Vitamin D, parathyroid hormone, and bone mineral content of lumbar spine and femur in primary biliary cirrhosis

The role of vitamin d in primary biliary cirrhosis: possible genetic and cell signaling mechanisms

Primary biliary cirrhosis (PBC) is an immune-mediated chronic inflammatory disease of the liver of unknown etiology. Vitamin D deficiency is highly prevalent in patients with PBC, and many studies have demonstrated the significant effect of calcitriol on liver cell physiology. Vitamin D has antiproliferative and antifibrotic effects on liver fibrosis. Genetic studies have provided an opportunity to determine which proteins link vitamin D to PBC pathology (e.g., the major histocompatibility complex class II molecules, the vitamin D receptor, toll-like receptors, apolipoprotein E, Nramp1, and cytotoxic T lymphocyte antigen-4). Vitamin D also exerts its effect on PBC through cell signaling mechanisms, that is, matrix metalloproteinases, prostaglandins, reactive oxygen species, and the transforming growth factor betas. In conclusion, vitamin D may have a beneficial role in the treatment of PBC. The best form of vitamin D for use in the PBC is calcitriol because it is the active form of vitamin D3 metabolite, and its receptors are present in the sinusoidal endothelial cells, Kupffer cells, and stellate cells of normal livers, as well as in the biliary cell line.

Extrahepatic manifestations of cholestatic liver diseases: pathogenesis and therapy

Pruritus, fatigue, and metabolic bone disease are frequent complications of cholestatic liver diseases, which can be quite distressing for the patient and can considerably reduce the quality of life. The molecular pathogenesis of these extrahepatic manifestations of cholestasis is poorly understood, and hypotheses to explain these symptoms are being discussed. This article provides treatment recommendations for the complications of cholestasis based on putative pathomechanisms and summarizes recent experimental and clinical data involving management options.

Extrahepatic manifestations of cholestatic liver diseases: pathogenesis and therapy

Pruritus, fatigue, and metabolic bone disease are frequent complications of cholestatic liver diseases, which can be quite distressing for the patient and can considerably reduce the quality of life. The molecular pathogenesis of these extrahepatic manifestations of cholestasis is poorly understood, and hypotheses to explain these symptoms are being discussed. This article provides treatment recommendations for the complications of cholestasis based on putative pathomechanisms and summarizes recent experimental and clinical data involving management options.

Osteoporosis in children and adolescents: etiology and management

Bone mass increases progressively during childhood, but mainly during adolescence when approximately 40% of total bone mass is accumulated. Peak bone mass is reached in late adolescence, and is a well recognised risk factor for osteoporosis later in life. Thus, increasing peak bone mass can prevent osteoporosis. The critical interpretation of bone mass measurements is a crucial factor for the diagnosis of osteopenia/osteoporosis in children and adolescents. To date, there are insufficient data to formally define osteopenia/osteoporosis in this patient group, and the guidelines used for adult patients are not applicable. In males and females aged <20 years the terminology 'low bone density for chronologic age' may be used if the Z-score is less than -2. For children and adolescents, this terminology is more appropriate than osteopenia/osteoporosis. Moreover, the T-score should not be used in children and adolescents. Many disorders, by various mechanisms, may affect the acquisition of bone mass during childhood and adolescence. Indeed, the number of disorders that have been identified as affecting bone mass in this age group is increasing as a consequence of the wide use of bone mass measurements. The increased survival of children and adolescents with chronic diseases or malignancies, as well as the use of some treatment regimens has resulted in an increase in the incidence of reduced bone mass in this age group. Experience in treating the various disorders associated with osteoporosis in childhood is limited at present. The first approach to osteoporosis management in children and adolescents should be aimed at treating the underlying disease. The use of bisphosphonates in children and adolescents with osteoporosis is increasing and their positive effect in improving bone mineral density is encouraging. Osteoporosis prevention is a key factor and it should begin in childhood. Pediatricians should have a fundamental role in the prevention of osteoporosis, suggesting strategies to achieve an optimal peak bone mass.

Distúrbios do eixo cálcio-PTH-vitamina D nas doenças hepáticas crônicas

Distúrbios no eixo cálcio-PTH-vitamina D são freqüentemente associados às doenças hepáticas crônicas (DHC). Já foi demonstrado que pacientes com DHC apresentam uma tendência à diminuição do cálcio e vitamina D, com aumento compensatório do PTH. Embora a diminuição da hidroxilação da vitamina D em 25 (OH) vitamina D fosse considerada o mecanismo principal destas alterações, estudos recentes vêm demonstrando que, mesmo nos estágios avançados de doença, o fígado ainda consegue manter níveis adequados de 25 (OH) vitamina D. Desta forma, outros fatores (ex: dieta inadequada, diminuição da exposição à luz solar) seriam os responsáveis pelas alterações no eixo cálcio-PTH-vitamina D. Além disso, o tratamento das DHC com glicocorticóides (fibrose cística) e ribavirina (Hepatite C) parece contribuir como agravante destes distúrbios. Por outro lado, parece ser a osteoporose, e não a osteomalácia ou o hiperparatireoidismo secundário, a principal alteração nas DHC. Assim, continua objeto de discussão o papel das alterações do eixo cálcio-PTH-vitamina D na osteodistrofia hepática.

Calcium-parathyroid hormone-vitamin D axis and metabolic bone disease in chronic viral liver disease

BACKGROUND

The main process involved in hepatic osteodystrophy seems to be osteoporosis, but decreased 25-hydroxylation of vitamin D might lead to osteomalacia and secondary hyperparathyroidism.

METHODS AND RESULTS

We studied bone mineral density (BMD) by using DEXA-Expert Lunar, biochemical markers of bone turnover and calcium-parathyroid hormone (PTH)-vitamin D axis in 100 patients with chronic viral hepatitis secondary to hepatitis C virus: 49 non-cirrhotic (NCir) and 51 with cirrhosis (Cir) confirmed by liver biopsy and/or clinical and biochemical features. When compared to the age-matched population, 25% of the patients had low BMD at the lumbar spine (LS), 26.2% at Ward's triangle, 15.5% at the femoral neck (FN), and 20.2% at the trochanter. No difference was found either between Cir and NCir groups or between sexes. Urinary N-telopeptide was increased in 31.86% of the patients, and negatively correlated with BMD at the LS and trochanter (P < 0.02). Serum bone-specific alkaline phosphatase was elevated in 21% of the patients and negatively correlated with BMD at the trochanter and Ward's triangle (P < 0.02). Fasting 25-hydroxyvitamin D was low in only three Cir patients, with no difference between the Cir and NCir groups, but it was higher in men (51.8 +/- 16.0 ng/mL) compared to women (40.4 +/- 14.4 ng/mL; P = 0.001). Fasting serum calcium was lower in Cir than NCir patients, P = 0.019. Fasting intact PTH was elevated in 42% of the patients, but the mean serum levels were similar in Cir and NCir groups.

CONCLUSION

We found no evidence of vitamin D deficiency, but cannot exclude the participation of PTH in the high bone turnover and bone loss in the population with chronic viral hepatitis.

Management of osteoporosis in primary biliary cirrhosis

Osteoporosis is not a significant problem in the majority of patients with primary biliary cirrhosis (PBC). However, substantial bone-related morbidity may occur in patients with advanced disease, in particular after liver transplantation. The cause of osteoporosis in PBC is multifactorial, and pathophysiological mechanisms specifically related to PBC have not been defined. In general, the principles of management followed in post-menopausal osteoporosis also apply in chronic liver disease. Dual energy X-ray absorptiometry is currently the method of choice for monitoring bone mineral density. Avoidance of conditions with potential negative effects on bone mass, and maintaining adequate serum vitamin D levels and calcium intake form the cornerstone in preventing osteoporosis. Bisphosphonates are the most logical choice when specific medical treatment of PBC-associated osteoporosis is indicated, as well as for preventing bone loss during glucocorticoid treatment and after liver transplantation. Recent studies suggest that active vitamin D analogues are effective alternatives in the post-transplant setting.