الفهرس 
AIM OF THE WORKOnly 14 pages are availabe for public view
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Abstract
It has been now 16 years since the hepatitis C virus was first identified in 1989. Tremendous progress has been made to understand and treat HCV. The disease is surprisingly complex in its manifestations and complications whether hepatic or extrahepatic. The mechanisms of liver pathogenesis are not fully understood. It is well established that innate and specific immune responses to the presence of the replicating virus play a central role in liver pathogenesis. Current treatment is poorly tolerated and achieves viral clearance in less than half of the patients. Thus, the end result of deficient knowledge about pathogenesis and lack of effective treatment of HCV is hindrance of its control and persistence of infection with liability to development of complications.
Bone loss is one of the complications associated with chronic hepatitis C. It is a dynamic tissue removal and replacement throughout the lifetime of the individual. Bone formation and resorption are tightly linked processes particularly in young adults. However, with increasing age, bone formation does not keep pace with resorption and bone mass is gradually lost.
Bone formation is the function of osteoblasts, which produce large numbers of proteins including osteonectin, proteoglycans, sialoprotein and osteocalcin. The production of these proteins along with collagen matrix and the precipitation of calcium and phosphate result in bone formation.
In contrast, bone resorption is performed by osteoclasts, which cause demineralization of bone and degradation of its matrix. Bone formation and resorption occurs in cortical & cancellous bones. Cells which share in this process are called multicellular units.
Nevertheless, little is known about bone mass and its metabolism in viral cirrhotic patients. Different factors may be involved in the pathogenesis of osteoporosis in HCV infection including IGF-1 deficiency, hyperbilirubinemia, hypogonadism, subnormal vitamin D levels or its receptor genotype alteration, OPG deficiency, PTH and calcitonin hormones level changes, low vitamin K, diuretic use, interferon and ribavirin administration, poor nutrition, impaired absorption, reduced muscle mass and immobility.
PTH is a hypercalcemic hormone secreted by the parathyroid glands. It is composed of 84 amino acids. Kupffer cells in the liver metabolize intact hormone and parathyroid glands play another role in its degradation. Moreover, kidneys are responsible for PTH clearance after its destruction. PTH regulates extracellular calcium concentration by directly stimulating bone resorption, calcium reabsorption in the kidneys and intestine and by its stimulatory synthetic effects of 1,25 hydroxycholecalciferol in kidneys. Secondary hyperparathyrodism has been reported as a possible cause of hepatic osteoporosis due to its bone resorptive effect. However, there is great controversy about the role of parathormone in hepatic osteodystrophy.
Some authors detected elevation of PTH value in hepatic osteoporosis, others observed low levels and few researchers reported no change in PTH levels in end stage hepatic osteoporosis.
The role of calcitonin in hepatic osteoporosis and treatment is also conflicting. It is a hypocalcemic peptide secreted from C cells of the thyroid gland. It consists of 32 amino acids. Calcitonin is metabolized mainly in the kidneys. It acts as the physiological antagonist of PTH, primarily by inhibiting osteoclasts mediated bone resorption and secondarily by enhancing renal calcium clearance. In some studies, the authors described high levels of calcitonin, while others found no hormone difference in cirrhotic patients when compared with their controls. Moreover, calcitonin administration in postmenopausal women with osteoporosis leads to reduction of bone loss in both vertebrae and hips. However, its effect on decreasing fracture incidence or bone pains in hepatic osteoporosis is conflicting and has not yet been completely understood.
Accordingly, the aim of the present work was to evaluate the possible role of parathyroid and calcitonin hormones in hepatic osteoporosis secondary to chronic hepatitis C infection.
The present study was conducted on 45 chronic hepatitis C patients. They were divided equally into 3 groups (each made of 15 patients) according to the modified Child-Pugh score. Moreover, 15 healthy age and sex matched volunteers were enrolled in this work for comparison.
All included patients and controls were subjected to full history taking and clinical examination looking for other possible etiologies of osteoporosis other than HCV for exclusion. In addition, urine & stool analysis were carried out. Rectal snip biopsies were done for suspected cases of schistosomasis to exclude positive ones. Moreover, blood samples were taken to perform complete blood picture, renal function tests (blood urea and creatinine), fasting and post-prandial blood sugar, ESR, HBsAg and core antibody.
Selected patients and controls were further subjected to liver function tests (serum transaminases, total protein, albumin, prothrombin time & activity and total bilirubin), HCV antibody by third generation ELIZA. Positive cases were confirmed by PCR and abdominal ultrasonography. Liver biopsies were also done whenever possible.
Moreover, patients & controls were investigated for diagnosis of the etiology and the effect of osteoporosis on bones by determination of serum and urinary calcium, phosphorus and magnesium by colorimetric method. Ionized calcium was calculated through its equation. In addition, PTH was assayed by chemiluminescence, calcitonin and urinary pyridinum cross-link (deoxypyridinoline) were assayed by ELIZA and urinary creatinine was measured by colorimetric method and DPD/cr was calculated.
Moreover, radiological plain X-rays were done on lower spinal vertebrae, pelvis and forearm to help in the diagnosis of osteoporosis. Bone densitometry was evaluated to confirm the presence of osteoporosis.
Following the above investigations, obtained results were tabulated and analyzed statistically. The present work revealed no sex or age difference among Child groups and controls. Child-Pugh score was significantly elevated especially in Child B & C patients versus controls and Child A ones.
On the other hand, regarding serum bone minerals, serum calcium levels were significantly lower in all Child groups than in controls. Lower serum calcium levels in cirrhotic patients could have resulted from malnutrition, vitamin D deficiency or alteration of its receptor genotypes. On the contrary, ionized calcium was significantly elevated in Child C patients versus Child A & B ones. Lactic acidosis & hypoalbuminaemia recorded in Child C cirrhotic patients could be possible factors leading to elevated ionized calcium in this Child group compared to others.
In addition, ionized calcium was lower in Child A & B cases versus controls. This may be due to the fact that ionized calcium level depends on total blood calcium. The latter values were lower in Child A & B patients than in controls.
As regards gender, serum calcium levels were significantly lower in total male than female patients, especially in the Child B group. This seemed to be due to the disease severity since the total male patients’ Child score was significantly higher than the females’ score. Ionized calcium showed no observable difference between males & females.
On the other hand, there was no significant difference in serum phosphorous levels among Child groups and controls. Moreover, its change was also not significant as regard gender.
Serum magnesium levels in this study showed unremarkable changes among Child groups and controls. However, serum magnesium in Child A male patients was lower than in females. This could be explained by the fact that the disease was severer in males than in females of the same Child class. Thus, portal hypertensive gastropathy seems to lead to decreased magnesium absorption in male patients more than in females.
As regard urinary bone minerals, only urinary calcium exhibited significant differences among Child groups and controls. Its levels in Child B & C patients were significantly lower than in Child A ones. The same was observed when comparing Child C group urinary calcium with the controls’ group. Decreased urinary calcium in decompensated compared to compensated cirrhosis may be due to low blood calcium & secondary hyperparathyroidism that is found in decompensated cirrhotics. These factors increase absorption of filtered urinary calcium ,in end stage liver disease, with decrease in its urinary levels. Moreover, calcium escape into the ascitic fluid is another possible factor leading to decreased urinary calcium in end stage hepatic failure especially in Child C. However, according to patients’ gender, there was no significant difference in patients’ groups.
On the other hand, both urinary phosphorus & magnesium were significantly lower in total female patients than in males. This difference was detected between gender in Child B for urinary phosphorus & in Child C for urinary magnesium . Urinary phosphorous gender difference could be related to the change in patients’ 24 hrs urine volume output. However, their daily urinary phosphorous levels were still within normal reference range (< 1 gm/24hrs) depending on diet. Moreover, urinary magnesium difference related to sex could be also due to change in the urinary output volume and / or escape of this mineral into the extracellular fluid space in female patients more than in males. The mean Child C score in female patients was higher than in males.
Moreover, PTH levels revealed an observable change among Child groups and controls. In Child C patients, PTH was significantly higher than in Child A & B ones. Chronic hepatic cirrhosis may affect vitamin D synthesis and calcium blood level thus secondary hyperparathyroidism occurs. Moreover, defect in the role of liver in PTH cleavage and clearance may be another factor leading to elevated PTH in decompensated cirrhosis.
However, serum calcitonin values were not remarkably different among Child groups and controls. In addition, the mean DPD/cr levels rose with progression of disease severity. There was a significant difference in DPD/cr among Child groups and controls: DPD/cr of Child C group was significantly higher than that of Child A and control groups. Osteoporosis is a major complication of hepatic cirrhosis. Collagen type I molecules are present in bones & are responsible for their strength. During bone resorption these molecules breakdown & deoxypyridinoline cross-link, one of its degradation products, is released into the circulation and can be measured in serum & urine. As osteoporosis is a major event in end stage liver disease thus DPD/cr is elevated in Child C patients more than in early HCV hepatic infection and in controls.
In relation to gender, there was no significant difference between total males and females in PTH , calcitonin or DPD/cr levels. However, in Child A patients, DPD/cr was significantly lower in male patients than in female ones. The latter finding could be attributed to the fact that the peak bone mass is higher and occurs at an older age in males than in females. Thus, normal physiological decline of bone mass due to age not sex occurs in females more markedly and earlier than in males.
DEXA T and Z scores study revealed the presence of an observable difference among Child groups and controls. They were significantly lower in all Child groups than in controls. Moreover, T and Z scores in Child B & C patients were significantly lower than in Child A cases. Besides, there was no DEXA scores difference of significance between both sexes in patients’ groups. The severity of metabolic osteopathy worsen as liver functions deteriorate. Defect of liver functions per se can lead to a loss of bone mass that affects both trabecular & cortical bones. Thus, DEXA scores become lower with progression of the disease severity.
A positive correlation was detected between Child–Pugh score on one hand and each of ionized calcium, PTH and DPD/cr on the other hand. On the contrary, this score was negatively correlated with blood phosphorus & DEXA T and Z scores. Moreover, PTH had a positive correlation with both total blood calcium and its ionized form. PTH is a bone resorption hormone that leads to mobilization of calcium from bone matrix & helps in its absorption from small intestine and kidneys. Thus elevation of PTH blood levels leads to elevation of both calcium & its ionized blood levels. However, calcitonin exhibited no correlation of significance with any of the studied parameters.
In addition, DPD/cr showed a positive correlation with ionized calcium. This could be attributed to the fact that increased osteoporosis is associated with increased mobilization of calcium from bones & its ionized form to the peripheral blood. However, a negative correlation between DPD/cr with urinary calcium, phosphorus and magnesium was present. This negative correlation may be related to DPD/cr increase in decompensated cirrhosis where escape of bone minerals occurs into the ascitic fluid.
Moreover, DPD/cr correlated negatively with DEXA scores, a finding which could be related to increase in bone resorption leading to decrease in bone density and elevating excretion of collagen degradation products.
As regard serum and urinary bone minerals, total blood calcium had a positive correlation with ionized calcium. In addition, urinary calcium, phosphorus and magnesium were positively correlated with each other. The latter positive correlation could be due to kidney compensation with preservation of its blood flow, glomerular filtration rate, concentration & absorption functions. These factors affect bone minerals excretion rate.
Furthermore, DEXA scores had a positive correlation with urinary calcium. This could be attributed to the fact that decrease in DEXA scores in decompensated cirrhosis is associated with reduction of serum calcium levels. Blood calcium level decrease is due to diminution of its absorption from intestine and its escape into the extracellular fluid. Moreover, increase in its absorption from the kidneys under the effect of PTH is another factor. The end result is diminished urinary calcium levels.
According to the above findings, it could be concluded that bone loss was more marked in the lumbar spines of all Child classes, especially in the late stages of hepatitis C cirrhosis (Child B and C). Moreover, secondary hyperparathyroidism occurred in decompensated HCV cirrhotic patients. PTH was significantly elevated in Child C patients but its role in high bone turnover and bone loss in HCV cirrhotic osteoporosis remains questionable. On the other hand, it was obvious that calcitonin hormone did not play any role in hepatic osteoporosis.
Furthermore, viral hepatic cirrhosis itself seems to be a dominating factor leading to osteoporosis. Thus, in cirrhotic patients, disturbance in liver functions whether digestive (bile secretion) or non-digestive (metabolic, synthetic, detoxification) could lead to hepatic osteoporosis, however, which of these disturbances cause bone loss is still ambiguous. In addition, DPD/cr as a bone resorption marker is as useful as DEXA in evaluating hepatic osteoporosis. Finally, evaluation of bone osteopenia or osteoporosis must be performed in all cirrhotic patients and therapy must be promptly started in an attempt to block enhanced bone resorption.