog (SA).

DESIGN AND METHODS

Sixty-three patients in long-term remission based on normalized total IGF1 levels after surgery alone (n=36) or SA (n=27) were studied in a cross-sectional manner. The groups were comparable at diagnosis regarding demographic and biochemical variables. Each subject underwent 3 h of serum sampling including a 2-h oral glucose tolerance test (OGTT). Health status was measured by two questionnaires: EuroQoL and Acrostudy (Patient-assessed-Acromegaly symptom questionnaire (PASQ)).

RESULTS

Total and bioactive IGF1 (μg/l) levels were similar (total: 185 ± 10 (SA) versus 171 ± 8 (surgery) (P=0.28); bioactive: 1.9 ± 0.2 vs 1.9 ± 0.1 (P=0.70)). Suppression of total and free GH (μg/l) during OGTT was blunted in the SA group (total GH(nadir): 0.59 ± 0.08 (SA) versus 0.34 ± 0.06 (surgery) (P=0.01); free GH(nadir): 0.43 ± 0.06 vs 0.19 ± 0.04 (P<0.01)). The insulin response to OGTT was delayed, and the 2-h glucose level was elevated during SA treatment (P=0.02). Disease-specific health status was better in patients after surgery (P=0.02).

CONCLUSIONS

i) Despite similar and normalized IGF1 levels, SA treatment compared with surgery alone was associated with less suppressed GH levels and less symptom relief; ii) this discordance may be due to specific suppression of hepatic IGF1 production by SA; iii) we suggest that biochemical assessment during SA treatment should include both GH and IGF1.

Preoperative lanreotide treatment in acromegalic patients with macroadenomas increases short-term postoperative cure rates: a prospective, randomised trial

OBJECTIVE

To investigate whether 4-month preoperative lanreotide treatment would improve the surgical cure rate of newly diagnosed acromegalic patients with macroadenomas.

DESIGN

A prospective, randomised study.

METHODS

After a baseline evaluation, patients were randomly assigned to 4-month preoperative treatment with lanreotide (starting with 30 mg/2 weeks i.m. and increasing to 30 mg/week i.m. at week 8 if mean GH >2.5 microg/l on GH day curves; pretreatment group, Group 1) or to transsphenoidal surgery (direct surgery group, Group 2). Cure was evaluated 4 months postoperatively primarily by fasting IGF1 less than or equal to age-adjusted upper limit of normal.

RESULTS

A pool of 108 patients was randomly divided into two groups. Five patients in each group were lost to follow-up during the study period, so 49 patients in each group were analysed. At baseline, no difference was observed between the two groups. Cure was established in 24 of 49 (49.0%, 95% confidence interval (CI), 35.0-63.0%) pretreated patients (Group 1) versus 9 of 49 (18.4%, 95% CI, 7.6-29.2%) direct surgery patients (Group 2; P=0.001). Surgical morbidity was recorded in 12 patients (12.2%) and was similar in Group 1 and 2 patients (14.3 and 10.2% respectively; P=0.538). The postoperative hospital stay was similar between groups: being 4.5+/-1.6 days in Group 1 vs 4.8+/-1.9 days in Group 2 (P=0.328).

CONCLUSIONS

Pretreatment with lanreotide before transsphenoidal surgery improves surgical cure rates in patients with GH-secreting pituitary macroadenomas. Pretreatment does not affect surgical complications or duration of hospital stay (ClinicalTrials.gov number, NCT00993356).

Motivations and methods for analyzing pulsatile hormone secretion

Endocrine glands communicate with remote target cells via a mixture of continuous and intermittent signal exchange. Continuous signaling allows slowly varying control, whereas intermittency permits large rapid adjustments. The control systems that mediate such homeostatic corrections operate in a species-, gender-, age-, and context-selective fashion. Significant progress has been made in understanding mechanisms of adaptive interglandular signaling in vivo. Principal goals are to understand the physiological origins, significance, and mechanisms of pulsatile hormone secretion. Key analytical issues are: 1) to quantify the number, size, shape, and uniformity of pulses, nonpulsatile (basal) secretion, and elimination kinetics; 2) to evaluate regulation of the axis as a whole; and 3) to reconstruct dose-response interactions without disrupting hormone connections. This review will focus on the motivations driving and the methodologies used for such analyses.

Somatostatin analog treatment is associated with an increased sleep latency in patients with long-term biochemical remission of acromegaly

BACKGROUND

Somatostatin analogs induce alterations in sleep in healthy adults. Presently, it is unknown whether somatostatin analog treatment affects sleep parameters in patients with acromegaly.

DESIGN

Case-control study.

PATIENTS AND MEASUREMENTS

We assessed sleepiness and sleep patterns in 62 adult patients (32 men, age 61 years (33-88 years) controlled by surgery alone or postoperative radiotherapy (69%), and/or somatostatin analogs (31%). We used two validated sleep questionnaires (Epworth sleepiness score and Münchener chronotype questionnaire). Patient outcomes were compared to controls.

RESULTS

Sleep duration and timing of sleep were not different in patients compared to controls. However, sleepiness score was increased in all patients compared to controls: 6 (1-20) vs. 4 (0-14), P=0.014 (median (range)), reflecting increased daytime sleepiness. Snoring was reported in 68% of both patients and controls (P=0.996), observed apnoea's and restless legs in 23% and 37% of patients compared to 12% and 21% of controls (P=0.062 and P=0.031, resp.). In addition, sleep latency was increased in patients treated by somatostatin analogs compared to patients cured by surgery and/ or radiotherapy (52+/-48 min vs. 26+/-40 min, P=0.005), resulting in a delayed sleep onset (24:08+/-1:26 h vs. 23:25+/-0:43 h, P=0.053). Sleep duration was unaffected.

CONCLUSIONS

Daytime sleepiness is increased in a homogeneous cohort of patients in long-term remission from acromegaly. In addition, somatostatin analog treatment increases sleep latency and delays sleep onset in patients with long-term biochemical control of growth hormone overproduction without altering total sleep duration.

Therapeutic options in the management of acromegaly: focus on lanreotide Autogel

BACKGROUND

In acromegaly, expert surgery is curative in only about 60% of patients. Postoperative radiation therapy is associated with a high incidence of hypopituitarism and its effect on growth hormone (GH) production is slow, so that adjuvant medical treatment becomes of importance in the management of many patients.

OBJECTIVE

To delineate the role of lanreotide in the treatment of acromegaly.

METHODS

Search of Medline, Embase, and Web of Science databases for clinical studies of lanreotide in acromegaly.

RESULTS

Treatment with lanreotide slow release and lanreotide Autogel((R)) normalized GH and insulin-like growth factor-I (IGF-I) concentrations in about 50% of patients. The efficacy of 120 mg lanreotide Autogel((R)) on GH and IGF-I levels was comparable with that of 20 mg octreotide LAR. There were no differences in improvement of cardiac function, decrease in pancreatic beta-cell function, or occurrence of side effects, including cholelithiasis, between octreotide LAR and lanreotide Autogel(R). When postoperative treatment with somatostatin analogs does not result in normalization of serum IGF-I and GH levels after noncurative surgery, pegvisomant alone or in combination with somatostatin analogs can control these levels in a substantial number of patients.

Control of IGF-I levels with titrated dosing of lanreotide Autogel over 48 weeks in patients with acromegaly

BACKGROUND

An essential criterion for control of acromegaly is normalization of IGF-I levels. Somatostatin analogues act to suppress IGF-I and GH levels.

OBJECTIVE

To assess the efficacy and safety of 48 weeks titrated dosing of lanreotide Autogel.

DESIGN

Open-label, multicentre, phase III, 48-week trial.

METHODS

Patients with active acromegaly (IGF-I levels > 1.3 times upper limit of age-adjusted normal range) were recruited. Twelve injections of lanreotide Autogel were given at 28-day intervals: during the 16-week fixed-dose phase, patients received 90 mg; in the 32-week dose-titration phase, patients received 60, 90 or 120 mg according to GH and IGF-I levels. Intention-to-treat analysis was performed to determine the proportion of patients with normalized age-adjusted IGF-I levels at study end. Secondary evaluations included GH levels, clinical acromegaly signs and safety.

RESULTS

Fifty-seven of 63 patients completed the study. Lanreotide Autogel resulted in normalized age-adjusted IGF-I levels in 27 patients (43%, 95% CI 31-55). Mean GH levels decreased from 6.2 to 1.5 microg/l at study end, with 53 of 62 patients (85%) having GH levels < or = 2.5 microg/l (95% CI 76.7-94.3) and 28 of 62 patients (45%) with levels < 1 microg/l (95% CI 32.8-57.6). Twenty-four (38%) had both normal IGF-I levels and GH levels < or = 2.5 microg/l. Acromegaly symptoms reduced significantly in most patients throughout the study. The most common adverse events were gastrointestinal, as expected for somatostatin analogues.

CONCLUSIONS

Using IGF-I as primary end-point, 48 weeks lanreotide Autogel treatment, titrated for optimal hormonal control, controlled IGF-I and GH levels effectively, reduced acromegaly symptoms and was well tolerated.

Impairment of vestibular-mediated cardiovascular response and motor coordination in rats born and reared under hypergravity

It is well known that environmental stimulation is important for the proper development of sensory function. The vestibular system senses gravitational acceleration and then alters cardiovascular and motor functions through reflex pathways. The development of vestibular-mediated cardiovascular and motor functions may depend on the gravitational environment present at birth and during subsequent growth. To examine this hypothesis, arterial pressure (AP) and renal sympathetic nerve activity (RSNA) were monitored during horizontal linear acceleration and performance in a motor coordination task in rats born and reared in 1-G or 2-G environments. Linear acceleration of +/-1 G increased AP and RSNA. These responses were attenuated in rats with a vestibular lesion, suggesting that the vestibular system mediated AP and RSNA responses. These responses were also attenuated in rats born in a 2-G environment. AP and RSNA responses were partially restored in these rats when the hypergravity load was removed, and the rats were maintained in a 1-G environment for 1 wk. The AP response to compressed air, which is mediated independently of the vestibular system, did not change in the 2-G environment. Motor coordination was also impaired in the 2-G environment and remained impaired even after 1 wk of unloading. These results indicate that hypergravity impaired both the vestibulo-cardiovascular reflex and motor coordination. The vestibulo-cardiovascular reflex was only impaired temporarily and partially recovered following 1 wk of unloading. In contrast, motor coordination did not return to normal in response to unloading.

Strong galvanic vestibular stimulation obscures arterial pressure response to gravitational change in conscious rats

Galvanic vestibular stimulation (GVS) is known to create an imbalance in the vestibular inputs; thus it is possible that the simultaneously applied GVS obscures adequate gravity-based inputs to the vestibular organs or modifies an input-output relationship of the vestibular system and then impairs the vestibular-mediated response. To examine this, arterial pressure (AP) response to gravitational change was examined in conscious rats with and without GVS. Free drop-induced microgravity and centrifugation-induced hypergravity were employed to elicit vestibular-mediated AP response. GVS itself induced pressor response in an intensity-dependent manner. This pressor response was completely abolished by vestibular lesion, suggesting that the GVS-induced response was mediated by the vestibular system. The pressor response to microgravity (35 +/- 3 mmHg) was significantly reduced by simultaneously applied GVS (19 +/- 1 mmHg), and pressor response to 3-G load was also significantly reduced by GVS. However, GVS had no effect on air jet-induced pressor response. The effects of GVS on pressor response to gravitational change were qualitatively and quantitatively similar to that caused by the vestibular lesion, effects of which were demonstrated in our previous studies (Gotoh TM, Fujiki N, Matsuda T, Gao S, Morita H. Am J Physiol Regul Integr Comp Physiol 286: R25-R30, 2004; Matsuda T, Gotoh TM, Tanaka K, Gao S, Morita H. Brain Res 1028: 140-147, 2004; Tanaka K, Gotoh TM, Awazu C, Morita H. Neurosci Lett 397: 40-43, 2006). These results indicate that GVS reduced the vestibular-mediated pressor response to gravitational change but has no effect on the non-vestibular-mediated pressor response. Thus GVS might be employed for the acute interruption of the AP response to gravitational change.

Linear acceleration-evoked cardiovascular responses in awake rats

It has been well documented that vestibular-mediated cardiovascular regulation plays an important role in maintaining stable blood pressure (BP) during postural changes. But the underlying neural mechanisms remain to be elucidated. In particular, because the vestibular stimulation employed in previous animal studies activated both semicircular canals and otolith organs, the contributions of the otolith system has not been studied selectively. The goal of the present study was to characterize cardiovascular responses to natural otolith stimulation in awake rats that were subjected to pure linear motion. In any of the four directions tested, transient linear motion produced a short-latency (∼520 ms) increase in mean BP with a peak of 8.27 ± 0.66 mmHg and was followed by a decrease in BP. There was an initial small biphasic response in heart rate (HR) that was followed by a longer duration increase. The short-latency increase in BP was absent in rats that were pentobarbital sodium anesthetized or that were labyrinthectomized bilaterally, but it was unaffected by baroreceptor denervation, indicating that it was of otolith origin. The increase in BP was linear acceleration intensity dependent and was not affected by absence of visual cues. Furthermore, the BP response was attenuated by inactivation of the medial and inferior vestibular nuclei by microinjections of muscimol, indicating that the otolith-driven cardiovascular responses are mediated by the neurons in these areas. These results not only demonstrate the otolith specific influences on the cardiovascular system but also they establish the first rodent model for examining the neural mechanisms underlying the otolith-mediated cardiovascular regulation.

Effect of baroreflex loading on the responsiveness of the vestibulosympathetic reflex in humans

Activation of the vestibular otolith organs with head-down rotation (HDR) increases muscle sympathetic nerve activity (MSNA) in humans. Previously, we demonstrated this vestibulosympathetic reflex (VSR) elicits increases in MSNA during baroreflex unloading (i.e., lower body negative pressure) in humans. Whether such an effect persists during baroreflex loading is unknown. We tested the hypothesis that the ability of the VSR to increase MSNA is preserved during baroreflex unloading and inhibited during baroreflex loading. Ten subjects (26 +/- 1 yr) performed three trials of HDR to activate the VSR. These trials were performed after a period of sustained saline (control), nitroprusside (baroreflex unloading: 0.8-1.0 microg.kg(-1).min(-1)), and phenylephrine (baroreflex loading: 0.6-0.8 microg.kg(-1).min(-1)) infusion. Nitroprusside infusion decreased (Delta7 +/- 1 mmHg, where Delta is change; P < 0.001) and phenylephrine infusion increased mean arterial pressure (Delta8 +/- 1 mmHg; P < 0.001) at rest. HDR performed during the control [Delta3 +/- 2 bursts/min, Delta314 +/- 154 arbitrary units (au) total activity, Delta41 +/- 18% total activity; P < 0.05] and nitroprusside trials [Delta5 +/- 2 bursts/min, Delta713 +/- 241 au total activity, Delta49 +/- 20% total activity; P < 0.05] increased MSNA similarly despite significantly elevated levels at rest (13 +/- 2 to 26 +/- 3 bursts/min) in the latter. In contrast, HDR performed during the phenylephrine trial failed to increase MSNA (Delta0 +/- 1 bursts/min, Delta-15 +/- 33 au total activity, Delta-8 +/- 21% total activity). These results confirm previous findings that the ability of the VSR to increase MSNA is preserved during baroreflex unloading. In contrast, the ability of the VSR to increase MSNA is abolished during baroreflex loading. These results provide further support for the concept that the VSR may act primarily to defend against hypotension in humans.

Attenuated pulse size, disorderly growth hormone and prolactin secretion with preserved nyctohemeral rhythm distinguish irradiated from surgically treated acromegaly patients

BACKGROUND

Radiation induces time-dependent loss of anterior pituitary function, attributed to damage of the pituitary gland and hypothalamic centres. The development of growth hormone deficiency (GHD) in irradiated acromegaly patients is not well defined.

OBJECTIVE

Detailed analysis of spontaneous 24-h GH and prolactin (PRL) secretion in relation to other pituitary functions and serum IGF-I concentrations in an attempt to find criteria for GHD in acromegalic patients with a GH response < 3 microg/l during the insulin tolerance test (ITT).

DESIGN

Plasma hormone profiles obtained by 10 min sampling for 24 h in postoperatively irradiated acromegalic patients, compared with patients cured by surgery only and matched healthy controls.

SETTING/PARTICIPANTS

University setting. Fifteen subjects in each group.

OUTCOME MEASURES

GH and PRL secretory parameters quantified by deconvolution, cluster, cosinor and approximate entropy (ApEn) analyses, IGF-I concentrations.

RESULTS

Irradiation attenuated pulsatile secretion of GH and PRL, but total PRL secretion was unchanged. GH and PRL secretory regularity were diminished. Circadian timing remained intact. Pulsatile GH secretion and IGF-I were correlated (R = 0.30, P = 0.04). Criteria of pulsatile GH secretion = 12 microg/l/24 h and ApEn = 0.800 separated 12 of 15 irradiated patients from all others.

CONCLUSION

Irradiated acromegaly patients with a subnormal GH response to ITT have very limited spontaneous GH secretion, with specific attenuation of the size of GH bursts and a highly irregular pattern, but with retained diurnal properties. These patients are thus likely GH-deficient and might benefit from GH replacement.

Acromegaly caused by growth hormone-releasing hormone-producing tumors: long-term observational studies in three patients

We report on three newly diagnosed patients with extracranial ectopic GHRH-associated acromegaly with long-term follow-up after surgery of the primary tumor. One patient with a pancreatic tumor and two parathyroid adenomas was the index case of a large kindred of MEN-I syndrome. The other two patients had a large bronchial carcinoid. The first patient is still in remission now almost 22 years after surgery. In the two other patients GHRH did not normalize completely after surgery and they are now treated with slow-release octreotide. IGF-I normalized in all patients. During medical treatment basal GH secretion remained (slightly) elevated and secretory regularity was decreased in 24 h blood sampling studies. We did not observe development of tachyphylaxis towards the drug or radiological evidence of (growing) metastases. We propose life-long suppressive therapy with somatostatin analogs in cases with persisting elevated serum GHRH concentrations after removal of the primary tumor. Independent parameters of residual disease are elevated basal (nonpulsatile) GH secretion and decreased GH secretory regularity.

Effects of postural changes and removal of vestibular inputs on blood flow to the head of conscious felines

Prior studies have shown that removal of vestibular inputs produces lability in blood pressure during orthostatic challenges (Holmes MJ, Cotter LA, Arendt HE, Cass SP, and Yates BJ. Brain Res 938: 62-72, 2002; Jian BJ, Cotter LA, Emanuel BA, Cass SP, and Yates BJ. J Appl Physiol 86: 1552-1560, 1999). Furthermore, these studies led to the prediction that the blood pressure instability results in susceptibility for orthostatic intolerance. The present experiments tested this hypothesis by recording common carotid blood flow (CCBF) in conscious cats during head-up tilts of 20, 40, and 60 degrees amplitudes, before and after the surgical elimination of labyrinthine inputs through a bilateral vestibular neurectomy. Before vestibular lesions in most animals, CCBF remained stable during head-up rotations. Unexpectedly, in five of six animals, the vestibular neurectomy resulted in a significant increase in baseline CCBF, particularly when the laboratory was illuminated; on average, basal blood flow measured when the animals were in the prone position was 41 +/- 17 (SE) % higher after the first week after the lesions. As a result, even when posturally related lability in CCBF occurred after removal of vestibular inputs, blood supply to the head was not lower than when labyrinthine inputs were present. These data suggest that vestibular influences on cardiovascular regulation are more complex than previously appreciated, because labyrinthine signals appear to participate in setting basal rates of blood flow to the head in addition to triggering dynamic changes in the circulation to compensate for orthostatic challenges.

Persistent diastolic dysfunction despite successful long-term octreotide treatment in acromegaly

INTRODUCTION

This study was designed to evaluate potential reversibility of left-ventricular (LV) dysfunction in patients with acromegaly following long-term control of disease. It is unknown whether the cardiac changes induced by acromegaly can be reversed completely by long-term strict control of growth hormone excess by octreotide.

PATIENTS AND METHODS

We compared LV systolic and diastolic function in inactive patients with acromegaly (n = 22), who were divided into patients with long-term control by octreotide (n = 14) and patients with long-term cure by surgery/radiotherapy (n = 8). We also assessed these parameters in patients with active acromegaly (n = 17).

RESULTS

In patients with active acromegaly, systolic function at rest was decreased by 18% (P < 0.01), LV mass index increased by 40% (P < 0.04) and isovolumetric relaxation time increased by 19% (P < 0.01), compared with patients with inactive acromegaly. These parameters were not different between well-controlled and cured patients. Using tissue Doppler imaging, the ratio between early and late diastolic velocity (E'/A' ratio) was decreased in active, compared with inactive acromegaly (0.75+/-0.07 versus 1.24+/-0.15; P < 0.01). This E'/A' ratio was considerably higher in cured, compared with octreotide-treated, patients (1.75+/-0.41 versus 1.05+/-0.1; P < 0.01).

CONCLUSION

Diastolic function is persistently and significantly more impaired in acromegalic patients with long-term control by octreotide than in surgically cured patients, which points to biological effects of subtle abnormalities in growth hormone secretion. Criteria for strict biochemical control of acromegaly should thus be reconsidered.

Intravenous octreotide test predicts the long term outcome of treatment with octreotide-long-acting repeatable in active acromegaly

OBJECTIVE

Depot formulations of somatostatin analogues are increasingly used in the treatment of active acromegaly. A priori knowledge of the efficacy of these drugs in controlling GH excess is clinically relevant, because only approximately 60% of the patients respond with adequate control of GH (GH levels < 5 mU/L) and/or IGF-1 levels upon this treatment. Therefore, we assessed the acute responses of serum GH levels to a new octreotide test (intravenous administration of 50 microg) in 98 consecutive patients with active acromegaly and we measured the predictive value of this test for the efficacy of chronic octreotide-long acting repeatable (octreotide-LAR) treatment in 18 patients.

DESIGN

Serum GH concentrations were measured before and at 20, 30, 45, 60, 90, 120, 150 and 180 min following 50 microg i.v. octreotide. The minimal achieved GH was used for analysis. Octreotide-LAR was individually titrated aiming at a normal serum IGF-I for age and a serum GH < 5 mU/L. The mean of 3-6 monthly serum GH and IGF-I measurements after individual dose adjustment was used for evaluating the efficacy of chronic therapy.

RESULTS

Octreotide decreased GH levels to values below 5 mU/L in only 49% of unselected consecutive patients and the response was inversely related to basal GH levels. In patients with baseline GH above 50 mU/L, 50 microg i.v. octreotide reduced GH to < 5 mU/L in only 15% of cases (n = 41), whereas in patients with baseline GH levels below 50 mU/L this goal was achieved in 77% of cases. The fractional decrease in GH levels upon octreotide injection was similar in microadenomas and macroadenomas. The minimally achieved serum GH concentration during the intravenous octreotide test was a good predictor for the GH concentrations during long-term octreotide-LAR treatment as assessed in 18 patients. The intravenous octreotide test, using a minimal GH level of < 5 mU/L, had a sensitivity, positive and negative predictive value of 100% for prediction of GH suppression to below 5 mU/L during long term octreotide-LAR treatment. For predicting the response of IGF-I during long-term treatment, the test performed with a sensitivity of 73% and a positive predictive value of 73%.

CONCLUSION

Intravenous octreotide reduces GH to concentrations < 5 mU/L in approximately 50% of consecutive patients with active acromegaly, which predicts a good response to chronic octreotide-LAR treatment.

Irregular and frequent cortisol secretory episodes with preserved diurnal rhythmicity in primary adrenal Cushing's syndrome

To evaluate the pathophysiology of altered cortisol secretion in patients with primary adrenal hypercortisolism, cortisol secretion was investigated in 12 patients, seven with a unilateral adenoma and five with ACTH-independent macronodular adrenal hyperplasia compared with age- and gender-matched controls and with patients with pituitary-dependent hypercortisolism. Pulsatile secretion was increased 2-fold (P = 0.04), attributable to increased event frequency (P = 0.002). All patients showed a significant diurnal rhythm with a delay in phase shift of 3 h (P = 0.01). Approximate entropy ratio, a feedback-sensitive measure, was increased compared with controls (P = 0.00003) but similar to that of pituitary-dependent hypercortisolism (P = 0.77), denoting loss of autoregulation. Cortisol burst-mass tended to be smaller in patients with ACTH-independent macronodular adrenal hyperplasia than in unilateral adenoma (P = 0.06). In conclusion, increased cortisol secretion in patients with primary adrenal Cushing's syndrome is caused by amplified pulsatile secretion via event frequency modulation. We speculate that partial preservation of secretory regularity and diurnal rhythmicity point to incomplete autonomy of these tumors.

Effects of bilateral vestibular nucleus lesions on cardiovascular regulation in conscious cats

The vestibular system participates in cardiovascular regulation during postural changes. In prior studies (Holmes MJ, Cotter LA, Arendt HE, Cas SP, and Yates BJ. Brain Res 938: 62-72, 2002, and Jian BJ, Cotter LA, Emanuel BA, Cass SP, and Yates BJ. J Appl Physiol 86: 1552-1560, 1999), transection of the vestibular nerves resulted in instability in blood pressure during nose-up body tilts, particularly when no visual information reflecting body position in space was available. However, recovery of orthostatic tolerance occurred within 1 wk, presumably because the vestibular nuclei integrate a variety of sensory inputs reflecting body location. The present study tested the hypothesis that lesions of the vestibular nuclei result in persistent cardiovascular deficits during orthostatic challenges. Blood pressure and heart rate were monitored in five conscious cats during nose-up tilts of varying amplitude, both before and after chemical lesions of the vestibular nuclei. Before lesions, blood pressure remained relatively stable during tilts. In all animals, the blood pressure responses to nose-up tilts were altered by damage to the medial and inferior vestibular nuclei; these effects were noted both when animals were tested in the presence and absence of visual feedback. In four of the five animals, the lesions also resulted in augmented heart rate increases from baseline values during 60 degrees nose-up tilts. These effects persisted for longer than 1 wk, but they gradually resolved over time, except in the animal with the worst deficits. These observations suggest that recovery of compensatory cardiovascular responses after loss of vestibular inputs is accomplished at least in part through plastic changes in the vestibular nuclei and the enhancement of the ability of vestibular nucleus neurons to discriminate body position in space by employing nonlabyrinthine signals.

Centrally Applied Somatostatin Inhibits the Estrogen-Induced Luteinizing Hormone Surge via Hypothalamic Gonadotropin-Releasing Hormone Cell Activation in Female Rats1

Overexpression of growth hormone (GH) as well as GH-deficiency dramatically impairs reproductive function. Decreased reproductive function as a result of altered GH release is, at least partially, due to changes at the hypothalamic-pituitary level. We hypothesize that hypothalamic somatostatin (SOM), the inhibiting factor of GH release from the pituitary, may play a central role in the "crosstalk" between the somatotropic and gonadotropic axes. In the present study we investigated the possible effects of a centrally applied SOM analog on the LH surge and the concurrent activation of hypothalamic GnRH neurons in female rats. To this end, female rats were treated with estradiol 2 wk after ovariectomy and were given a single central injection with either the SOM analog, octreotide, or saline just prior to surge onset, after which hourly blood samples were taken to measure LH. Two weeks later, the experimental setup was randomly repeated to collect brains during the anticipated ascending phase of the LH surge. Vibratome sections were subsequently double-stained for GnRH and cFos peptide. Following octreotide treatment, LH surges were significantly attenuated compared to those in saline-treated control females. Also, octreotide treatment significantly decreased the activation of hypothalamic GnRH neurons. These results clearly demonstrate that SOM is able to inhibit LH release, at least in part by decreasing the activation of GnRH neurons. Based on these results, we hypothesize that hypothalamic SOM may be critically involved in the physiological regulation of the proestrus LH surge.

Diminished baroreflex control of heart rate responses in otoconia-deficient C57BL/6JEi head tilt mice

The maintenance of stable blood pressure during postural changes is known to involve integration of vestibular and cardiovascular central regulatory mechanisms. Sensory activity in the vestibular system plays an important role in cardiovascular regulation. The purpose of this study was to determine the role of vestibular gravity receptors in normal baroreflex function. Baroreflex heart rate (HR) responses to changes in blood pressure (BP) in otoconia-deficient head tilt (het) mice (n = 8) were compared with their wild-type littermates (n = 12). The study was carried out in conscious male mice chronically implanted with arterial and venous catheters for recording BP and HR and for the infusion of vasoactive drugs. Resting HR was higher in the het mice (661 +/- 13 beats/min) than in the wild-type mice (579 +/- 20 beats/min). BP was comparable in the het (113 +/- 4 mmHg) and wild-type mice (104 +/- 4 mmHg). The slopes of reflex decreases in HR in response to phenylephrine (PE) were blunted in the het mice (-5.5 +/- 1.5 beats x min(-1) x mmHg(-1)) compared with the wild-type mice (-8.5 +/- 0.9 beats x min(-1) x mmHg(-1)). Likewise, reflex tachycardic responses to decreases in BP with sodium nitroprusside (SNP) were significantly blunted in the het mice (-0.8 +/- 0.3 beats x min(-1) x mmHg(-1)) versus the wild-type mice (-2.2 +/- 0.6 beats x min(-1) x mmHg(-1)). Frequency-domain analysis of the HR variability suggests that under resting conditions, parasympathetic contribution was lower in the het versus wild-type mice. Mapping of the expression of immediate-early gene product, c-Fos, in forebrain and brain stem nuclei in response to a BP challenge showed no differences between the wild-type and het mice. These results suggest that tonic activity of gravity receptors modulates and is required for normal function of the cardiac baroreflexes.

Acute hemodynamic responses in the head during microgravity induced by free drop in anesthetized rats

To examine acute hemodynamic responses to microgravity (μG) in the head, we measured carotid artery pressure (CAP) and jugular vein pressure (JVP) to calculate cephalic perfusion pressure (CPP = CAP − JVP) and recorded images of microvessels in the iris to evaluate capillary blood flow velocity (CBFV) and capillary diameter (CD) in anesthetized rats during 4.5 s of μG induced by free drop. Rats were placed in 30° head-up whole body-tilted (HU, n = 7) or horizontal (flat, n = 6) position. In the flat group, none of the measured variables was significantly affected by μG, whereas in the HU group, CAP, JVP, and CPP increased, respectively, by 23.4 ± 2.6, 1.3 ± 0.2, and 22.9 ± 3.1 mmHg, and CBFV and CD increased, respectively, by 33 ± 8 and 9 ± 3%, showing an increase in capillary blood flow. To further examine the mechanisms underlying these CAP and JVP increases, another experiment was performed in which CAP and JVP were measured in anesthetized rats ( n = 6) during a postural change from HU to flat. In these animals, the change in JVP was similar to that observed during actual μG, but no change in CAP was seen, indicating that the JVP increase during actual μG is caused by disappearance of the gravitational pressure gradient in the head-to-foot axis, whereas the CAP increase is not. In conclusion, actual μG elicits an increase in CPP due to a greater increase in CAP than JVP, resulting in increased capillary blood flow. Although the increase in JVP is explained by the disappearance of gravitational pressure gradient in the head-to-foot axis as a result of μG, the larger increase in CAP is not.