Ventilation threshold as a measure of impaired physical performance in adults with growth hormone excess

Body Composition, Sarcopenia, and Serum Myokines in Acromegaly: A Narrative Review

Patients with active acromegaly have a higher percentage of lean body mass, a lower percentage of fat body mass, and an increase in their extracellular water compartment compared to healthy individuals. However, muscle function appears to be compromised in patients with acromegaly, with some experiencing worsened physical performance and sarcopenia. Myokine alterations, insulin resistance, dysregulation of protein metabolism, muscle oxidative stress, neuromuscular junction impairment, and increased ectopic intramuscular fat deposits may play roles in muscle dysfunction in patients with acromegaly.

Aerobic exercise interventions to address impaired quality of life in patients with pituitary tumors

Patients with pituitary tumors may experience persistent fatigue and reduced physical activity, based on subjective measures after treatment. These symptoms may persist despite gross total resection of their tumors and biochemical normalization of pituitary function. While reduced quality of life has been commonly acknowledged in pituitary tumor patients, there is a lack of studies on what interventions may be best implemented to ameliorate these issues, particularly when hormonal levels have otherwise normalized. Aerobic exercise programs have been previously described to ameliorate symptoms of chronic fatigue and reduced physical capacity across a variety of pathologies in the literature. As such, a prescribed aerobic exercise program may be an underrecognized but potentially impactful intervention to address quality of life in pituitary tumor patients. This review seeks to summarize the existing literature on aerobic exercise interventions in patients with pituitary tumors. In addition, future areas of study are discussed, including tailoring exercise programs to the hormonal status of the patient and incorporating more objective measures in monitoring response to interventions.

Playing around the anaerobic threshold during COVID-19 pandemic: advantages and disadvantages of adding bouts of anaerobic work to aerobic activity in physical treatment of individuals with obesity

INTRODUCTION

Obesity is a condition that generally limits work capacity and predisposes to a number of comorbidities and related diseases, the last being COVID-19 and its complications and sequelae. Physical exercise, together with diet, is a milestone in its management and rehabilitation, although there is still a debate on intensity and duration of training. Anaerobic threshold (AT) is a broad term often used either as ventilatory threshold or as lactate threshold, respectively, detected by respiratory ventilation and/or respiratory gases (VCO₂ and VO₂), and by blood lactic acid.

AIMS AND METHODOLOGY

This review outlines the role of AT and of the different variations of growth hormone and catecholamine, in subjects with obesity vs normal weight individuals below and beyond AT, during a progressive increase in exercise training. We present a re-evaluation of the effects of physical activity on body mass and metabolism of individuals with obesity in light of potential benefits and pitfalls during COVID-19 pandemic. Comparison of a training program at moderate-intensity exercise (< AT) with training performed at moderate intensity (< AT) plus a final bout of high-intensity (> AT) exercise at the end of the aerobic session will be discussed.

RESULTS

Based on our data and considerations, a tailored strategy for individuals with obesity concerning the most appropriate intensity of training in the context of rehabilitation is proposed, with special regard to potential benefits of work program above AT.

CONCLUSION

Adding bouts of exercise above AT may improve lactic acid and H⁺ disposal and improve growth hormone. Long-term aerobic exercise may improve leptin reduction. In this way, the propensity of subjects with obesity to encounter a serious prognosis of COVID-19 may be counteracted and the systemic and cardiorespiratory sequelae that may ensue after COVID-19, can be overcome. Individuals with serious comorbidities associated with obesity should avoid excessive exercise intensity.

Updates in rare and not-so-rare complications of acromegaly: focus on respiratory function and quality of life in acromegaly

Acromegaly is a complex disease with excessive growth hormone and insulin-like growth factor 1 (IGF-1) causing multisystem effects, particularly cardiovascular, respiratory, and metabolic. Psychological concerns and poor quality of life (QoL) are also major disease consequences. This review is intended for clinicians and focuses on the latest developments related to respiratory and QoL effects of long-term growth hormone excess. Along with biochemical disease control, patient treatment satisfaction and outcomes have become major treatment objectives; current knowledge and tools to evaluate and manage this aspect of the disease are described. Sleep apnea syndrome and other derangements of lung function and apparatus, from pathophysiology to treatment, and evaluation tools and determinants of QoL in patients with acromegaly are discussed.

Physical exercise improves functional capacity and quality of life in patients with acromegaly: a 12-week follow-up study

OBJECTIVE

Although the focus of acromegaly treatment is the hormonal control of the disease, a new perspective must be given to the functional rehabilitation of these patients, especially when considering the recent increase in survival. The aim of this study was to evaluate the effects of therapist-oriented home rehabilitation (TOHR) on patients with acromegaly.

PATIENTS AND METHODS

Seventeen adults with acromegaly followed an exercise programme from a booklet with instructions for each exercise prescribed, for 2 months, and were reassessed after 1 month of washout. At each of the 3 timepoints (before and after the intervention and at the 1-month follow-up), the participants were subjected to the following assessments: body composition through bioimpedance, health-related quality of life (HRQoL) using the Acromegaly Quality of Life (AcroQoL) questionnaire, general fatigue through the Functional Assessment of Chronic Illness Therapy-Fatigue scale, handgrip strength, lower extremity functionality using isometric dynamometry and the Lower Extremity Functional Scale (LEFS), body balance through stabilometry, and functional capacity through 6-minute walking distance (6MWD).

RESULTS

After performing TOHR, improvements in general fatigue, quadriceps muscle strength, LEFS, 6MWD, balance control and all AcroQoL dimensions were observed (all P < 0.05). After 1 month of washout, however, these gains were lost for all parameters, except the LEFS and balance control.

CONCLUSIONS

In acromegaly, TOHR results in improvements in muscle function, functional capacity, general fatigue, body balance, and HRQoL. Large randomized controlled trials are needed to replicate these benefits and to recommend rehabilitation, especially for those with long-term illness.

Clinical and functional variables can predict general fatigue in patients with acromegaly: an explanatory model approach

OBJECTIVE

To evaluate whether hormonal profile, arterial function, and physical capacity are predictors of fatigue in patients with acromegaly. Subjects and methods: This is a cross-sectional study including 23 patients. The subjects underwent a Modified Fatigue Impact Scale (MFIS) assessment; serum growth hormones (GH) and IGF-1 measurements; pulse wave analysis comprising pulse wave velocity (PWV), arterial compliance (AC), and the reflection index (IR1,2); dominant upper limb dynamometry (DYN); and the six-minute walking distance test (6MWT). Multiple linear regression models were used to identify predictors for MFIS. The coefficient of determination R2 was used to assess the quality of the models' fit. The best model was further analyzed using a calibration plot and a limits of agreement (LOA) plot.

RESULTS

The mean ± SD values for the participants' age, MFIS, PWV, AC, IR1,2, DYN, and the distance in the 6MWT were 49.4 ± 11.2 years, 31.2 ± 18.9 score, 10.19 ± 2.34 m/s, 1.08 ± 0.46 x106 cm5/din, 85.3 ± 29.7%, 33.9 ± 9.3 kgf, and 603.0 ± 106.1 m, respectively. The best predictive model (R2 = 0.378, R2 adjusted = 0.280, standard error = 16.1, and P = 0.026) comprised the following regression equation: MFIS = 48.85 - (7.913 × IGF-I) + (1.483 × AC) - (23.281 × DYN).

CONCLUSION

Hormonal, vascular, and functional variables can predict general fatigue in patients with acromegaly.

Systemic Complications of Acromegaly and the Impact of the Current Treatment Landscape: An Update

Acromegaly is a chronic systemic disease with many complications and is associated with increased mortality when not adequately treated. Substantial advances in acromegaly treatment, as well as in the treatment of many of its complications, mainly diabetes mellitus, heart failure, and arterial hypertension, were achieved in the last decades. These developments allowed change in both prevalence and severity of some acromegaly complications and furthermore resulted in a reduction of mortality. Currently, mortality seems to be similar to the general population in adequately treated patients with acromegaly. In this review, we update the knowledge in complications of acromegaly and detail the effects of different acromegaly treatment options on these complications. Incidence of mortality, its correlation with GH (cumulative exposure vs last value), and IGF-I levels and the shift in the main cause of mortality in patients with acromegaly are also addressed.

Complications of acromegaly: cardiovascular, respiratory and metabolic comorbidities

Acromegaly is associated with an enhanced mortality, with cardiovascular and respiratory complications representing not only the most frequent comorbidities but also two of the main causes of deaths, whereas a minor role is played by metabolic complications, and particularly diabetes mellitus. The most prevalent cardiovascular complications of acromegaly include a cardiomyopathy, characterized by cardiac hypertrophy and diastolic and systolic dysfunction together with arterial hypertension, cardiac rhythm disorders and valve diseases, as well as vascular endothelial dysfunction. Biochemical control of acromegaly significantly improves cardiovascular disease, albeit completely recovering to normal mainly in young patients with short disease duration. Respiratory complications, represented mainly by sleep-breathing disorders, particularly sleep apnea, and respiratory insufficiency, frequently occur at the early stage of the disease and, although their severity decreases with disease control, this improvement does not often change the indication for a specific therapy directed to improve respiratory function. Metabolic complications, including glucose and lipid disorders, are variably reported in acromegaly. Treatments of acromegaly may influence glucose metabolism, and the presence of diabetes mellitus in acromegaly may affect the choice of treatments, so that glucose homeostasis is worth being monitored during the entire course of the disease. Early diagnosis and prompt treatment of acromegaly, aimed at obtaining a strict control of hormone excess, are the best strategy to limit the development or reverse the complications and prevent the premature mortality.

Comparison of low-normal and high-normal IGF-1 target levels during growth hormone replacement therapy: A randomized clinical trial in adult growth hormone deficiency

BACKGROUND

Current guidelines state that the goals of growth hormone (GH) therapy in adults should be an appropriate clinical response, avoidance of side effects, and an IGF-1 value within the age-adjusted reference range. There are no published studies on the target level for IGF-1 that offer specific guidance in this regard.

OBJECTIVES

To compare low-normal and high-normal target levels of IGF-1 on efficacy and safety of GH treatment.

METHODS

A randomized, open-label, clinical trial including thirty-two adults from one university hospital receiving GH therapy for at least one year with a stable IGF-1 concentration between -1 and 1 SD score (SDS). Subjects were randomized to receive either a decrease (IGF-1 target level of -2 to -1 SDS) or an increase of their daily GH dose (IGF-1 target level of 1 to 2 SDS) for a period of 24weeks. The effect on cardiovascular risk factors and physical performance, next to tolerability, was compared.

RESULTS

Thirty subjects (65.6% men, mean age 46.6 (SD 9.9) years) could be analyzed. In subjects with a high-normal IGF-1 target level, waist circumference decreased (p=0.05), and overall they felt better (p=0.04), compared to subjects with a low-normal IGF-1 target level. However, increasing IGF-1 levels led to more myalgia, and decreasing IGF-1 levels to more fatigue. There was a gender-dependent difference in effect on HDL cholesterol.

CONCLUSION

Although increasing GH dose to IGF-1 levels between 1 and 2 SDS improved waist circumference and well-being, safety was not guaranteed with the demonstrated effect on HDL cholesterol in men, and reported myalgia.

Physical and cardiovascular performance in cases with acromegaly after regular short-term exercise

OBJECTIVE

Impaired physical performance is a disturbing complication of acromegaly. We aimed to evaluate the role of regular exercise in amelioration of the impaired physical performance in acromegaly.

METHODS

Patients with acromegaly were divided into two groups according to their participation in a prescheduled programme of exercise. Participants in the study group were exercised 3 days a week for 3 consecutive months. Exercise tolerance was evaluated by maximal oxygen consumption (VO2 max) and time (T) taken to complete the Bruce protocol, muscle flexibility by the sit and reach test (SRT) and muscle strength by the hand grip strength test (HGST). Concomitantly, anthropometric assessment was performed using body mass index (BMI), waist-to-hip ratio (WHR), skinfold measurements from 8 points, percentage body fat (PBF), fat mass (FM) and lean body mass (LBM).

RESULTS

After 3 months of exercise, VO2 max and T were higher in cases that exercised than in cases that did not (P = 0.004 and P = 0.001). Over 3 months, within the exercise group, VO2 max and T of the Bruce protocol increased (P = 0.003 and P = 0.004) and heart rate during warming decreased (P = 0.04). SRT increased within the exercise group after 3 months (P = 0.004). HGSRT did not change significantly (right P = 0.06 and left P = 0.2). The sum of skinfolds, BMI, WHR and LBM remained stable over the study period (P = 0.1, P = 0.08, P = 0.3 and P = 0.09). PBF decreased slightly and FM decreased significantly over 3 months (P = 0.05 and P = 0.03).

CONCLUSION

Even short-term exercise may improve impaired physical performance, muscle activity and disturbed body fat composition in acromegaly.

What is the effect of peripheral muscle fatigue, pulmonary function, and body composition on functional exercise capacity in acromegalic patients?

[Purpose] The six-minute walk test (6MWT) is increasingly being used as an important tool for analyzing functional capacity in patients with multisystem disorders. The aim of this study was to evaluate the effect of body composition, peripheral muscle function, and pulmonary function on the six-minute walk distance (6MWD) in acromegalic patients. [Subjects and Methods] Thirty-two patients with active acromegaly, with a mean age of 48.6 ± 12.1 years, underwent an evaluation of body composition using electrical bioimpedance, isometric dynamometry with surface electromyography, tests of pulmonary function, and the 6MWT. [Results] The mean ± SD values for the 6MWD, fat-free mass (FFM), and maximal expiratory pressure (MEP) were 65.5 ± 11.7% predicted, 55.1 ± 10.6 kg, and 55.2 ± 16.8% predicted, respectively. There was a significant correlation between the 6MWD and the following parameters: the angle of the linear regression line obtained using the values of the median frequency electromyography signal over time during the fatigability test for the vastus medialis muscle (MDF, r=0.65), FFM (r=0.62), MEP (r=0.60), height⁽²⁾/resistance index (r=0.52), resistance (r=−0.50), and forced expiratory volume in 1 second (r=0.50). Multivariate analysis showed that MDF, FFM, and MEP were independent predictors of the 6MWD (R²=0.52). [Conclusion] The fatigability of the peripheral muscles, FFM, and MEP are the primary determinants of the 6MWD in acromegalics.

Growth hormone administration: is it safe and effective for athletic performance

Human growth hormone (GH) is widely abused by athletes; however, there is little evidence that GH improves physical performance. Replacement of GH in GH deficiency improves some aspects of exercise capacity. There is evidence for a protein anabolic effect of GH in healthy adults and for increased lean body mass following GH, although fluid retention likely contributes to this increase. The evidence suggests that muscle strength, power, and aerobic exercise capacity are not enhanced by GH administration, however GH may improve anaerobic exercise capacity. There are risks of adverse effects of long-term abuse of GH. Sustained abuse of GH may lead to a state mimicking acromegaly, a condition with increased morbidity and mortality.

The physiology of growth hormone and sport

The growth hormone (GH)/ insulin-like growth factor-I (IGF-I) axis exerts short-and long-term metabolic effects that are potentially important during exercise. Exercise is a potent stimulus to GH release and there is some evidence that the acute increase in GH is important in regulating substrate metabolism post-exercise. Regular exercise also increases 24-hour GH secretion rates, which potentially contributes to the physiologic changes induced by training. The effects of GH replacement in GH-deficient adults provide a useful model with which to study the effects of the more long-term effects of the GH/ IGF-I axis. There is convincing evidence that GH replacement increases exercise capacity. Measures of exercise performance including maximal oxygen uptake (VO2max) and ventilatory threshold (VeT) are impaired in GH deficiency and improved by GH replacement, probably through some combination of increased oxygen delivery to exercising muscle, increased fatty acid availability with glycogen sparing, increased muscle strength, improved body composition and improved thermoregulation. Administration of supraphysiologic doses of GH to athletes increases fatty acid availability and reduces oxidative protein loss particularly during exercise, and increases lean body mass. It is not known whether these effects translate to improved athletic performance, although recombinant human GH is known to be widely abused in sport. The model of acromegaly provides evidence that long-term GH excess does not result in improved performance but it is possible that a "window" exists in which the protein anabolic effects of supraphysiologic GH might be advantageous.

Medical consequences of acromegaly: what are the effects of biochemical control?

This chapter discusses the effects of biochemical control of acromegaly on cardiovascular diseases, metabolic complications, respiratory abnormalities, malignancies and bone alterations. Acromegaly is associated with increased morbidity and mortality for cardiovascular and respiratory complications, whereas neoplasms seem to be a minor cause of increased risk of death. Other associated diseases are osteoarthritis, carpal tunnel syndrome, fatigue, visual abnormalities and reproductive disorders. Acromegaly results in premature death because of prolonged elevation of GH an IGF-I levels, and a strong biochemical control improves well-being and restores life expectancy to normal. The main goals of medical treatment of acromegaly include normalization of biochemical markers of disease activity, improvement in signs and symptoms of the disease, removal or reduction of tumor mass and preservation of pituitary function.

The growth hormone/insulin-like growth factor-I axis in exercise and sport

The syndrome of adult GH deficiency and the effects of GH replacement therapy provide a useful model with which to study the effects of the GH/IGF-I axis on exercise physiology. Measures of exercise performance including maximal oxygen uptake and ventilatory threshold are impaired in adult GH deficiency and improved by GH replacement, probably through some combination of increased oxygen delivery to exercising muscle, increased fatty acid availability with glycogen sparing, increased muscle strength, improved body composition, and improved thermoregulation. In normal subjects, in addition to the long-term effects of GH/IGF-I status, there is evidence that the acute GH response to exercise is important in regulating substrate metabolism after exercise. Administration of supraphysiological doses of GH to athletes increases fatty acid availability and reduces oxidative protein loss, particularly during exercise, and increases lean body mass. Despite a lack of evidence that these metabolic effects translate to improved performance, GH abuse by athletes is widespread. Tests to detect GH abuse have been developed based on measurement in serum of 1) indirect markers of GH action, and 2) the relative proportions of the two major naturally occurring isoforms (20 and 22kDa) of GH. There is evidence that exercise performance and strength are improved by administration of GH and testosterone in combination to elderly subjects. The potential benefits of GH in these situations must be weighed against potential adverse effects.

The influence of growth hormone status on physical impairments, functional limitations, and health-related quality of life in adults

The availability of recombinant human GH and somatostatin analogs has resulted in widespread treatment for adults with GH deficiency (GHD) and those with GH excess (acromegaly). Despite being at opposite ends of the spectrum in terms of their GH/IGF-I axis, both of these populations experience overlapping somatic impairments. Adults with untreated GHD have low circulating levels of IGF-I that manifest as altered body composition with increased fat and reduced lean body and skeletal muscle mass. At the other end of the spectrum, adults with GH excess, who have elevated levels of IGF-I, also have altered body composition. Impairments that result from disorders of either GHD or GH excess are both associated with increased functional limitations, such as reduced ability to walk quickly for prolonged periods, and poorer health-related quality of life (HR-QoL). Adults with untreated GHD and GH excess both commonly complain of excessive fatigue that seems to be associated more with impaired aerobic than muscular performance. Several studies have documented that administration of GH or somatostatin analogs to adults with GHD or GH excess, respectively, ameliorates abnormal biochemical profile and the associated somatic impairments. However, whether these improvements translate into improved physical function in adults with GHD or GH excess remains largely unknown, and their impact on HR-QoL controversial. Review of placebo-controlled trials to date suggests that GH and somatostatin analogs have greater effects on gas exchange and aerobic performance than as anabolic agents on skeletal muscle mass and function. Future investigations should include dose-response studies to establish the optimal combination of pharmacological agents plus exercise required to improve not only biochemical markers but also physical function and HR-QoL in adults with GHD or GH excess.

Anabolic growth hormone action improves submaximal measures of physical performance in patients with HIV-associated wasting

Growth hormone (GH) treatment reverses the muscle loss allegedly responsible for diminished aerobic capacity and increased fatigue in patients with HIV-associated wasting. This study examined whether submaximal measures of physical performance can be used as objective measures of the functional impact of GH treatment-induced anabolism. We randomized 27 HIV-positive men [mean (SD) age, 43.9 (7.2) yr; body mass, 71.9 (10.4) kg; BMI, 23.1 (2.8) kg/m2] with unintentional weight loss despite antiretroviral therapy to receive GH (6 mg) or placebo in a double-blinded, placebo-controlled, cross-over trial with a 3-mo washout. Lean body mass (LBM), maximum oxygen uptake (Vo2 peak), ventilatory threshold (VeT), 6-min walk test (6MWT) distance and work, profile of mood states (POMS) fatigue and vigor scores, and Nottingham health profile (NHP) energy and physical mobility scores were measured. LBM significantly increased after 3 mo of GH treatment vs. placebo (means +/- SE, 3.7 +/- 0.6 vs. 0.3 +/- 0.4 kg; P < 0.001). VeT significantly improved (17.6 +/- 3.7 vs. -5.9 +/- 2.5%; P < 0.001), but Vo2 peak did not change significantly. 6MWT distance improved (24.9 +/- 9.7 vs. 19.9 +/- 11.6 m; P > 0.05) and 6MWT work increased significantly more after 3 mo of GH treatment (33.3 +/- 8.8 vs. 16.5 +/- 7.5 kJ; P < 0.05). POMS scores of fatigue and vigor and the NHP score of energy improved, yet the changes were not statistically significant. GH treatment improved VeT linearly to the increase in LBM (r =0.43, P = 0.037) and 6MWT work (r = 0.51, P = 0.008), and the increase in 6MWT work correlated with increase in LBM (r = 0.45, P = 0.024). Improvement in 6MWT work above the median (27.3 kJ) showed a decrease in fatigue (r = -0.62, P = 0.024). We concluded that GH treatment-induced LBM gains in HIV-associated wasting were functionally relevant, as determined by effort-independent submaximal measures of cardiopulmonary exercise testing.

Systemic complications of acromegaly: epidemiology, pathogenesis, and management

This review focuses on the systemic complications of acromegaly. Mortality in this disease is increased mostly because of cardiovascular and respiratory diseases, although currently neoplastic complications have been questioned as a relevant cause of increased risk of death. Biventricular hypertrophy, occurring independently of hypertension and metabolic complications, is the most frequent cardiac complication. Diastolic and systolic dysfunction develops along with disease duration; and other cardiac disorders, such as arrhythmias, valve disease, hypertension, atherosclerosis, and endothelial dysfunction, are also common in acromegaly. Control of acromegaly by surgery or pharmacotherapy, especially somatostatin analogs, improves cardiovascular morbidity. Respiratory disorders, sleep apnea, and ventilatory dysfunction are also important contributors in increasing mortality and are advantageously benefitted by controlling GH and IGF-I hypersecretion. An increased risk of colonic polyps, which more frequently recur in patients not controlled after treatment, has been reported by several independent investigations, although malignancies in other organs have also been described, but less convincingly than at the gastrointestinal level. Finally, the most important cause of morbidity and functional disability of the disease is arthropathy, which can be reversed at an initial stage, but not if the disease is left untreated for several years.

Myostatin is a skeletal muscle target of growth hormone anabolic action

Myostatin is a cytokine that has recently been shown to selectively and potently inhibit myogenesis. To investigate the mechanisms of anabolic actions of GH on skeletal muscle growth, we examined the in vitro and in vivo effects of GH on myostatin regulation. Twelve GH-deficient hypopituitary adult subjects were treated with recombinant GH (5 micro g/kg.d) in a double-blind, placebo-controlled fashion. Body composition and physical function were assessed and skeletal muscle biopsies from the vastus lateralis performed at 6-monthly intervals during 18 months of treatment. Myostatin mRNA expression was significantly inhibited to 31 +/- 9% (P < 0.001) of control by GH but not by placebo administration (79 +/- 11%) as determined by quantitative real-time PCR normalized for the housekeeping glyceraldehyde-3-phosphate dehydrogenase gene. The inhibitory effect of GH on myostatin was sustained after 12 and 18 months of GH treatment. These effects were associated with increases in lean body mass and translated into enhanced aerobic performance as determined by maximal oxygen uptake and ventilation threshold. Parallel in vitro studies of skeletal muscle cells demonstrated significant reduction of myostatin expression by myotubes in response to GH, compared with vehicle treatment. Conversely, GH receptor antagonism resulted in up-regulation of myostatin in myoblasts. Given the potent catabolic actions of myostatin, our data suggest that myostatin represents a potential key target for GH-induced anabolism.

Prevalence and pathogenesis of sleep apnea and lung disease in acromegaly

Respiratory disorders are common and important complications in acromegaly. Patients suffering from acromegaly display a 1.6-3.3 fold increase in mortality rate, which is due to respiratory disorders in 25% of cases. In these patients, mortality for lung disease is 2-3 fold higher than in the general population. Every portion of the respiratory system may be involved. Deformities of facial bones, edema and hypertrophy of the mucosae and pharyngeal and laryngeal cartilages, enlargement of the tongue and inspiratory collapse of the hypopharinx, all may contribute to respiratory alterations. Nasal polyps, "hormonal rhinitis", changes of the voice and snoring are common occurrences. Though rarely, a laryngocele may ensue. Pneumomegaly is frequently observed and, as suggested by functional studies, might be due to an increased number rather than volume of the alveoli. An obstructive respiratory syndrome caused by mucosal thickening of the upper airways and bronchi is observed in 25% of female and 70% of male patients. The sleep apnea syndrome (SAS) affects 60-70% of acromegalic patients. SAS may be of obstructive, central or mixed type. Obstructive SAS is the prevailing form in acromegaly. It is due to intermittent obstruction of upper airways with preserved activity of the respiratory center, as testified by the remarkable thoracic and abdominal respiratory efforts. The pathogenesis of the central type of SAS is more complex. Narrowing of the upper airways may induce reflex inhibition of the respiratory center. Moreover, increased GH levels and, possibly, defects in the somatostatinergic pathways, may increase the ventilatory response of the respiratory center to carbon dioxide, thereby leading to respiratory arrest. In the mixed type of SAS, the phenomena underlying the other two forms coexist. Oxygen desaturation concomitant with the apneic episodes accounts for the frequent nocturnal wakening and diurnal drowsiness. Among the clinical correlates of SAS, arterial hypertension is of particular interest due to the close correlation existing between the two disorders. Sleep deprivation related to SAS seems per se to favor the appearance of hypertension. Moreover, short lasting hypoxemia may induce prolonged elevations of blood pressure, mediated by decreased endothelial generation of nitric oxide. Thus, since cardiovascular events are the main cause of mortality in patients with acromegaly, it is reasonable to hypothesize that SAS is involved in the reduced life span of these patients.