Serum immunoreactive trypsin in beta-thalassaemia major

Pancreatic iron quantification with MR imaging: a practical guide

Accurate determination of pancreatic iron status is crucial for preventing impairment of the exocrine and endocrine function of the pancreas and for prospectively stratifying the cardiac iron risk. The following article should be a sort of practical guide for radiologists interested in quantifying pancreatic iron overload by Magnetic Resonance Imaging (MRI). After a brief background on iron-deposition diseases, we will describe basic principles and relative advantages and disadvantages of the more widely used and clinically feasible MRI-based techniques for pancreatic iron assessment. These methods can be classified into signal intensity ratio (SIR) and relaxometry methods. We will examine different technical aspects representing the key for accurate and precise relaxation time measurement.

Iron metabolism and the exocrine pancreas

Although the pathophysiological mechanisms and consequences of gross derangements in iron metabolism are well known, little is known about the pathophysiological mechanisms underlying mild-to-moderate alterations in iron metabolism and their consequences. Growing evidence indicates that the exocrine pancreas has a bidirectional relationship with iron metabolism. Studies have shown alterations in circulating markers of iron metabolism, iron absorption, and intra-pancreatic iron deposition in pancreatitis. At the same time, exocrine pancreatic dysfunction has been shown in iron overload disorders. These observations reveal a compelling connection between the exocrine pancreas and iron metabolism, which are further elucidated by observations of therapeutic benefits of iron chelating agents and pancreatic enzyme replacement therapy. While the pancreas is not a major reservoir of iron in the body, better understanding of its relationship with iron metabolism may yield unexpected insights.

Monitoring changes in plasma levels of pancreatic and intestinal enzymes in a model of pancreatic exocrine insufficiency--induced by pancreatic duct-ligation--in young pigs

PURPOSE

Plasma levels of pancreatic and intestinal enzymes were measured after pancreatic duct ligation (PDL) to monitor pancreatic exocrine insufficiency (PEI) in a model using young pigs.

MATERIAL/METHODS

Five, 6 week-old pigs (10.9±0.2kg), underwent PDL while age-matched, un-operated pigs were used as controls. Plasma levels of immunoreactive cationic trypsinogen (IRCT), amylase, lipase, and diamine oxidase (DAO) activities were analyzed for 48 days after PDL, including 1 week of oral pancreatic enzyme supplementation (PES) with Creon(®).

RESULTS

PDL resulted in an arrested body growth and a rapid surge of pancreatic enzymes (IRCT, amylase and lipase) into the plasma. Nine days after PDL, the plasma levels of these pancreatic enzymes had decreased. IRCT then remained below the level in un-operated pigs while amylase only fell below control at 25 days. The intestinally derived marker DAO and plasma protein levels were unaffected by PDL but DAO decreased slightly with time in PEI pigs. One-week of oral PES restored body growth, but had little effect on pancreatic enzyme plasma levels, except for a tendency towards increased DAO.

CONCLUSIONS

The study showed that PEI developed within 1-2 weeks after PDL and that only IRCT is a reliable plasma enzyme marker for this. The reduced plasma DAO indicated that PEI also affected the intestines, while PES therapy restored growth of the PDL pigs and slightly increased plasma DAO, suggesting an improved intestinal function.

Ultrasonography of the pancreas, as a function index, in children with beta-thalassemia

Increased echogenicity of the pancreas, due to hemosiderosis, is a frequent laboratory finding in children and adolescents with beta-thalassemia. The aim of this study was to investigate whether increased echogenicity of the pancreas is associated with dysfunction. The ultrasonic image of the pancreas was examined in 34 children aged 12+/-3.8 years old and was compared to the endocrine and exocrine functioning of the gland. Oral glucose tolerance test (OGTT) was performed with simultaneous measurement of insulin and serum trypsin. Twenty-six of the 34 patients (76.5%) presented increased echogenicity, while 8 (23.5%) had a normal ultrasonic pancreatic image. 77% of the patients with increased echogenicity had abnormal OGTT, 46%, with subnormal or increased insulin values, and 32.5% manifested low levels of trypsin. Among the patients with normal ultrasound, 25% had abnormal OGTT and 37.5% abnormal insulin values. Statistical analysis with Student's t-test revealed that patients with increased echogenicity had significantly higher glucose values on OGTT at 60: 7.6 +/- 1.8 mmol/l (137.3 +/- 33.7 mg/dl) as compared to the patients with normal ultrasound: 6.1 +/- 1.2 mmol/l (110.75 +/- 21.72 mg/dl) (p<0.05). Insulin values were significantly affected at 30, 60, and 90 min: 570+/-301, 332+/-156, 294+/-158 pmol/l (79.54 +/- 42, 46.4 +/- 21.8, 41.04 +/- 22 mU/l) respectively in patients with increased echogenicity in comparison to those with normal ultrasonographic image of the gland: 301 +/- 170, 192 +/- 52, 135 +/- 63 pmol/l (42 +/- 23.7, 26.85 +/- 7.36, 18.9 +/- 8.8 mU/l) (p<0.05). No statistical significance was observed between the two groups regarding trypsin levels, even though abnormal values were observed in more children with increased echogenicity than in patients with a normal ultrasound. The above findings confirm that increased echogenicity of the pancreas is associated with disturbance of its function. This simple imaging method could be used as a rough early index of detection of an increased risk for developing diabetes mellitus in patients with beta-thalassemia.

Serum and fecal pancreatic enzymes in beta-thalassemia major

CONCLUSION

This study, using indirect tests, demonstrated that exocrine pancreatic function is impaired in a proportion of patients with beta-thalassemia major (TM), though this impairment is generally mild or moderate.

BACKGROUND

Impaired structure and function of the exocrine pancreas has been reported in patients with Beta-thalassemia major.

METHODS

In this study we measured fecal fats and serum and fecal pancreatic enzymes in 30 patients (13 M, 17 F) with TM, mean age 22.1 yr (range 14-39) and compared them with those of a matched group of healthy controls. Results were correlated with age, serum ferritin, blood transfusion, and various nutritional parameters. Enzymes assays included: serum pancreatic amylase (PA), lipase (L), trypsin (T), fecal chymotrypsin (FCT), and fecal elastase (FE).

RESULTS

No patient was positive for steatorrhea. Comparison of the mean values showed a significant difference only for FE (p < 0.002). Using only the fecal tests as a reference, we found that 12 patients had FE values below the cutoff limit; of these, five had values between 100 and 185 micrograms/g, three between 50 and 99 micrograms/g and four below 50 micrograms/g. Ten patients had FCT values below the cutoff limit; seven presented impairment in both tests and six of them had FE values below 100 micrograms/g (including four diabetics). No correlations were found between enzyme values and mean serum ferritin values or mean blood consumption over the previous 3 yr. No correlation was found between FE and FCT levels or between enzymes and age.

Clinical manifestations and therapy of transfusional haemosiderosis

Long-term blood transfusions lead to the accumulation of iron that in the absence of chelation therapy causes complications such as liver cirrhosis, growth failure, hypogonadism, hypothyroidism, hypoparathyroidism, diabetes and myocardiopathy. The last still represents the most frequent cause of death in haemosiderotic transfusion-dependent patients. At the moment the only chelator widely used is desferrioxamine (DFX). The drug works best when administered as a continuous infusion, mainly by the subcutaneous route. To patients with severe iron overload, impending organ failure, or poor compliance to chelation, DFX can be administered intravenously, through an externalized central catheter or, preferably, a subcutaneous port. Several studies have shown the effectiveness of DFX in reducing the iron burden, thus preventing the complications, once considered inevitable, of iron overload, and even in reverting some, but not all, of the iron-induced dysfunctions. Practical and psychological support are necessary to ensure satisfactory compliance with a therapy that is cumbersome and difficult. Toxic effects of DFX such as growth failure, hearing impairment and bone abnormalities seem to occur mainly in patients who have received high doses of DFX despite a low iron burden. Visual loss and renal and pulmonary toxicities, on the contrary, seem to be more directly related to high DFX peak doses administered irrespective of the patient's amount of iron overload. After bone marrow transplantation, phlebotomy or erythrocytoapheresis might be necessary to reduce further the iron accumulated during years of transfusions.

Biochemical tests in the diagnosis of chronic pancreatitis and in the evaluation of pancreatic insufficiency

Chronic pancreatitis (adults) and cystic fibrosis (children) are the most common diseases leading to exocrine pancreatic insufficiency that, when reduced to < 5% of normal function, is characterised by steatorrhoea. The pathogenesis of the former condition is outlined, and recent concepts are emphasized. Biochemical tests to detect pancreatic insufficiency and to identify pancreatic disease as the cause of steatorrhoea include: serum enzyme tests (lipase, amylase, trypsin); stool chymotrypsin; isotopic tests based upon the assimilation of [14C] lipids and starch or excretion of the isotope as breath CO2, as well as the dual-labelled Schilling test; oral function tests utilising substrates hydrolysed by pancreatic enzymes such as benzoyl tyrosyl-p-aminobenzoic acid and fluorescein dilaurate; and duodenal intubation studies following meal-induced or hormonal stimulation of the pancreas. The rationale for these tests and the cumulative clinical experience of their utility are reviewed. A recommended diagnostic strategy is briefly presented. The role of various biochemical procedures to evaluate the efficacy of pancreatic enzyme replacement therapy is also described.

Serum immunoreactive trypsin in tropical pancreatic diabetes syndrome

Fifteen patients with tropical pancreatic diabetes syndrome (TPDS), 16 insulin-dependent diabetics (IDD), 27 non-insulin-dependent diabetics (NIDD) and 14 normal subjects, all from India, were investigated for markers of beta-cell (C-peptide) and exocrine (immunoreactive trypsin; IRT) reserve. IRT and C-peptide concentrations were the lowest in TPDS, lower than normal in IDD, and not significantly different from normal in NIDDs. There was a highly significant correlation (rs = 0.93; P less than 0.0001) between IRT and C-peptide (measured in 50% of patients and controls) concentrations when all diabetic groups were combined. Such a correlation was absent when TPDS patients were considered in isolation, largely because of the markedly low IRT concentration. Fourteen of 15 patients (93%) with TPDS had subnormal IRT concentrations, of which 11 had IRT values of less than 50 micrograms/L. These IRT values are similar to those previously reported in cystic fibrosis. Only 6 of 16 IDDs (38%) had subnormal IRT concentrations, of which only one was below 50 micrograms/L. These data suggest that exocrine pancreatic reserve is markedly diminished in TPDS and that a subnormal IRT concentration may be a useful biochemical marker for this form of diabetes.

Serum immunoreactive trypsin and pancreatic lipase in primary biliary cirrhosis

Immunoreactive trypsin concentration and pancreatic lipase activity were measured in the sera of 33 patients with primary biliary cirrhosis. Immunoreactive trypsin was increased (above the normal range) in 16 (48%) and pancreatic lipase activity in 18 (55%) patients. Both enzymes were increased in 10 (30%) patients. Twenty four patients (73%) had an increase of either one or both enzymes. There was a significant correlation between immunoreactive trypsin and pancreatic lipase activity. This abnormality was not related to treatment with D-penicillamine, the age of the patients, the stage of the disease, or the severity of cholestasis. Thus most patients with primary biliary cirrhosis have increased pancreatic enzyme activity and immunoreactive trypsin concentration in their sera. These data are indicative of damage to the exocrine pancreas. The cause of this damage is as yet unknown.

The sicca syndrome in thalassaemia major

A 20 year old man with beta thalassaemia developed symptoms of the sicca syndrome. His serum contained rheumatoid factor and antinuclear antibodies. A biopsy specimen of labial salivary gland showed large accumulations of haemosiderin within the parenchymal cells of the acini. Although in this case the sicca syndrome could not be definitely distinguished from Sjögren's syndrome, the patient's HLA type was not the one usually associated with Sjögren's syndrome. Histological appearances suggested that the causative factor of the sicca syndrome was iron overload owing to an intensive blood transfusion regimen.

Serum pancreatic enzymes in the elderly

Immunoreactive trypsin (IRT) and pancreatic lipase were measured in serum from 37 geriatric in-patients (median age 77.5 years) without history of diarrhoea, pancreatic disease, diabetes or acute or chronic alcoholic intake. IRT and pancreatic lipase concentrations/activity were strongly correlated and were markedly elevated when compared with a control population of 22 subjects (median age 27 years). Such elevations in pancreatic enzymes indicate a subclinical damage of exocrine pancreatic tissue. Assessment of exocrine pancreatic function in the geriatric age group should not be based on pancreatic enzyme levels in serum.

Exocrine pancreatic function in diabetes mellitus

An investigation of serum immunoreactive trypsin concentration and pancreatic isoamylase activity in patients with diabetes mellitus has shown that exocrine pancreatic deficit is maximal in insulin dependent diabetics, intermediate in those controlled with sulphonylureas, and absent in patients controlled with biguanides or diet or both. A significant correlation between the serum concentrations of both these pancreatic enzymes and C peptide was found. Serum pancreatic enzyme concentrations were not related to glycosylated haemoglobin concentrations, the dosage of insulin, or the age of onset of diabetes. The concentration of immunoreactive trypsin was found to be low in most of the insulin dependent diabetics in whom this enzyme was measured at the time of the clinical onset of diabetes. Thus exocrine pancreatic deficit in diabetes closely parallels the endocrine beta cell deficit and occurs concurrently with, or antedates, the clinical presentation of type I diabetes. It is therefore possible that in type I diabetes similar mechanisms are entailed in the pathogenesis of impaired endocrine and exocrine pancreatic function.

Serum pancreatic lipase activity in cystic fibrosis

Patients with cystic fibrosis have been found to have abnormal serum concentrations of immunoreactive trypsin and abnormal activities of pancreatic isoamylase. A study was undertaken to discover whether activity of pancreatic lipase is also altered in cystic fibrosis. Serum from 23 patients with cystic fibrosis was assayed for immunoreactive trypsin and pancreatic lipase. Median serum pancreatic lipase activity was significantly lower in patients with cystic fibrosis than in controls, as was immunoreactive trypsin concentration (p less than 0.0001). Some patients had supranormal lipase concentrations but these were not always associated with absence of malabsorption. Serum pancreatic lipase activity is considerably changed in cystic fibrosis.

Low pancreatic lipase in insulin-dependent diabetics

Serum samples obtained from 20 insulin-dependent diabetics (IDD), 23 non-insulin-dependent diabetics (NIDD) and 30 controls were assayed for their pancreatic lipase activity, immunoreactive trypsin concentration and glycosylated haemoglobin (HbA1) respectively. The distribution of serum pancreatic lipase activity in normal subjects and diabetics was nonparametric. The median serum lipase activity in IDDs (86 U/l) was significantly lower that that in controls (131 U/l, p less than 0.002) and NIDDs (126 U/l, p less than 0.001). There was a significant correlation between serum pancreatic lipase activity and serum IRT concentration (r = 0.65, p less than 0.001). Neither pancreatic lipase activity nor IRT was related to HbA1 concentrations. These data show for the first time that serum pancreatic lipase activity is diminished in IDDs.