Sympathovagal imbalance in acromegalic patients

Heart Rate Variability Applications in Medical Specialties: A Narrative Review

HRV is clinically considered to be a surrogate measure of the asymmetrical interplay of the sympathetic and parasympathetic nervous system. While HRV has become an increasingly measured variable through commercially-available wearable devices, HRV is not routinely monitored or utilized in healthcare settings at this time. The purpose of this narrative review is to discuss and evaluate the current research and potential future applications of HRV in several medical specialties, including critical care, cardiology, pulmonology, nephrology, gastroenterology, endocrinology, infectious disease, hematology and oncology, neurology and rehabilitation, sports medicine, surgery and anesthesiology, rheumatology and chronic pain, obstetrics and gynecology, pediatrics, and psychiatry/psychology. A narrative literature review was conducted with search terms including HRV and relevant terminology to the medical specialty in question. While HRV has demonstrated promise for some diagnoses as a non-invasive, easy to use, and cost-effective metric for early disease detection, prognosis and mortality prediction, disease monitoring, and biofeedback therapy, several issues plague the current literature. Substantial heterogeneity exists in the current HRV literature which limits its applicability in clinical practice. However, applications of HRV in psychiatry, critical care, and in specific chronic diseases demonstrate sufficient evidence to warrant clinical application regardless of the surmountable research issues. More data is needed to understand the exact impact of standardizing HRV monitoring and treatment protocols on patient outcomes in each of the clinical contexts discussed in this paper.

The Heart's Function as a Pump Assessed via Impedance Cardiography and the Autonomic System Balance in Patients with Early-Stage Acromegaly

BACKGROUND

Acromegaly is a rare, chronic disease that involves structural and functional abnormalities of the cardiovascular system. Acromegaly likely affects interactions between the cardiovascular system and the autonomic nervous system (ANS). Therefore, assessing the relationship between sympathetic-parasympathetic balance by analyzing heart rate variability (HRV) and the hemodynamic profile via impedance cardiography (ICG) may be useful in learning the exact nature of interactions between the ANS and the cardiovascular system. The purpose of this study was to assess a possible association between HRV and ICG-based parameters of cardiac function in patients newly diagnosed with acromegaly.

METHODS

This observational cohort study was conducted on 33 patients (18 men, mean age of 47 years) newly diagnosed with acromegaly and no significant comorbidities. A correlation analysis (Spearman's rank coefficient R) of the parameters assessed via ICG and the HRV assessed via 24 h ambulatory electrocardiography was performed. ICG assessments included the following parameters: stroke volume index (SI), cardiac index (CI), acceleration index (ACI), velocity index (VI), and Heather index (HI). The analysis of HRV included both time-domain parameters (pNN50, SDNN, SDSD, rMSSD) and frequency-domain parameters (total power (TP) and its individual frequency bands: low-frequency (LF day/night), high-frequency (HF day/night), and the LF/HF ratio (day/night)).

RESULTS

Frequency-domain HRV analysis showed the following correlations: (1) lower nighttime LF values with higher ACI (R = -0.38; p = 0.027) and HI (R = -0.46; p = 0.007) values; (2) higher nighttime HF values with higher ACI (R = 0.39; p = 0.027) and HI (R = 0.43; p = 0.014) values; (3) lower nighttime LF/HF values with higher ACI (R = -0.36; p = 0.037) and HI (R = -0.42; p = 0.014) values; (4) higher nighttime TP values with higher SI values (R = 0.35; p = 0.049). Time-domain parameters of HRV showed a significant correlation only between the nighttime values of SDSD and SI (R = 0.35; p = 0.049) and between the daytime and nighttime values of SDNN and HR (R = -0.50; p = 0.003 and R = -0.35; p = 0.046). In multivariate regression, only ACI was revealed to be independently related to HRV.

CONCLUSIONS

In patients newly diagnosed with acromegaly, the relationship between the sympathetic-parasympathetic balance assessed via HRV and the hemodynamic profile assessed via ICG was revealed. Better function of the left ventricle was associated with a parasympathetic shift in the autonomic balance.

The Effect and Potential Mechanism Analysis of Growth Hormone-Secreting Pituitary Adenomas on Thyroid Function

OBJECTIVE

Current studies on the effect of high growth hormone (GH)/insulin-like growth factor (IGF)-1 on thyroid function are inconsistent. The aim was to explore the effect and potential mechanism of high GH/IGF-1 on thyroid function by analyzing the changes of thyroid function in patients with growth hormone-secreting pituitary adenoma (GHPA).

METHODS

This was a retrospective cross-sectional study. Demographic and clinical data of 351 patients with GHPA who were first admitted to Beijing Tiantan Hospital, Capital Medical University, from 2015 to 2022 were collected to analyze the relationship between high GH/IGF-1 levels and thyroid function.

RESULTS

GH was negatively correlated with total thyroxine (TT4), free thyroxine (FT4), and thyroid-stimulating hormone (TSH). IGF-1 was positively correlated with total triiodothyronine (TT3), free triiodothyronine (FT3), and FT4 and negatively correlated with TSH. Insulin-like growth factor-binding protein (IGFBP)-3 was positively correlated with TT3, FT3, and FT3:FT4 ratio. The FT3, TT3, TSH, and FT3:FT4 ratio of patients with GHPA and diabetes mellitus (DM) were significantly lower than those with GHPA but without DM. With the increase of tumor volume, thyroid function gradually decreased. GH and IGF-1 were correlated negatively with age in patients with GHPA.

CONCLUSION

The study emphasized the complex interaction between the GH and the thyroid axes in patients with GHPA and highlighted the potential effect of glycemic status and tumor volume on thyroid function.

Persistent Orthostatic Hypotension in a Patient With Acromegaly: Resolution With Transsphenoidal Hypophysectomy

Acromegaly is a rare condition characterized by excessive secretion of growth hormone from a pituitary tumor. It can affect multiple systems and can be fatal with cardiac dysfunction being the most common cause of death in these patients. Autonomic dysfunction is a less studied subject in patients with acromegaly, and the exact pathophysiology is still unclear. Here we present a case of a patient with persistent orthostatic hypotension, who was found to have acromegaly and pituitary adenoma upon further evaluation. Her orthostatic symptoms failed to improve with conservative measures and medical management, but unexpectedly resolved after transsphenoidal hypophysectomy was performed.

Electrophysiological features in acromegaly: re-thinking the arrhythmic risk?

BACKGROUND

Acromegaly is disease associated with a specific cardiomyopathy. Hitherto, it has been widely understood that acromegaly carries an increased risk of arrhythmia.

PURPOSE

In this review we show that evidences are limited to a small number of case-control studies that reported increased rates of premature ventricular beats (PVB) but no more significant arrhythmia. In contrast, there are several studies that have reported impaired preclinical markers of arrhythmia, including reduced heart rate variability, increased late potentials, QT interval dispersion, impaired heart rate recovery after physical exercise and left ventricular dysynchrony. Whilst these markers are associated with an adverse cardiovascular prognosis in the general population, they do not have a high independent positive predictive accuracy for arrhythmia. In acromegaly, case reports have described sudden cardiac death, ventricular tachyarrhythmia and advanced atrio-ventricular block that required implantation of a cardio-defibrillator or permanent pacemaker. Treatment with somatostatin analogues can reduce cardiac dysrhythmia in some cases by reducing heart rate, PVBs and QT interval. Pegvisomant reduces mean heart rate. Pasireotide is associated with QT prolongation. In the absence of good quality data on risk of arrhythmia in acromegaly, the majority of position statements and guidelines suggest routine 12-lead electrocardiography (ECG) and transthoracic echocardiography (TTE) in every patient at diagnosis and then follow up dependent on initial findings.

Gastrointestinal symptoms in acromegaly: A case control study

BACKGROUND

Acromegaly is a chronic disease caused by a pituitary somatotroph adenoma resulting in excess secretion of growth hormone, which leads to excess secretion of Insulin like growth factor 1 from the liver, causing abnormal soft tissue growth. There is increasing awareness that diseases affecting connective tissue are associated with an increase in functional gastrointestinal symptoms. Data was collected from patients with a confirmed diagnosis of acromegaly to evaluate the intensity, variety and impact of abdominal symptoms in comparison with a control group who were healthy participants recruited from the local fracture clinic.

AIM

To evaluate the frequency type and burden of abdominal symptoms in acromegaly in comparison with a control group.

METHODS

Medical documentation of patients with a diagnosis of acromegaly treated in one tertiary medical centre between 2010 and 2017 has been analysed. Data was collected from patients with confirmed acromegaly, using the Short Form Health Survey (SF36) and Rome IV Diagnostic questionnaire for Functional Gastrointestinal Disorders in Adults (R4DQ) and compared to a sex- and age-matched control group, to assess the burden of abdominal symptoms. Microsoft Excel and IBM SPSS v 25 were used for data analysis.

RESULTS

Fifty patients with acromegaly (24 male and 26 females; age range 23-64 years, mean 43) and 200 controls (96 male and 104 females; age range 18-84, mean 42.4) were recruited. 92% (46 out of 50) of patients with acromegaly reported abdominal symptoms and 78% (39 out of 50) had at least one functional gastrointestinal disorder according to the Rome IV diagnostic criteria, compared to 16% of controls (OR > 1, P < 0.0001). The most commonly reported symptom was constipation (69% acromegaly vs 21% of controls OR > 1, P < 0.0001, 95%CI: 4.4–15.8). 34 out of 50 (68%) respondents met the criteria for functional constipation according to Rome IV. Upper gastrointestinal disorders were also more prevalent in the acromegaly group. There was no statistically significant difference in the prevalence of biliary and anorectal symptoms between the two groups. Patients in acromegaly group scored lower on the mean scores of the eight parameters of SF36 Quality of Life questionnaire (mean scores 60.04 vs 71.23, 95%CI: -13.6829 to -8.6971, OR > 1, P < 0.001) as compared to the control group.

CONCLUSION

Upper and lower functional gastrointestinal tract disorders (defined by Rome IV diagnostic criteria) are significantly more prevalent in patients with acromegaly compared with healthy age and sex matched controls in our study. Functional constipation is the most commonly reported problem. Poorer quality of life may in part be attributable to the increased prevalence of abdominal symptoms.

GHRH-mediated GH release is associated with sympathoactivation and baroreflex resetting: a microneurographic study in healthy humans

Previous research suggested substantial interactions of growth hormone (GH) and sympathetic nervous activity. This cross talk can be presumed both during physiological (e.g., slow-wave sleep) and pathological conditions of GH release. However, microneurographic studies of muscle sympathetic nerve activity (MSNA) and assessment of baroreflex function during acute GH-releasing hormone (GHRH)-mediated GH release were not conducted so far. In a balanced, double-blind crossover design, GHRH or placebo (normal saline) were intravenously administered to 11 healthy male volunteers. MSNA was assessed microneurographically and correlated with blood pressure (BP) and heart rate (HR) at rest before (pre-) and 30-45 (post-I) and 105-120 min (post-II) after respective injections. Additionally, baroreflex function was assessed via graded infusion of vasoactive drugs. GHRH increased GH serum levels as intended. Resting MSNA showed significant net increases of both burst rate and total activity from pre- to post-I and post-II following GHRH injections compared with placebo (ANOVA for treatment and time, burst rate: P = 0.028; total activity: P = 0.045), whereas BP and HR were not altered. ANCOVA revealed that the dependent variable MSNA was not affected by the independent variables mean arterial BP (MAP) or HR (MAP: P = 0.006; HR: P = 0.003). Baroreflex sensitivity at baroreflex challenge was not altered. GHRH-mediated GH release is associated with a significant sympathoactivation at central nervous sites superordinate to the simple baroreflex feedback loop because GH induced a baroreflex resetting without altering baroreflex sensitivity.

Heart rate variability is reduced in acromegaly patients and improved by treatment with somatostatin analogues

BACKGROUND

Cardiovascular complications, including arrhythmias and cardiac sudden death, are the most common causes of enhanced mortality in acromegaly. However, few data are available on cardiac autonomic functions and sympathovagal balance in acromegalic patients.

OBJECTIVE

The aim of this study was to investigate both the time and frequency domain parameters of Heart Rate Variability (HRV), in order to characterize the cardiac autonomic functions in patients affected by acromegaly. This study correlated anthropometric, metabolic, echocardiographic parameters and blood pressure with those relating to HRV, to identify the main factors responsible for the HRV related alterations possibly present. We also aimed to analyze the effects of the treatment with somatostatin analogues (SSAs) on HRV.

MATERIALS AND METHODS

This study enrolled 47 acromegalic patients (23 males, age 49.1 ± 13.5 years) and 37 (13 males) age matched (52.3 ± 13.3 years) healthy subjects. All participants underwent 12-lead 24 h ECG Holter recordings and a HRV analysis of the ECG tracings was performed. The parameters obtained from the time domain analysis of HRV included pNN50, SDNN, SDNN index, SDANN and RMSSD. The power spectral analysis of HRV was obtained by summing powers of the LF (low frequency) and the HF (high frequency) band. Sympathovagal balance was estimated by calculating the LF/HF ratio during 24 h and 15 min of clinostatism. The HRV of 28 acromegalic patients was studied before and after SSAs treatment.

RESULTS

Acromegalic patients showed significantly lower SDNN and SDANN compared to controls. Diabetic and non-diabetic acromegalic patients showed decreased SDNN and SDANN, when compared to healthy subjects. Diabetic acromegalic patients had a lower LF/HF ratio during 24 h when compared to non-diabetic acromegalic patients. Similar results were obtained analyzing patients affected by acromegaly and impaired glucose tolerance. SDNN and SDANN were lowered by hypertension in the acromegalic population, when compared to controls, and hypertensive acromegalic patients also displayed a decreased LF/HF ratio during 24 h when compared to normotensive acromegalic subjects. Patients with ventricular arrhythmias in Lown classes 3-5 showed a decreased SDANN compared to patients in Lown class 0-2. The treatment with SSAs was able to ameliorate all the time domain parameters of HRV, without altering the 24 h LF/HF ratio.

CONCLUSION

Cardiac autonomic functions and sympathovagal balance are altered in patients affected by acromegaly and could be ameliorated by SSAs therapy. HRV analysis allows an estimation of the autonomic sympathovagal balance and may be a useful clinical tool for the cardiac risk stratification in acromegalic patients.

Increased Short-Term Beat-To-Beat Variability of QT Interval in Patients with Acromegaly

Cardiovascular diseases, including ventricular arrhythmias are responsible for increased mortality in patients with acromegaly. Acromegaly may cause repolarization abnormalities such as QT prolongation and impairment of repolarization reserve enhancing liability to arrhythmia. The aim of this study was to determine the short-term beat-to-beat QT variability in patients with acromegaly. Thirty acromegalic patients (23 women and 7 men, mean age±SD: 55.7±10.4 years) were compared with age- and sex-matched volunteers (mean age 51.3±7.6 years). Cardiac repolarization parameters including frequency corrected QT interval, PQ and QRS intervals, duration of terminal part of T waves (Tpeak-Tend) and short-term variability of QT interval were evaluated. All acromegalic patients and controls underwent transthoracic echocardiographic examination. Autonomic function was assessed by means of five standard cardiovascular reflex tests. Comparison of the two groups revealed no significant differences in the conventional ECG parameters of repolarization (QT: 401.1±30.6 ms vs 389.3±16.5 ms, corrected QT interval: 430.1±18.6 ms vs 425.6±17.3 ms, QT dispersion: 38.2±13.2 ms vs 36.6±10.2 ms; acromegaly vs control, respectively). However, short-term beat-to-beat QT variability was significantly increased in acromegalic patients (4.23±1.03 ms vs 3.02±0.80, P<0.0001). There were significant differences between the two groups in the echocardiographic dimensions (left ventricular end diastolic diameter: 52.6±5.4 mm vs 48.0±3.9 mm, left ventricular end systolic diameter: 32.3±5.2 mm vs 29.1±4.4 mm, interventricular septum: 11.1±2.2 mm vs 8.8±0.7 mm, posterior wall of left ventricle: 10.8±1.4 mm vs 8.9±0.7 mm, P<0.05, respectively). Short-term beat-to-beat QT variability was elevated in patients with acromegaly in spite of unchanged conventional parameters of ventricular repolarization. This enhanced temporal QT variability may be an early indicator of increased liability to arrhythmia.

Thyroid diseases in patients with acromegaly

Acromegaly often involves the presence of different pathologies of the thyroid gland. Long-lasting stimulation of the follicular epithelium by growth hormone (GH) and insulin-like growth factor 1 (IGF-1) can cause disorders in thyroid function, an increase in its mass and the development of goitre. Acromegalic patients present most frequently with non-toxic multinodular goitre. Nodules are more prevalent in patients with active acromegaly. It has been suggested that then thyroid size increases and it can be reduced through treatment with somatostatin analogues. The relationship between thyroid volume and the level of IGF-1 and the duration of the disease is unclear. Each acromegalic patient requires a hormonal and imaging evaluation of the thyroid when the diagnosis is made, and an accurate evaluation during further observation and treatment. Although the data concerning the co-occurrence of acromegaly and thyroid cancer still remain controversial, it is particularly important to diagnose the patient early and to rule out thyroid cancer.

Impact of successful treatment of acromegaly on overnight heart rate variability and sleep apnea

BACKGROUND

Successful treatment of acromegaly improves disease-related cardiovascular mortality and morbidity, but its effects on autonomic modulation of the heart rate are unknown.

OBJECTIVES

We documented treatment-induced changes in time-domain heart rate variability, taking into account the confounding effects of obstructive sleep apnea.

PATIENTS AND METHODS

Sixteen consecutive patients (12 males, aged 43 ± 12 y) with newly diagnosed acromegaly underwent overnight (12:00-7:00 am) cardiac Holter recordings coupled with polysomnography. Data were obtained before and 10 ± 6 months after successful treatment of acromegaly.

RESULTS

IGF-1 levels fell from 807 ± 333 to 207 ± 69 μg/L and normalized in all patients. Seven patients (44%) had obstructive sleep apnea (apnea-hypopnea index 33 ± 21/h) at baseline. Treatment had no significant effect on polysomnographic indices. After treatment, increases were noted in the normal-to-normal heart period (NN), SD-NN, the percentage of NN differing from the previous NN by greater than 50 msec, and the root mean square of successive differences in NN (each P < .05). These heart rate variability results were not influenced by the type of treatment, and there was no relationship between changes in NN and changes in the apnea-hypopnea index (P = .58).

CONCLUSION

Early after successful treatment of acromegaly, we observed increased parasympathetic modulation/decreased sympathetic modulation of the nighttime heart rate, an effect that seems unrelated to changes in sleep apnea status. Treatments aimed at normalizing IGF-1 may improve cardiovascular homeostasis through improved cardiac autonomic nervous system modulation.

Assessment of cardiac autonomic functions by heart rate recovery, heart rate variability and QT dynamicity parameters in patients with acromegaly

Cardiovascular complications are the most common causes of morbidity and mortality in acromegaly. However, there is little data regarding cardiac autonomic functions in these patients. Herein, we aimed to investigate several parameters of cardiac autonomic functions in patients with acromegaly compared to healthy subjects. We enrolled 20 newly diagnosed acromegalic patients (55% female, age:45.7 ± 12.6 years) and 32 age- and gender-matched healthy subjects. All participants underwent 24 h Holter recording. Heart rate recovery (HRR) indices were calculated by subtracting 1st, 2nd and 3rd minute heart rates from maximal heart rate. All patients underwent heart rate variability (HRV) and QT dynamicity analysis. Baseline characteristics were similar except diabetes mellitus and hypertension among groups. Mean HRR1 (29.2 ± 12.3 vs 42.6 ± 6.5, p = 0.001), HRR2 (43.5 ± 15.6 vs 61.1 ± 10.8, p = 0.001) and HRR3 (46.4 ± 16.2 vs 65.8 ± 9.8, p = 0.001) values were significantly higher in control group. HRV parameters as, SDNN [standard deviation of all NN intervals] (p = 0.001), SDANN [SD of the 5 min mean RR intervals] (p = 0.001), RMSSD [root square of successive differences in RR interval] (p = 0.001), PNN50 [proportion of differences in successive NN intervals >50 ms] (p = 0.001) and high-frequency [HF] (p = 0.001) were significantly decreased in patients with acromegaly; but low frequency [LF] (p = 0.046) and LF/HF (p = 0.001) were significantly higher in acromegaly patients. QTec (p = 0.009), QTac/RR slope (p = 0.017) and QTec/RR slope (p = 0.01) were significantly higher in patients with acromegaly. Additionally, there were significant negative correlation of disease duration with HRR2, HRR3, SDNN, PNN50, RMSSD, variability index. Our study results suggest that cardiac autonomic functions are impaired in patients with acromegaly. Further large scale studies are needed to exhibit the prognostic significance of impaired autonomic functions in patients with acromegaly.

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.

Cardiovascular dysfunctions and sympathovagal imbalance in hypertension and prehypertension: physiological perspectives

Hypertension (HTN) and prehypertension (pre-HTN) have been identified as independent risk factors for adverse cardiovascular events. Recently, increased psychosocial stress and work stress have contributed to the increased prevalence of HTN and pre-HTN, in addition to the contribution of obesity, diabetes, poor food habits and physical inactivity. Irrespective of the etiology, sympathetic overactivity has been recognized as the main pathophysiologic mechanism in the genesis of HTN and pre-HTN. Sympathovagal imbalance owing to sympathetic overactivity and vagal withdrawal is reported to be the basis of many clinical disorders. However, the role played by vagal withdrawal has been under-reported. In this review, we have analyzed the pathophysiologic involvement of sympathovagal imbalance in the development of HTN and pre-HTN, and the link of sympathovagal imbalance to cardiovascular dysfunctions. We have emphasized that adaptation to a healthier lifestyle will help improve sympathovagal homeostasis and prevent the occurrence of HTN and pre-HTN.

Decreased adrenergic tone in acromegaly: evidence from direct recording of muscle sympathetic nerve activity

OBJECTIVE

Sympathovagal imbalance has been shown in acromegaly by indirect measurements of adrenergic tone. Data regarding direct measurement of sympathetic activity are lacking as yet. Aim of this study was to assess the adrenergic tone through direct recording of muscle sympathetic nerve activity (MSNA) in acromegalic patients.

DESIGN

Fifteen patients (age 26-66 years, eight women) with newly diagnosed active acromegaly without hyperprolactinaemia, pituitary hormone deficiencies, obstructive sleep apnoea and cardiac hypertrophy, and 15 healthy subjects matched for age, sex and body mass index were recruited. After evaluating anthropometric and echocardiographic parameters, anterior pituitary function, glucose and lipid metabolism, and measuring plasma leptin, direct recording of sympathetic outflow via the microneurographic technique was performed.

RESULTS

For similar anthropometric and metabolic parameters in patients and controls, HOMA index was significantly increased in the former (4·2 ± 2·39 vs 1·6 ± 0·19, P < 0·001). Surprisingly, this finding of insulin resistance was accompanied by a marked sympathetic inhibition (MSNA 18·3 ± 8·10 vs 37·3 ± 6·48 bursts/min, P < 0·0001, respectively in patients and controls). A reduction in plasma leptin (1·6 ± 1·04 vs 6·5 ± 2·01 μg/l, P < 0·0001) was also recorded in the patients. MSNA was positively correlated with leptin (P < 0·0001).

CONCLUSIONS

Newly diagnosed acromegalic patients without cardiac hypertrophy display a decreased sympathetic outflow in spite of insulin resistance. This finding might be related to hypoleptinaemia.

Electrophysiological assessment of the autonomic nervous system in male patients with acromegaly

BACKGROUND/AIMS

We aimed to electrophysiologically evaluate the autonomic function in acromegalic patients using sympathetic skin response (SSR) as a reflection of the sympathetic sudomotor activity and RR interval variation (RRIV) as an indicator of the cardiovagal autonomic function.

METHODS

The study group consisted of 18 male acromegalics, and the control group was composed of 18 age- and sex-matched healthy subjects. Participants underwent SSR and RRIV tests. Beginning latencies and amplitudes of the median and tibial SSRs were compared among the groups. The RRIV values recorded at rest and during hyperventilation were compared among the patients and controls.

RESULTS

Latencies of SSRs recorded from the palms (median) and soles (tibial) of acromegalics were significantly longer than in healthy subjects (p = 0.004, p < 0.001). The amplitude of SSR recorded from the sole (tibial) was significantly decreased (p = 0.028). The RRIVs obtained from acromegalics at rest and during hyperventilation were significantly decreased compared with those of controls (p < 0.001). The RRIVs obtained from controls prolonged significantly during hyperventilation (p < 0.001); however, in the acromegaly group, hyperventilation did not cause a significant change in RRIV (p = 0.983).

CONCLUSIONS

The present study suggests that an autonomic dysfunction exists in patients with acromegaly. Dysautonomia in acromegalics may be documented by means of SSR and RRIV.

Centrally administered ghrelin activates cardiac vagal nerve in anesthetized rabbits

Although central ghrelin has cardioprotective effect through inhibiting sympathetic nerve activity, the effects of central ghrelin on cardiac vagal nerve remain unknown. We investigated the effects of centrally administered ghrelin on cardiac autonomic nerve activities using microdialysis technique. A microdialysis probe was implanted in the right atrial wall adjacent to the sinoatrial node of an anesthetized rabbit and was perfused with Ringer's solution containing a cholinesterase inhibitor, eserine. After injection of ghrelin (1 nmol) into the right lateral cerebral ventricle, norepinephrine (NE) and acetylcholine (ACh) concentrations in the dialysate samples were measured as indices of NE and ACh release from nerve endings to the sinoatrial node using high-performance liquid chromatography. Heart rate was 270±4 bpm at baseline and decreased gradually after ghrelin injection to 234±9 bpm (P<0.01) at 60-80 min, followed by gradual recovery. Dialysate ACh concentration was 5.5±0.8 nM at baseline and increased gradually after ghrelin injection to 8.8±1.2 nM (P<0.01) at 60-80 min; the concentration started to decrease gradually from 100 to 120 min after injection reaching 5.6±0.8 nM at 160-180 min. Central ghrelin did not change mean arterial pressure or dialysate NE concentration. The elevated dialysate ACh concentration declined rapidly after transection of cervical vagal nerves. These results indicate that centrally administered ghrelin activates cardiac vagal nerve.

Pathogenesis of adolescent idiopathic scoliosis in girls - a double neuro-osseous theory involving disharmony between two nervous systems, somatic and autonomic expressed in the spine and trunk: possible dependency on sympathetic nervous system and hormones with implications for medical therapy

Anthropometric data from three groups of adolescent girls - preoperative adolescent idiopathic scoliosis (AIS), screened for scoliosis and normals were analysed by comparing skeletal data between higher and lower body mass index subsets. Unexpected findings for each of skeletal maturation, asymmetries and overgrowth are not explained by prevailing theories of AIS pathogenesis. A speculative pathogenetic theory for girls is formulated after surveying evidence including: (1) the thoracospinal concept for right thoracic AIS in girls; (2) the new neuroskeletal biology relating the sympathetic nervous system to bone formation/resorption and bone growth; (3) white adipose tissue storing triglycerides and the adiposity hormone leptin which functions as satiety hormone and sentinel of energy balance to the hypothalamus for long-term adiposity; and (4) central leptin resistance in obesity and possibly in healthy females. The new theory states that AIS in girls results from developmental disharmony expressed in spine and trunk between autonomic and somatic nervous systems. The autonomic component of this double neuro-osseous theory for AIS pathogenesis in girls involves selectively increased sensitivity of the hypothalamus to circulating leptin (genetically-determined up-regulation possibly involving inhibitory or sensitizing intracellular molecules, such as SOC3, PTP-1B and SH2B1 respectively), with asymmetry as an adverse response (hormesis); this asymmetry is routed bilaterally via the sympathetic nervous system to the growing axial skeleton where it may initiate the scoliosis deformity (leptin-hypothalamic-sympathetic nervous system concept = LHS concept). In some younger preoperative AIS girls, the hypothalamic up-regulation to circulating leptin also involves the somatotropic (growth hormone/IGF) axis which exaggerates the sympathetically-induced asymmetric skeletal effects and contributes to curve progression, a concept with therapeutic implications. In the somatic nervous system, dysfunction of a postural mechanism involving the CNS body schema fails to control, or may induce, the spinal deformity of AIS in girls (escalator concept). Biomechanical factors affecting ribs and/or vertebrae and spinal cord during growth may localize AIS to the thoracic spine and contribute to sagittal spinal shape alterations. The developmental disharmony in spine and trunk is compounded by any osteopenia, biomechanical spinal growth modulation, disc degeneration and platelet calmodulin dysfunction. Methods for testing the theory are outlined. Implications are discussed for neuroendocrine dysfunctions, osteopontin, sympathoactivation, medical therapy, Rett and Prader-Willi syndromes, infantile idiopathic scoliosis, and human evolution. AIS pathogenesis in girls is predicated on two putative normal mechanisms involved in trunk growth, each acquired in evolution and unique to humans.

Diminished and irregular thyrotropin secretion with preserved diurnal rhythm in patients with active acromegaly

CONTEXT

The hypothalamo-pituitary-thyroid axis in acromegaly may be altered. Previous studies report diminished serum TSH concentrations in patients with active acromegaly and decreased response to TRH. On the other hand, most patients have normal thyroid hormone concentrations.

OBJECTIVE

Our aim was to analyze serum TSH profiles in relation to GH profiles in patients with untreated acromegaly, in order to delineate aberrations in the hypothalamo-pituitary-thyroid system.

INTERVENTION

Twenty-one patients with active acromegaly and matched controls underwent a 24-h, 10-min blood sampling study. GH and TSH data were analyzed with a newly developed automated deconvolution program, approximate entropy, and cosinor regression.

RESULTS

Basal (10.4 +/- 2.0 vs. 13.8 +/- 1.4 mU/liter . 24 h; P = 0.02) and pulsatile (11.4 +/- 1.7 vs. 18.6 +/- 1.6 mU/liter . 24 h; P = 0.002) TSH secretion was decreased in patients. TSH secretory regularity was diminished with loss of pattern synchrony between TSH and GH. Total TSH secretion correlated with TSH increase after TRH (R = 0.75; P = 0.0001), negatively with the log-transformed GH secretion rate (R = -0.52; P = 0.001), but not with adenoma size. The diurnal TSH rhythm was preserved. Total and free T4 concentrations were similar in patients and controls.

CONCLUSION

Basal and pulsatile TSH secretion is decreased in active acromegaly, although T4 levels are unaffected. Diminished TSH secretion is compatible with enhanced restraint by tumoral GH feedback-driven somatostatin outflow, explaining also the reduced regularity of TSH secretion. Unchanged T4 concentrations might reflect decreased sympathetic function in GH excess states, heightening responsiveness of the thyroid gland to TSH.

Cardiovascular autonomic function in Cushing's syndrome

Cardiac autonomic dysfunction is associated with increased cardiovascular mortality. No data on sympathovagal balance are available in patients with Cushing's syndrome, in whom cardiovascular risk is high. We studied 10 patients with newly diagnosed Cushing's syndrome (1 male/9 females; age mean+/-SD, 47+/-10 yr) and 10 control subjects matched for age, sex, body mass index, and cardiovascular risk factors. In both groups there were 7 patients with arterial hypertension, 3 with diabetes mellitus, and 2 with obesity. Cardiac autonomic function was evaluated by analysis of short time heart rate variability (HRV) measures in frequency domain over 24-h, daytime, and nighttime. The 24-h ambulatory blood pressure monitoring and echocardiography were also performed. In comparison with controls, patients with Cushing's syndrome had lower 24-h (1.3+/-0.6 vs 3.7+/-1.5, mean+/-SD, p<0.01), daytime (2.0+/-1.4 vs 4.5+/-1.6, p<0.01), and night-time (1.0+/-0.4 vs 3.5+/-2.3, p<0.01) low-frequency/ high frequency (LF/HF) power ratio. In the presence of similar LF power, the difference was due to elevation in HF power in Cushing's syndrome compared to controls: 24-h, 12.7+/-6.7 vs 5.8+/-2.8, p<0.01; daytime, 10.2+/-7.3 vs 4.5+/-2.1, p<0.05; nighttime, 14.2+/-7.0 vs 7.8+/-4.7, p<0.05. Eight Cushing patients vs 4 controls had a non-dipping blood pressure profile. At echocardiography, Cushing patients had a greater left ventricular mass index and/or relative wall thickness, and impaired diastolic function, compared with controls. Compared to controls, patients with Cushing's syndrome showed a sympathovagal imbalance, characterized by a relatively increased parasympathetic activity. Whether this autonomic alteration is meant to counterbalance cortisol-induced effects on blood pressure and cardiac structure/function or has a different pathophysiological significance is still unknown.

Sympathovagal imbalance in transsexual subjects

CONTEXT

Autonomic nervous system imbalance is related to cardiovascular risk. Heart rate variability (HRV) indexes are associated with age, race, and sex, but the role of sex hormones is still unknown.

OBJECTIVE

To evaluate sympathovagal balance (SB) in transsexuals.

PATIENTS

Eighteen transsexual subjects, 12 male-to-female (group 1) and 6 female- to-male (group 2), compared with 34 age-matched controls: 17 males (group 3) and 17 females (group 4). Autonomic testing of SB was performed by Power Spectral Analysis (PSA) of HRV in clinostatism (c) and orthostatism (o). PSA identifies power peaks: high frequency (HF) expresses vagal activity, while low frequency (LF) expresses sympathetic activity.

RESULTS

Group 1 showed lower LFc than groups 2, 3, and 4 (p<0.001, p=0.05, p<0.001, respectively), and lower LFo than groups 3 and 4 (p=0.01); HFc was lower than in groups 2, 3, and 4 (p=0.02, p=0.02, p<0.001, respectively), and HFo was lower than in groups 3 and 4 (p<0.001). LFo/HFo ratio was higher in group 1 than in group 4 (p<0.001). No differences emerged between groups 2 and 3. Group 2 showed lower HFo than group 4 (p=0.03), and a higher LFo/HFo ratio (p=0.01). Group 3 showed lower HFo and HFc than group 4 (p=0.02, p=0.05, respectively), and a higher LFo/HFo ratio (p=0.03).

CONCLUSION

In this study we found a sympathovagal imbalance due to a reduced sympathetic and parasympathetic influence on heart rate. Sex hormone therapy per se may play a role in this imbalance, and HRV measurement could be useful in detecting cardiovascular risk in transsexuals.

Evidence of prolonged orocecal transit time and small intestinal bacterial overgrowth in acromegalic patients

CONTEXT

Gastrointestinal abnormalities in acromegaly include dolichomegacolon, slow colonic transit, and increased prevalence of colonic polyps. Conversely, no data are available on the small intestine.

OBJECTIVE

The aim of the study was to investigate the orocecal transit time (OCTT) and the presence of small intestinal bacterial overgrowth (SIBO).

PATIENTS

A total of 41 acromegalic patients and 30 sex- and age-matched control subjects entered the study. Acromegalic patients were classified according to the medical treatment with somatostatin analogs as "treated" (n = 22) and "untreated" (n = 19), whereas according to the disease control, as "controlled" (n = 17), "uncontrolled" (n = 10), and "partially controlled" (n = 14). Patients and controls completed a questionnaire and underwent a standardized 10-g lactulose hydrogen breath test to determine the OCTT and presence of SIBO. SIBO-positive patients underwent eradication with rifaximine.

RESULTS

An increased prevalence of SIBO (18 of 41 vs. 1 of 30; P < 0.0001) and a significantly delayed OCTT (169.53 +/- 8.15 vs. 107.25 +/- 6.56 min; P < 0.0001) were evidenced in patients compared with controls. No significant statistical differences were found between "treated" or "untreated" patients positive for SIBO or between "controlled," "partially controlled," and "uncontrolled" patients. OCTT was significantly delayed in "treated" vs. "untreated" patients (183.21 +/- 9.01 and 158.89 +/- 6.38, respectively; P = 0.02) and in patients compared with controls (105.75 +/- 6.34; P < 0.0001). Rifaximine eradicated SIBO in more than 50% of patients who underwent treatment.

CONCLUSIONS

These data demonstrate for the first time that SIBO occurs more frequently in acromegalic patients, however, it can be successfully treated by a specific antibiotic. Medical therapy with somatostatin analogs does not affect SIBO prevalence. OCTT resulted significantly prolonged in both "treated" and "untreated" patients, suggesting that acromegaly determines per se an impairment of the intestinal motility. Indeed, disease control seems irrelevant on the delayed OCTT, suggesting that this alteration might be an irreversible complication of acromegaly, probably related to an autonomic intestinal disorder, as we have previously demonstrated at the cardiac level.

Impact of somatostatin analogs on the heart in acromegaly: a metaanalysis

CONTEXT

Acromegaly can be complicated by cardiomyopathy. Treatment with somatostatin analogs has been shown to improve some cardiac parameters, but most published clinical trials involved few patients and were not randomized or controlled. In addition, their results are rather variable.

OBJECTIVE

The objective of the study was to conduct a metaanalysis aimed at obtaining a more accurate picture of the effect of somatostatin analogs on the heart in patients with acromegaly.

DESIGN

We systematically reviewed all studies of somatostatin analogs in acromegaly. Eighteen studies were identified in three databases. We conducted a combined analysis of the effects of somatostatin analogs by using the overall effect size to evaluate significance and by computing the weighted mean differences with and without treatment to assess the effect size.

RESULTS

Somatostatin analog treatment was associated with significant reductions in the heart rate [-5.8 (2.1) beats/min], the left ventricular mass index [-22.3 (6.7) g/m(2)], interventricular septum thickness [-0.3 (0.2) mm], left ventricular posterior wall thickness [-0.8 (0.4) mm], and the ratio of the E-wave and A-wave peak velocities of the mitral flow profile [0.2 (0.1)]. It was also associated with improved exercise tolerance [1.6 (0.4) min]. Trends toward beneficial effects were noted for the left ventricular end-diastolic dimension [-1.5 (2.2) mm] and the left ventricular ejection fraction [3.3% (1.7%)]. Overall effect sizes were not significant for blood pressure, left ventricular end-systolic dimension, or fractional shortening. Bigger improvements were observed in studies with larger falls in IGF-I and/or GH levels and studies of younger patients.

CONCLUSION

This metaanalysis confirms that somatostatin analog therapy aimed at achieving stringent control of serum GH/IGF-I concentrations in patients with acromegaly is associated with significant positive effects on morphological and functional hemodynamic parameters.