Massimo Scacchi

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.

Nutritional status in the neuroendocrine control of growth hormone secretion: The model of anorexia nervosa

Growth hormone (GH) plays a key role not only in the promotion of linear growth but also in the regulation of intermediary metabolism, body composition, and energy expenditure. On the whole, the hormone appears to direct fuel metabolism towards the preferential oxidation of lipids instead of glucose and proteins, and to convey the energy derived from metabolic processes towards the synthesis of proteins. On the other hand, body energy stores and circulating energetic substrates take an important part in the regulation of somatotropin release. Finally, central and peripheral peptides participating in the control of food intake and energy expenditure (neuropeptide Y, leptin, and ghrelin) are also involved in the regulation of GH secretion. Altogether, nutritional status has to be regarded as a major determinant in the regulation of the somatotropin-somatomedin axis in animals and humans. In these latter, overweight is associated with marked impairment of spontaneous and stimulated GH release, while acute dietary restriction and chronic undernutrition induce an amplification of spontaneous secretion together with a clear-cut decrease in insulin-like growth factor I (IGF-I) plasma levels. Thus, over- and undernutrition represent two conditions connoted by GH hypersensitivity and GH resistance, respectively. Anorexia nervosa (AN) is a psychiatric disorder characterized by peculiar changes of the GH-IGF-I axis. In these patients, low circulating IGF-I levels are associated with enhanced GH production rate, highly disordered mode of somatotropin release, and variability of GH responsiveness to different pharmacological challenges. These abnormalities are likely due not only to the lack of negative IGF-I feedback, but also to a primary hypothalamic alteration with increased frequency of growth hormone releasing hormone discharges and decreased somatostatinergic tone. Given the reversal of the above alterations following weight recovery, these abnormalities can be seen as secondary, and possibly adaptive, to nutritional deprivation. The model of AN may provide important insights into the pathophysiology of GH secretion, in particular as regards the mechanisms whereby nutritional status effects its regulation.

Effects of treatment with somatostatin analogues on QT interval duration in acromegalic patients

Objective  Cardiovascular disease is a major contributor to the increased mortality of acromegalic patients. Prolongation of the QT interval is considered an established risk factor for potentially fatal cardiac arrhythmias, an event frequently observed in acromegaly. Changes in ventricular repolarization have been observed with the use of octreotide, one of the somatostatin analogues (SSA) currently used for the medical treatment of this disease. Furthermore, octreotide is listed among the drugs able to prolong the QT interval. Thus, we elected to study the effects of long‐term SSA administration on QT duration and left ventricular mass (LVM) in a group of acromegalic patients.

Clinical relevance of cardiac structure and function abnormalities in patients with Cushing’s syndrome before and after cure.

Objectives  Sustained hypercortisolism impacts cardiac function, and, indeed, cardiac disease is one of the major determinants of mortality in patients with Cushing’s syndrome. The aim of this study was to assess the clinical relevance of cardiac structure and function alterations by echocardiography in patients with active Cushing’s syndrome and after disease remission.

Increased prevalence of prolonged QT interval in males with primary or secondary hypogonadism: a pilot study.

Symptoms and signs of male hypogonadism span all organ systems, including the cardiovascular apparatus. The electrocardiographic QT interval reflects cardiac ventricular repolarization and, if prolonged, increases the risk of malignant arrhythmias. QT interval duration is similar in boys and girls during childhood, but shortens in males after puberty and experimental studies suggest that testosterone is a major contributor to shortening of QT interval in men. The aim of the present pilot study was to assess the duration of ventricular repolarization in adult males with primary or secondary hypogonadism. Standard ECG recordings were performed in 26 men (mean age 39.2 +/- 2.17 years) with pituitary or testicular hypogonadism and repeated in 15 patients during testosterone replacement. Twenty-six age-matched control men were also analysed. Measured QT intervals were corrected for heart rate according to Bazzetts formula (QTc = QT/radical RR interval). The prevalence of prolonged QTc was considerably higher in hypogonadal patients (four of 26 men) than in control men (none, p < 0.05) and in the general, healthy population (<2.5%). QTc interval normalized on hormone replacement therapy in the four patients presenting prolonged QTc in the hypogonadal state. Heart rate and left ventricular mass did not differ among the two groups and no known QT-prolonging factor was apparent in patients with abnormal QTc interval. In conclusion, a high number prolonged QT interval measurements was observed in hypogonadal men who may therefore be at increased risk for cardiac arrhythmias. This observation reveals an additional feature of male hypogonadism, which may benefit from testosterone replacement therapy.

Treatment with biosynthetic growth hormone of short thalassaemic patients with impaired growth hormone secretion

Summary. objective Impairment of linear growth is a common clinical feature In patients with β‐thalassaemia major. Although growth hormone secretion appears to be normal in many short thalassaemic patients, it proves to be deficient in some of them. In these cases, administration of biosynthetic growth hormone seems justified. The aim of this study was to evaluate the effect of such treatment in a group of patients with β‐thalassaemla major presenting with growth failure and impairment of growth hormone secretion.

Bone demineralization in adult thalassaemic patients: contribution of GH and IGF‐I at different skeletal sites

Background and objective  GH and IGF‐I exert an important role in the control of bone formation, as shown by decreased bone mineral density and increased fracture risk in adult hypopituitary patients untreated for GH deficiency (GHD). Different degrees of bone demineralization are frequently reported in patients affected by β‐thalassaemia. Considering the high prevalence of GHD recently observed by our group among adult thalassaemic patients, we elected to study the possible role of GH–IGF‐I abnormalities in the pathogenesis of the osteopenia/osteoporosis of this disease.

Growth hormone deficiency (GHD) in adult thalassaemic patients

Background and objective  Short stature and growth hormone deficiency (GHD) are frequent occurrences in thalassaemic children, while data on the prevalence of GHD in adult patients are lacking. Therefore, we elected to study the growth hormone and insulin‐like growth factor‐I (GH–IGF‐I) axis in a large group of adult thalassaemic subjects.

Ghrelin Stimulates Adrenocorticotrophic Hormone (ACTH) Secretion by Human ACTH‐Secreting Pituitary Adenomas In Vitro

Ghrelin is a brain‐gut peptide with wide‐ranging endocrine, metabolic, cardiovascular and neural effects. Ghrelin, like its synthetic counterparts, the growth hormone (GH) secretagogues, has been shown to markedly stimulate adrenocorticotrophic hormone (ACTH) and cortisol secretion in humans and the ACTH‐releasing effect of GH secretagogues is even greater in patients with pituitary ACTH‐secreting tumours. Furthermore, these tumours synthesize ghrelin itself, suggesting an intrapituitary ghrelin circuit. The aim of the present study was to evaluate the effect of ghrelin on ACTH secretion by human pituitary corticotroph tumours in vitro to test the functionality of this circuit. Nine ACTH‐secreting pituitary tumours (four microadenomas, five macroadenomas) were collected during surgery and incubated with 10–100 nM human ghrelin or with 10 nM human corticotrophin‐releasing hormone (CRH). Control experiments were performed in rat anterior pituitary primary cultures. ACTH secretion was assessed after 4 h and 24 h incubation by immunometric assay. After 4 h of incubation with ghrelin, medium ACTH concentrations were two‐ to ten‐fold higher compared to ACTH concentrations in unstimulated wells. The ACTH‐releasing effect of ghrelin was significantly less than the response elicited by 10 nM CRH (up to 40‐fold) Similar results were obtained after 24 h of incubation and a superimposable response pattern was observed in rat anterior pituitary primary cultures. The present study demonstrates that the endogenous GH secretagogue, ghrelin, stimulates ACTH secretion directly from human tumoural corticotrophs, as well as from normal rat pituitary, and indicates that the marked ACTH release elicited by ghrelin in patients with Cushings disease in vivo is due, at least in part, to its action on the pituitary tumour. However, the reversal of the response pattern reported in vivo, with ghrelin proving a lesser stimulant than CRH in vitro, suggests that additional, suprapituitary mechanisms are involved in the in vivo response. Moreover, these data uphold the concept of a functional intratumoural ghrelin paracrine circuit in human corticotroph adenomas.

Elastosonographic evaluation of thyroid nodules in acromegaly

OBJECTIVE Ultrasound-elastography (US-E) appears to be a helpful tool for the diagnosis of thyroid cancer. In acromegaly, the prevalence of thyroid cancer is still debated. The aims of this study were to evaluate thyroid nodules in acromegaly and to establish the accuracy of US-E in providing information on their nature, using cytological analysis as a reference. SUBJECTS AND METHODS US-E was applied to 90 nodules detected in 25 acromegalic patients and to 94 nodules found in 31 non-acromegalic goitrous subjects. The lesions were classified according to the elasticity scores (ES) as soft (ES 1-2) or hard (ES 3-4). Fine needle aspiration cytology could be performed in 60.8% of hard nodules in acromegalics and in 86.7% of hard nodules in controls. RESULTS The prevalence of hard nodules was significantly higher in the whole group of acromegalic patients than in controls (56.8 vs 16.0%, P<0.0001). The prevalence of hard nodules in patients with active acromegaly (68.9%) was greater, though not to a statistically significant extent, than that observed in cured (44.4%) and controlled (52.5%) patients. Cytology revealed malignancy or suspect malignancy in four of the nodules of non-acromegalic subjects and in none of the nodules of acromegalic patients. CONCLUSIONS This study has demonstrated a high prevalence of stiff thyroid nodules in acromegaly, greater than that found in non-acromegalic goitrous subjects. In acromegalics, hard nodules appeared not to be malignant on cytopathological examination and are probably of fibrous nature. Thus, US-E appears to be of limited value for the diagnosis of thyroid cancer in acromegaly.