Adenosine stress protocols for nuclear cardiology imaging

The treadmill test combined with myocardial perfusion imaging (MPI) is a commonly used technique in the assessment of coronary artery disease (CAD). However, there is a group of patients who may not be able to undergo the treadmill test. Pharmacologic stress testing is increasingly utilized for stress perfusion imaging and currently accounts for nearly 40% of all nuclear stress testing [8]. The aim of this study was the introduction of adenosine stress protocols in our nuclear laboratory, and the following, recording and comparing of the frequency and severity of side-effects.

METHODS

We performed two kinds of adenosine stress protocols on 186 patients who underwent MPI with radiotracer 99mTc-sestamibi: 1st: 47 patients underwent AdenoSCAN abbreviated protocol IV. adenosin 140microg/kg/min for 3 minutes; 2nd: AdenoEX combined with low level 50W bicycle exercise in 139 patients. We followed and compared side-effects (minor and major events) between AdenoSCAN and AdenoEX protocol, and established an adequate time for imaging of both protocols.

RESULTS

Compared with AdenoSCAN, AdenoEX protocol was tolerated by all patients; it reduced all side-effects and improved image quality. Using AdenoEX protocol we found that the heart-to-liver ratio was significantly better, and we established a time of imaging of 15 minutes after stress, compared to the AdenoSCAN time of imaging which was a minimum of 45 minutes after stress.

CONCLUSION

This study gives advatages to AdenoEX protocol, because it had fewer side-effects, improved patients' tolerance, improved image quality, and enhanced efficiency and throughput given the opportunity for earlier imaging.

[Clinical study of administration of abciximab--a monoclonal antibody to platelet glycoprotein IIb/IIIa in percutaneous intracoronary interventions]

During the last 10 years a new group of drugs was developed--platelet glycoprotein IIb/IIIa blockers that is nowadays largely and efficiently used as for the prevention of percutaneous coronary intervention complications as well as in the treatment of acute coronary syndromes. In the period February-June 2000--19 patients (18 males, 1 female, of average age 53.3 years) were administered Abciximab in the bolus dose of 10 mg immediately before the intervention and afterwards 10 mg by 12-hour infusion. All patients received aspirin and ticlopidine hydrochloride if the stent was introduced and heparin by the standard protocol. Elective intervention was done in 17 patients (non-Q infarction in 3 patients, unstable angina pectoris in 5 patients, postinfarction angina pectoris in 2 patients, acute myocardial infarction at least 1 month before the intervention in 6 patients and 1 patient with myocardiopathy) and in 2 patients the intervention was performed during the myocardial infarction. In 15 patients (79%) intracoronary stent was introduced and in 5 patients (21%) the intervention was performed on 2 arteries. Maximal immediate effect of the dilatation was achieved in 18 patients (94.7%). In the first 60 days of the follow-up 1 patient (5%) died of some other disease, and in no patients symptomatic myocardial ischemia was found. No adverse effects were observed.

GH-releasing hormone and GH-releasing peptide-6 for diagnostic testing in GH-deficient adults

BACKGROUND

The diagnosis of growth hormone (GH) deficiency in adults is based on provocative testing of GH secretion. The insulin tolerance test (ITT), currently the favoured test for this diagnosis, has been criticised for poor reproducibility and inconvenience. Since the combined administration of GH-releasing hormone (GHRH) plus GH-releasing peptide-6 (GHRP-6) is the most potent stimulus of GH secretion, we did a multicentre study comparing GH peaks elicited by ITT with those elicited by the GHRH/GHRP-6 test in healthy controls and GH-deficient individuals (cases).

METHODS

125 adult patients with organic pituitary disease and 125 healthy individuals were studied. All cases and controls were given GHRH 1 microg per kg bodyweight intravenously plus GHRP-6 1 microg per kg intravenously at 0 min and blood samples were obtained during a subsequent 120 min period. 27 controls and all cases had an ITT. Inclusion criteria were severe GH deficiency--ie, a GH peak after ITT of < or = 3 microg/L. Results of the GHRH/GHRP-6 test were analysed by receiver-operating characteristic curve methodology.

FINDINGS

GH peaks seen after the GHRH/GHRP-6 test did not result in any side-effects and were not affected by age, sex, amount of adipose tissue, or by the GH assay system used. The GH mean peak after the GHRH/GHRP-6 test was 59.2 microg/L (SD 2.2) for controls and 4.1 microg/L (0.3) for cases, whereas after ITT the mean peak was 14.3 microg/L (1.7) and 0.5 microg/L (0.06), respectively. The differential peak responses of controls and cases was greater (p<0.001), for GHRH/GHRP-6 test than for ITT. When individually analysed GH peaks were a continuum, from 139.0 microg/L to 0.01 microg/L, with a cut-off point of 15.0 microg/L. The GHRH/GHRP-6 test performed well under the ROC curve analysis. For clinical utility, it is then proposed that values > or = 20.00 microg/L be considered normal and < or = 10.00 microg/L as GH deficient.

INTERPRETATION

The GHRH/GHRP-6 test is a convenient, safe and reliable test for adult GH deficiency and is not confounded by clinical factors known to alter GH secretory patterns. An evoked GH concentration of > or = 15.0 microg/L accurately distinguishes between healthy and GH-deficient adults.

Increased incidence of neoplasia in patients with pituitary adenomas. The Pituitary Study Group

OBJECTIVE

The goal of our study was to determine the rate of neoplasms in patients with other pituitary adenomas (non-functioning and prolactinomas) in comparison with acromegaly which is known to favour the development of neoplasia.

DESIGN AND PATIENTS

We reviewed clinical records for 220 patients with acromegaly, 151 patients with non-functioning pituitary adenoma (NF) and 98 patients with prolactinomas. Incidence rates of cancer for patients with pituitary tumours were calculated per person-years of follow-up study. These rates were then compared with sex and age adjusted incidence rates reported by National Tumour Registry. An internal control group of 163 subjects with a non-neoplastic condition, i.e. Graves' disease followed chronically in the same clinic was also studied. The ratios observed to expected were expressed as standardized incidence rates (SIR). The only significant difference between the acromegalic and other pituitary tumours patients was in hypopituitarism, present in 18.2% (acromegaly) 47% (NF) and 18.6% (prolactinomas).

RESULTS

Twenty-three malignant tumours were registered in 19 acromegalics (1 Hodgkin disease, 1 myelogenous leukaemia, 1 lymphocytic leukaemia, 3 papillary thyroid carcinomas, 1 ovarian carcinoma, 2 colorectal carcinoma, 1 renal cell carcinoma, 4 cervical carcinoma, 2 skin cancers, 2 pancreatic carcinoma, 4 breast carcinoma, 1 bladder carcinoma). Three acromegalics harboured two malignancies. Patients with acromegaly had a 3.39-fold increased rate of malignant tumours compared with the general population and a 3.21-fold increased rate compared with our internal control group. Eleven malignant tumours were found in patients with NF-pituitary adenomas and 2 in prolactinoma patients (1 lymphoma, 1 multiple myeloma, 1 colonic cancer, 1 renal cell cancer, 1 stomach cancer, 2 lung cancers, 1 cervix carcinoma, 1 breast cancer, 1 testicular carcinoma and 3 melanoma). Patients with NF pituitary adenomas had a 3.91-fold increased rate of malignant tumours compared with the general population and 4.07-fold increase compared with the internal control group. Patients harbouring prolactinomas did not have an increased incidence rate of malignancy compared with the general population or our internal controls. Female patients with acromegaly and male patients with NF-pituitary adenoma had higher incidences of neoplasia.

CONCLUSION

We have demonstrated that the overall incidence of malignant tumours in patients with non-functioning pituitary adenomas and acromegaly is significantly higher than expected for general population and for our internal control group.

Growth hormone secretion elicited by GHRH, GHRP-6 or GHRH plus GHRP-6 in patients with microprolactinoma and macroprolactinoma before and after bromocriptine therapy

OBJECTIVE

Growth hormone-releasing peptides (GHRPs) are potent GH releasers which act at both pituitary and hypothalamic levels through specific G-protein coupled receptors, recently cloned. A synergistic effect from the simultaneous administration of GHRH + GHRP-6 on GH release is observed in normal subjects, while it is absent in patients with hypothalamo-pituitary disconnection. We studied the effects of GHRH, GHRP-6 and both secretagogues on GH release in patients harbouring pituitary tumours that may be reduced in size by medical treatment.

DESIGN

Analysis of peak GH response to GHRH, GHRP-6 and GHRH plus GHRP-6 in patients with micro- and macroprolactinomas. Integrated GH response over 2 hours calculated as AUG-GH mU/l x 120 min. Analysis of delta PRL above the basal level in response to the same GH releasers.

PATIENTS

Eleven patients with macroprolactinomas aged 41.2 +/- 4.8 years (range 24-75), nine patients with microprolactinomas aged 31.5 +/- 3.4 (range 22-53) and 13 healthy subjects aged 42.1 +/- 4.7 years (range 22-64) were studied. Prolactinoma patients were then treated with bromocriptine (15-20 mg orally) for 6-24 months. Tests were repeated when there was evidence of tumour shrinkage and normalized plasma prolactin concentrations.

RESULTS

Peak GH response before treatment in macroprolactinoma patients was 4.9 +/- 0.9 mu/l after GHRH, 8 +/- 4 mU/l after GHRP-6 and 18 +/- 5 mU/l after GHRH + GHRP-6. Synergism was absent. AUC were 390 +/- 90; 500 +/- 100 and 1100 +/- 300 mU/l x 120 min respectively. These values were all significantly different (P < 0.05) from normal subjects and patients with microprolactinomas with peak GH 16.8 +/- 0.9 mU/l after GHRH; 43 +/- 6 mU/l after GHRP-6 and 130 +/- 10 mU/l after GHRH + GHRP-6. AUC-GH was 1200 +/- 400 after GHRH, 2200 +/- 400 after GHRP-6 and 9000 +/- 1000 mU/l x 120 min after GHRH + GHRP-6. As in normal subjects, synergism was preserved in patients with microprolactinoma (P > 0.05). After treatment with bromocriptine peak GH in patients with macroprolactinoma was 8 +/- 4 mU/l after GHRH, 22 +/- 5 mU/l after GHRP-6 and 70 +/- 20 mU/l after GHRH + GHRP-6. AUC-GH was 800 +/- 300, 1100 +/- 300 and 3500 +/- 800 mU/l x 120 min, respectively. The response of GH after GHRP-6 and GHRH + GHRP-6 improved significantly (P < 0.05) in treated patients with macroprolactinoma. There was no significant change in GH response in microprolactinoma patients after treatment with bromocriptine. Peak GH after GHRH was 30 +/- 20 mU/l, after GHRP-6 it was 75 +/- 8 mU/l and after GHRH + GHRP-6 it was 200 +/- 30 mU/l. AUC-GH was 1500 +/- 700 after GHRH, 4500 +/- 500 after GHRP-6 and 15,100 +/- 600 mU/l x 120 min. Delta prolactin after GHRP-6 did not change before and after bromocriptine treatment in patients with macroprolactinoma or microprolactinoma.

CONCLUSION

GH release after GHRP-6 or GHRH + GHRP-6 is fully preserved in patients with microprolactinomas and does not differ before and after treatment with bromocriptine. Patients with macroprolactinoma have blunted responses of GH after GHRH and GHRP-6 and synergism is severely compromised. GH responsiveness to and synergistic interaction between GHRH and GHRP-6 recovers after shrinkage of macroprolactinoma with bromocriptine. Prolactin release stimulated by intravenous administration of GHRP-6 in healthy subjects was not seen in patients with micro- or macroprolactinomas.

Serum leptin and insulin concentrations in patients with insulinoma before and after surgery

Inferential studies suggest that circulating insulin concentrations positively regulate leptin secretion by adipocytes. In humans, however, insulin requires prolonged periods of time, and relatively artificial set-ups before a relationship with leptin can be observed. In the present work, serum leptin concentrations were measured in five patients with insulinoma before and one month after surgery and in five control subjects matched by sex and body mass index (BMI). The control subjects presented a mean serum leptin concentration of 6.7+/-1.5 microg/l and a BMI of 24.9+/-1.1. The mean serum leptin concentration in patients with insulinoma was 11.8+/-3.1 microg/l (P < 0.05 vs controls), with a BMI of 26.3+/-1.9. After surgery, there was a non-significant reduction in BMI (25.8+/-1.7), and a clear reduction in serum leptin concentration (5.6+/-2.4 microg/l, P < 0.05 vs pre surgical values and no difference vs control subjects). The fasting area under the curve (AUC) of insulin concentration (in mU/l per 120 min) before surgery was 14421+/-4981 and after surgery was 1306-/+171 (P < 0.05). Before surgery, serum leptin concentrations significantly correlated with BMI (r = 0.71) and AUC of insulin (r = 0.82), a correlation that was lost after surgery. In conclusion, serum leptin concentrations are significantly elevated in patients with chronically high insulin levels due to insulinoma. After surgical treatment and normalization of insulin values, leptin levels return to normal.

Growth hormone secretagogues in pathological states: diagnostic implications

The identification and cloning of the receptor for synthetic growth hormone (GH) secretagogues, even before the endogenous ligand has been identified or its precise physiological role established, suggests that there is a novel target of action for this class of drug. In an attempt to select patients who will benefit from GH treatment, GH secretagogues are being evaluated for their usefulness in diagnosing GH deficiency. The effects of GH-releasing peptides (GHRPs) on GH release as a function of age and metabolic status, and in different neuroendocrine pathologies, are described, as are the different mechanisms of action, potency and reproducibility of the response to GHRPs compared with GH-releasing hormone (GHRH). GHRPs offer the advantage over GHRH in natural models of deranged GH secretion in that, in various metabolic states (e.g. obesity, anorexia nervosa and non-insulin-dependent diabetes mellitus), the GH response to GHRH is more impaired than it is to GHRPs. However, in some neuroendocrine pathologies, the reverse is true. Thus, both secretagogues provide separate information on the physiological status of somatotrophs.

Absence of desensitization by hexarelin to subsequent GH releasing hormone-mediated GH secretion in patients with anorexia nervosa

OBJECTIVE

Both the basal levels and the neuroregulation of GH secretion are perturbed in patients with anorexia nervosa. It is unknown if these alterations are due to severe undernutrition or if they reflect basic neurotransmitter alterations of the patient's neural pathways. On the other hand, prior administration of the GH secretagogue hexarelin in normal subjects blocks the GH-releasing capability of GH releasing hormone (GHRH) administered 2 hours later. In the present work a sequential test was performed using the administration of hexarelin as first stimulus followed 120 minutes later by GHRH. The two aims of the study were: (a) to evaluate the interaction of GHRH and hexarelin, and (b) to further understand the alterations in GH neuroregulation in patients with anorexia nervosa.

DESIGN

The GH stimuli used were hexarelin (1 micrograms/kg i.v.), a GH stimulus whose main action is hypothalamic, followed 120 minutes later by GHRH (1 micrograms/kg i.v.) as a pituitary stimulus. Each woman was tested once.

PATIENTS

Thirty-two woman matched for age participated in the study: six normal-weight women as controls, 14 women with anorexia nervosa, seven women with secondary amenorrhoea due to voluntary weight loss for aesthetic reasons, and five normal-weight women after 72 hours of a controlled hypocaloric diet (800 cal/day).

MEASUREMENTS

Plasma GH levels were measured by time-resolved fluoroimmunosasay, each value shown is the mean +/- SE in mU/l.

RESULTS

The administration of hexarelin to the normal-weight women induced a clear-cut GH secretion (expressed as mean +/- SE of GH peak in mU/l of 77.5 +/- 21.8, but blocked the GH-releasing capability of GHRH administered 120 minutes later (6.6 +/- 2.8, P < 0.05). In contrast, the women with anorexia nervosa showed a normal GH response after the two stimuli: hexarelin 64.8 +/- 9.2. GHRH 71.1 +/- 14.2. The absence of heterologous desensitization was specific to anorexia nervosa, because the women with amenorrhoea due to voluntary weight loss but with a normal energy intake showed a pattern similar to the controls (GH after hexarelin 60.3 +/- 9.5 and to GHRH 120 minutes later 6.2 +/- 1.0 (P < 0.05)). Similarly, the women after the short-term hypocaloric diet showed a hexarelin-mediated GH secretion of 99.6 +/- 17.8, which blunted the subsequent administration of GHRH (GH mean peak of 9.9 +/- 2.9, P < 0.05 vs hexarelin).

CONCLUSIONS

In the normal subjects, the administration of hexarelin induced clear-cut GH secretion, but inhibited the action of GHRH when administered 120 min later, while this heterologous desensitization was not observed in the patients with anorexia nervosa. This sequentially delayed test may be of some value in the clinical setting for assessing the status of patients with anorexia nervosa.