Changing osteocalcin concentrations during pregnancy and lactation: implications for maternal mineral metabolism

We measured serum osteocalcin concentrations in 82 pregnant and 21 nonpregnant women. Osteocalcin values declined in the second trimester, but returned to nonpregnant levels late in the third trimester. The mean serum osteocalcin concentration in 36 women during pregnancy (mean gestation, 26 weeks) of 2.8 ng/mL was significantly lower than that in nonpregnant women (6.4 ng/mL; P less than 0.001) or term pregnant women at delivery (6.1 ng/mL; n = 46). Serum immunoreactive PTH (iPTH) levels were significantly higher during pregnancy than in nonpregnant women [97 +/- 5 vs. 56 +/- 4 ng/L (mean +/- SE); P less than 0.001]. No significant correlations were found between maternal osteocalcin concentrations and serum phosphorus, alkaline phosphatase, or iPTH, but significant negative correlations were found between osteocalcin and total calcium or total protein. Osteocalcin concentrations in midtrimester amniotic fluid were very low (mean, 0.3 +/- 0.1 ng/mL; n = 11). In 29 lactating mothers, the mean serum osteocalcin level was 9.5 +/- 1.5 ng/mL, significantly higher than in any of the other groups (P less than 0.05), but their serum calcium and iPTH levels were normal. There was no correlation between serum osteocalcin and calcium or iPTH concentrations in lactating women. These changes are compatible with a sequence in which bone turnover is reduced during early pregnancy, rebounds in the third trimester, and increases in postpartum lactating women.     

Changes in calcium, 25(OH) vitamin D3 and other biochemical factors during pregnancy

INTRODUCTION AND AIMS: Calcium and vitamin D play major roles in calcium homeostasis and skeletal development, especially during pregnancy. This study was conducted to determine changes in calcium, 25 hydroxy [25(OH)] vitamin D3 and other biochemical factors (PTH, osteocalcin, alkaline phosphatase, magnesium, phosphorus) related to calcium homeostasis and bone turnover during pregnancy and compare the values to those of non-pregnant women. MATERIALS AND METHODS: In a cohort study, 48 pregnant women, in their first trimester of pregnancy (12+/-2.7 weeks), from 5 prenatal care centers, and 47 non-pregnant women randomly selected from the Tehran Lipid and Glucose Study (TLGS) population were enrolled. These pregnant women were followed in their second (26+/-1.9 weeks) and third trimesters (37+/-3.2 weeks) of pregnancy. Samples were drawn from June 2002 to March 2003. Including criteria were healthy women with no background of disease. Women using photo protection and calcium and vitamin D supplementation were excluded. A questionnaire was used to obtain demographic information for both groups. Venous blood samples were taken after 12-14 h of overnight fasting to measure serum calcium, phosphorus, magnesium, alkaline phosphatase, PTH, 25 (OH) vitamin D3 and serum osteocalcin levels. The repeated measures analysis of variance and t-test were used for statistical analysis. Data were matched for age and weight in both the case (in the first trimester) and control groups. RESULTS: Significant differences were found in the mean serum levels of osteocalcin and alkaline phosphatase between the three trimesters of pregnancy (p< 0.001). Osteocalcin was significantly higher in the first trimester as compared to second and third trimesters of pregnancy. Alkaline phosphatase was significantly lower in the first trimester as compared to the second and third trimesters of pregnancy and their controls. There was also a significant difference in osteocalcin in the second and third trimesters and alkaline phosphatase in the first and third trimesters of pregnancy in comparison to the control group. The mean values of osteocalcin were 12.7+/-8.5, 8.1+/-6.9, 5.6+/-5.0 and 13.9+/-7.9 ng/ml, respectively, and mean values for alkaline phosphatase were 115+/-38, 125+/-37, 174+/-61 and 134+/-35.0 Iu/l, respectively. In the first trimester, alkaline phosphatase was lower and osteocalcin was higher than in the second and third trimesters. In the first trimester of pregnancy, 20 and 40% of women had 25(OH) vitamin D3 < 10 and < 20 ng/ml, respectively, and 19% of women had serum calcium levels < 8.6 mg/dl. CONCLUSION: 60% of women in the first trimester, 48% in the second and 47% in the third trimester had either severe or moderate vitamin D deficiency. It is recommended that the importance of calcium supplements with vitamin D in pregnant women be stressed for these individuals.     

Serum osteocalcin concentrations in Paget's disease of bone

Total body scintiscans, serum alkaline phosphatase estimations, and serum osteocalcin radioimmunoassays were performed in 49 consecutive patients with Paget's disease of bone. Eleven were receiving calcitonin (salmon synthetic) at the time of the study. The serum alkaline phosphatase activities were elevated in all but one patient, with the highest value almost 50 times the upper limit of the reference range. Serum osteocalcin concentrations were elevated in 53% of patients and normal in the rest. The highest serum osteocalcin value was 4.2 times the upper limit of the reference range. The correlation coefficient between the extent of skeletal involvement and serum osteocalcin level was .70, while that between skeletal involvement and serum alkaline phosphatase level was .55. In spite of the better correlation between bone scintiscans and serum osteocalcin level, osteocalcin measurements are diagnostically less useful than serum alkaline phosphatase estimations in patients with Paget's disease of bone.     

Serum osteocalcin levels and bone alkaline phosphatase isoenzyme after oophorectomy and in primary hyperparathyroidism

Serum osteocalcin levels peaked 1 yr after oophorectomy in a prospective study of 12 women. Estrogen treatment restored serum osteocalcin to the normal range within 4 months of therapy. The changes in serum osteocalcin preceded those in bone alkaline phosphatase activity by 1-2 months, in these oophorectomized patients and during estrogen treatment. The changes in these two markers of bone formation over time were significantly different from those in urinary hydroxyproline excretion. A significant positive correlation was found between bone alkaline phosphatase and serum osteocalcin levels in patients after oophorectomy and in 18 patients with primary hyperparathyroidism. Significant positive correlations also were found between the biochemical indices of osteoblastic function and urinary hydroxyproline excretion and/or nephrogenous cAMP in primary hyperparathyroidism. In most of the patients with primary hyperparathyroidism, however, the elevation in bone alkaline phosphatase was more marked than that in osteocalcin. These data indicate that the clinical utility of serum osteocalcin as a marker of bone formation is similar but not identical to that of bone alkaline phosphatase.     

IGF-I, osteocalcin, and bone change in pregnant normotensive and pre-eclamptic women.

Pre-eclampsia is a pregnancy disorder of uncertain etiology that affects 5-10% of all pregnancies, with symptoms typically presenting around or after 20 wk gestation. We hypothesized that IGF-I, osteocalcin, and bone loss would be different among women with pre-eclampsia compared with normotensive pregnant women. There were 962 pregnant healthy women, aged 12-35, who were assessed at entry to care, at 28 wk, and at delivery for osteocalcin and IGF-I concentrations. Bone ultrasound was measured at entry to care and at 6 wk postpartum, whereas bone mineral density was measured by dual x-ray densitometry at delivery. There were 64 women (6.7%) among the women being followed who developed pre-eclampsia. In women with pre-eclampsia, IGF-I concentrations were 74% greater in the third trimester compared with the first trimester, whereas there was little change in osteocalcin concentrations. In contrast, normotensive women had an average increase of 43% in IGF-I concentrations accompanied by a 63% decline in osteocalcin concentrations. In women with pre-eclampsia, IGF-I and osteocalcin concentrations were significantly correlated (r = 0.48 and 0.43) at both the first and third trimester time points, but only in the third trimester among normotensive women (r = 0.27). The bone change difference between the two groups was not statistically significant. Women with pre-eclampsia appear to have an exaggerated IGF-I responsiveness compared with women who are normotensive; however, the strong correlation between IGF-I and osteocalcin in women with pre-eclampsia suggests that the IGF-I is able to retain its role as a local regulator of bone remodeling, as indicated by the osteocalcin concentrations.     

Sevelamer hydrochloride improves hyperphosphatemia in hemodialysis patients with low bone turnover rate and low intact parathyroid hormone levels

Sevelamer improves hyperphosphatemia without increasing the calcium load. However, it remains unknown whether sevelamer restores bone metabolism in hemodialysis patients with low bone turnover osteodystrophy and hypoparathyroidism. We investigated the changes in serum intact parathyroid hormone (iPTH) and bone metabolic marker levels after replacing calcium carbonate with sevelamer in these patients. We also conducted stratified analysis based on patient background and multivariate analysis to determine the factors affecting these parameters. During sevelamer replacement therapy, serum calcium and phosphate concentrations, and the calcium phosphate product were measured at 0, 1, 3, and 6 months. Serum iPTH, bone alkaline phosphatase and osteocalcin concentrations were measured at 0 and 6 months. In hemodialysis patients (71 men and 46 women, 63 +/- 12 years old) serum calcium levels and the calcium phosphate product decreased significantly at 1 month. Serum iPTH, bone alkaline phosphatase and osteocalcin levels increased significantly at 6 months. Increases in serum iPTH concentrations were observed in all stratified groups. Significant increases in serum bone alkaline phosphatase and osteocalcin concentrations were found only in the relative hypoparathyroidism group (iPTH levels > or =51.5 pg/mL, the median pretreatment level). Multivariate analysis showed that the factors affecting change in serum iPTH level are baseline serum iPTH, baseline calcium level (> or =9.5 mg/dL), and dialysis duration of 10 years or longer. Sevelamer appears useful for the treatment of hyperphosphatemia in these patients. Particularly, in the relative hypoparathyroidism group, the iPTH secretory response is probably enhanced and bone turnover may have been improved as a result of reducing the calcium load.     

Serum osteocalcin and total body calcium in normal pre- and postmenopausal women and postmenopausal osteoporotic patients

Serum osteocalcin was measured in 51 normal pre- and 114 postmenopausal women and in 41 postmenopausal osteoporotic patients. Total body calcium (TBCa) was determined in the same individuals by neutron activation analysis. Many of the perimenopausal nonosteoporotic women had increased serum osteocalcin values, but 15 yr or more after the menopause most of the women had serum osteocalcin levels in the normal range. Comparing normal women before and after menopause, the mean serum osteocalcin levels [7.8 +/- 4.7 (+/- SE) and 10.1 +/- 9.4 ng/mL] were not significantly different; however, the TBCa values (898 +/- 99 and 806 +/- 111 g) were significantly different (P less than 0.001). When the normal postmenopausal women were regrouped according to high vs. low osteocalcin values, TBCa and phosphorus content as well as forearm linear bone density were significantly lower in the high osteocalcin group, even though most of the other variables, including urinary hydroxyproline excretion, serum alkaline phosphatase, age, height, and weight, were not different. Osteoporotic women had a mean serum osteocalcin concentration of 17.4 +/- 8.6 ng/ml and a TBCa of 657 +/- 83 g, both significantly different from the respective values in normal and pre- and postmenopausal women (P less than 0.001 for both variables in comparison to each group). These data suggest that high serum osteocalcin levels, at least on a group basis, are an index of low skeletal mass.     

INCREASED LEVELS OF OSTEOCALCIN (SERUM BONE GLA-PROTEIN) IN RHEUMATOID ARTHRITIS

Serum osteocalcin was measured by radio-immunoassay in 56 patientswith rheumatoid arthritis (RA), and in 50 controls. Mean serum osteocalcin levels were significantly higher in patientswith RA. There was a positive correlation between osteocalcinand fasting mucopolysaccharide/creatinine ratio in both sexes,and between osteocalcin and fasting hydroxyproline/creatinineratio in women. Serum alkaline phosphatase activity, a lessspecific marker for bone formation, was also increased in RA,and there was a positive correlation with osteocalcin in bothsexes. These data suggest that overall bone turnover is increased inRA and that serum osteocalcin may provide additional informationfor the evaluation of bone metabolism in this disease. KEY WORDS: Bone, Osteocalcin, Rheumatoid arthritis     

Circulating levels of 1,25 dihydroxyvitamin D, alkaline phosphatase, hydroxyproline, and osteocalcin associated with antler growth in white-tailed deer

Alkaline phosphatase, hydroxyproline, osteocalcin, and 1,25(OH)2D were measured in biweekly serum samples obtained from 6 adult (greater than 4 years), 4 juvenile (1-4 years) and 4 fawn (less than 1 year) male white-tailed deer from Oct. 1983 to Oct. 1984. Antler length, from the pedicle to the tip, was measured at the time of serum sampling. Serum alkaline phosphatase activity and levels of hydroxyproline and osteocalcin were higher (P less than 0.05) in fawns compared with juveniles and adults reflecting increased bone metabolism in the younger deer. In adult deer serum alkaline phosphatase activity and hydroxyproline levels were elevated (P less than 0.05) during the period of antler growth, whereas serum osteocalcin and 1,25(OH)2D increased (P less than 0.05) during antler mineralization. Similar but less pronounced trends occurred in juvenile deer, possibly a reflection of skeletal growth in the younger animals. The data lend support for utilization of the deer antler cycle as a model for studies of bone disorders. Further work is needed to help clarify the role of hydroxyproline, osteocalcin, and 1,25(OH)2D in the antler cycle.     

Serum osteocalcin is increased in patients with osteomalacia: correlations with biochemical and histomorphometric findings.

The synthesis of osteocalcin or bone gla protein by osteoblasts is markedly stimulated by 1,25-(OH)2D, a key hormone in the regulation of bone mineralization. The circulating levels of osteocalcin have been shown to reflect both the osteoid matrix production and the formation rate of mineralized bone in several metabolic bone diseases (osteoporosis, thyrotoxicosis, primary hyperparathyroidism) in which both mechanisms are tightly coupled because of the absence of mineralization defect. In this study, we measured in 12 patients (7 women, 5 men, 56 +/- 15 yr old) with untreated osteomalacia serum osteocalcin and vitamin D metabolites (25OHD and 1,25-(OH)2D). The results were correlated with biochemical and histomorphometric assessment of bone remodeling. Osteomalacia was due to vitamin D deficiency (5 cases), to vitamin D malabsorption (6 cases), and to hypophosphataemia in 1 case. When compared to control values, serum osteocalcin was increased in patients with osteomalacia (7.4 +/- 4 vs. 3.7 +/- 1.3 ng/mL; P less than 0.001) and was positively correlated with serum alkaline phosphatase (r = 0.65; P = 0.03) and negatively with 25 OHD (r = -0.61; P = 0.04). Serum osteocalcin was not correlated with 1,25-(OH)2D [r = -0.45; not significant (NS)] even after exclusion of the patient with hypophosphataemia. Serum osteocalcin was positively correlated with the osteoid volume and osteoid perimeter (r = 0.71 and 0.69 respectively; P less than 0.01) but not with any of the tetracycline-based parameter of bone mineralization at the tissue level (r ranging from -0.41 to +0.42, NS). Serum 25 OHD, but not 1,25-(OH)2D, was positively correlated with the mineralization rate (r = 0.59; P less than 0.05 and r = 0.54; NS). We conclude that in patients with osteomalacia, a condition which is characterized by an increased osteoid accumulation due to a decreased mineralization rate, the increased level of serum osteocalcin reflects the increased osteoid synthesis but not the mineralization defect. In this disease, serum osteocalcin is inversely correlated to the severity of vitamin D deficiency reflected by serum 25 OHD, but not to the serum levels of 1,25-(OH)2D.     

Serum osteocalcin in Paget's disease of bone: basal concentrations and response to bisphosphonate treatment

Serum osteocalcin concentrations were measured in 42 patients with Paget's disease of bone and elevated serum alkaline phosphatase (AP) levels. High serum osteocalcin levels were found in only 22 patients. Serum osteocalcin was significantly correlated with urinary hydroxyproline excretion (r = 0.747; P less than 0.001) and, to a lesser extent, with serum AP levels (r = 0.483; P less than 0.01). In 23 patients who were followed during treatment with iv (3-amino-1-hydroxypropylidene) 1,1-bisphosphonate (APD) for 10 days, a dissociation among these 3 biochemical parameters was found. Urinary hydroxyproline excretion fell significantly (P less than 0.001), serum AP levels decreased, but not significantly, and serum osteocalcin concentrations increased progressively (P less than 0.001). This increase was greater when initial levels were lower than expected for the activity of the disease. The rise in serum osteocalcin correlated significantly with the concomitant increase in serum 1,25-dihydroxyvitamin D concentrations. Three months after initiation of treatment, all 3 parameters, urinary OHP excretion, serum AP, and serum osteocalcin levels, were near or within the normal range. These results indicate that serum osteocalcin is not a clinically useful parameter for assessment of the activity of Paget's disease. Its basal concentrations lag behind those expected from the activity of the disease, suggesting defective osteocalcin production. It appears that the functions of osteocalcin and AP as well as their initial expression by the osteoblasts are different and that this difference may be important for the quality of bone formed in Paget's disease. APD can modulate the release of osteocalcin, possibly through stimulation of 1,25-dihydroxyvitamin D production, although other factors may be involved.     

Serum osteocalcin and vitamin D metabolites in patients with ankylosing spondylitis.

OBJECTIVES--Osteocalcin is the major non-collagenous protein of bone and is regarded as a specific index of bone formation. The aim of this study was to examine the rate of bone formation measured by osteocalcin in 38 patients with ankylosing spondylitis (AS) and its dependence on various parameters of calcium and phosphate metabolism. METHODS--Serum osteocalcin, alkaline phosphatase, parathyroid hormone, and 1,25-dihydroxyvitamin D were measured in 38 patients with ankylosing spondylitis and in 52 controls. RESULTS--Mean serum osteocalcin was significantly reduced in patients with AS (men 1.7 (1.1) ng/ml; women 1.2 (1.1) ng/ml) compared with the corresponding control groups (men 3.2 (1.3) ng/ml; women 4.1 (1.7) ng/ml). In contrast, alkaline phosphatase was only slightly but significantly higher (135 (44) U/l) in patients with AS than in the corresponding controls (114 (35) U/l). Serum parathyroid hormone (AS 3.1 (0.7) v 2.7 (0.6) mE/ml) and 1,25-dihydroxyvitamin D (AS 64.0 (34.5) v 52.4 (6.7) pg/ml) were slightly but not significantly higher in patients with AS. Consequently, as both hormones are known to stimulate osteocalcin synthesis, they are not responsible for low osteocalcin levels in patients with AS. No significant correlation between alkaline phosphatase and osteocalcin was found. Low serum levels of osteocalcin in patients with AS reflect lower osteoblastic activity in AS. CONCLUSIONS--Bone turnover in patients with AS is characterised by low bone formation in the presence of normal levels of calcium regulating hormones.     

Dynamic changes in serum osteocalcin levels in the perinatal periods

Osteocalcin is a bone-specific protein released into the blood proportional to the rate of new born formation. It is widely accepted that the level of serum osteocalcin is a clinical marker of bone turnover. Nephrogenic cAMP is a specific indirect parameter of the biologically active parathyroid hormone. For analysis of bone metabolism during pregnancy, we measured the concentrations of osteocalcin and nephrogenic cAMP in the maternal serum during pregnancy and in the cord serum at delivery. Nephrogenic cAMP values (n mol/dl GF: mean +/- SEM) increased from the first trimester (1.5 +/- 0.21) to the term (2.11 +/- 0.11). Osteocalcin values (ng/ml: mean +/- S.D.) conversely declined from the first trimester (3.17 +/- 1.66) until the term (1.48 +/- 0.71) and acutely increased in the puerperium (5.91 +/- 2.58). These results might indicate that pregnancy induces a state of secondary hyperparathyroidism, but bone turnover is suppressed. In the cases of uncomplicated deliveries, the concentration of osteocalcin in the umbilical vein was significantly higher than that in the cord artery. This result suggests that a protein immunologically reactive to the osteocalcin antibody might be produced in the human placenta.     

Clinical usefulness serum int-P I NP levels as a bone formation marker in hemodialysis patients

Since intact collagen I amino-terminal propeptide (P I NP) is known to be cleared from blood via liver, its level in blood is hypothesized to be independent of renal function. Serum P I NP, in contrast to serum bone alkaline phosphatase (BAP) and intact osteocalcin (OC), did not show any significant change between before and after a hemodialysis session. Serum P I NP correlated significantly in a positive manner with the other bone formation markers, bone-specific alkaline phosphatase and osteocalcin and also with intact parathyroid hormone in the patients on hemodialysis. In summary, serum P I NP may be very useful for prediction of radius bone loss as well as other serum bone formation markers and evaluating the osteoblastic function in hemodialyzed patients.     

Biochemical markers of bone turnover during pregnancy: a longitudinal study.

OBJECTIVE: The objective of this study was to prospectively investigate the effect of pregnancy on biochemical markers of bone turnover in healthy pregnant women. METHODS: During the course of our longitudinal study, biochemical markers of bone remodeling were measured in all three trimester of pregnancy (first trimester: 12.5+/-1.8 SD, second trimester: 21.6+/-1 SD, third trimester: 34.8+/-1.6 SD weeks of gestation). Serum type I collagen C-telopeptides (CTX) and a crosslinked peptide of the carboxy-terminal telopeptide of type I collagen (ICTP) were used as markers of bone resorption. Bone alkaline phosphatase (BAP) and the N-terminal propeptides of type I collagen (PINP) were used as biochemical markers of bone formation. Blood samples for the analysis of all 4 biochemical markers according to each trimester of pregnancy were available in 49 patients. RESULTS: The main changes for all biochemical markers were seen between the second and the third trimester. According to the markers of bone resorption, both serum CTX and ICTP showed a significant increase from the first to the third and from the second to the third trimester (p<0.001; median percentage change: CTX=101.5% and ICTP=40%). Concerning markers of bone formation, PINP showed a significant decrease from the first to the second trimester (p=0.001) followed by a significant increase from the second to the third trimester (p<0.001, 63.8%) and an overall increase from the first to the third trimester (p<0.001). BAP also showed a significant increase from the second to the third trimester (p<0.001; 51.7%) and an overall increase from the first to the third trimester (p<0.001). CONCLUSION: Markers of bone resorption were significantly increased during pregnancy. In contrast to bone resorption, markers of bone formation showed an increase as well as a decrease during pregnancy indicating a state of high bone turnover. This might coincide with the change in bone mineral density that was observed in some, but not all, studies using "dual-energy x-ray absorptiometry" (DXA) as well as "quantitative ultrasonometry" (QUS).     

Serum immunoreactive erythropoietin during pregnancy and in the early postpartum

We studied 209 women during normal pregnancy, at delivery, or in the early postpartum, to determine whether erythropoietin (EPO) response was appropriate for the degree of anaemia. Serum immunoreactive EPO was measured in 74 nonpregnant women, including 33 normal subjects (16.4 +/- 4.1 mU/ml) and 41 women with hypoplastic, haemolytic, dyserythropoietic, or iron-deficient anaemia. An inverse linear relationship (R = -0.88, P less than 0.0001) between log(EPO) and Hct was observed. Predicted EPO values were derived for each Hct and an O/P ratio of observed/predicted log(EPO) was calculated for each sample (1.00 +/- 0.10, range 0.80-1.20). Serum EPO levels (mU/ml) were significantly higher during pregnancy (30 +/- 16, n = 142), at delivery (31 +/- 16, n = 41), and on day 7 postpartum (37 +/- 35, n = 26) than in normal women (P less than 0.001). EPO levels increased steadily from 18 +/- 6 mU/ml in the first, to 26 +/- 14 mU/ml in the second, and to 35 +/- 18 mU/ml in the third trimester (P less than 0.0001). The O/P ratio was normal on day 7 postpartum (1.01 +/- 0.16), at delivery (1.03 +/- 0.16), and in the third trimester (0.96 +/- 0.15), but was significantly reduced in the first two trimesters (0.88 +/- 0.15, P less than 0.001). A significant negative correlation between log(EPO) and Hct was lacking in the first two trimesters, was present but with a reduced slope during the third trimester and at delivery, and was normal postpartum. We conclude that EPO response to anaemia is impaired in early pregnancy, recovers in late pregnancy, and normalizes rapidly in the postpartum.     

Serum melatonin during human pregnancy

Serum melatonin concentrations from 55 pregnant healthy women (13 during the first, 18 during the second and 24 during the third trimester) and 11 non-pregnant control women were measured radioimmunologically at 11.00 h (Study A). In addition, serum melatonin concentrations from 12 women in early and 11 women in late pregnancy were measured every four hours throughout the day (Study B). Serum melatonin levels during the third trimester of pregnancy (76.5 +/- 38.3 pmol/l) were significantly (p less than 0.01) higher than those during the first (29.7 +/- 9.9 pmol/l) and the second trimester (39.1 +/- 11.2 pmol/l) and those of non-pregnant control women (41.7 +/- 15.5 pmol/l) and there was a positive correlation between the week of gestation and serum melatonin at 11.00 h (Study A). A clear diurnal rhythm in serum melatonin concentrations was found both in early and in late pregnancy (Study B). The amplitude and duration of the nocturnal rise of melatonin were higher during late pregnancy, but there was no clear phase shift. Increased serum concentration of melatonin in late pregnancy may be due to increased synthesis and secretion or retarded metabolism of melatonin during late pregnancy.     

Biochemical analysis of bone and mineral metabolism in liver cirrhosis

We investigated the disorder of bone and mineral metabolism in 29 patients with liver cirrhosis who were classified into two subgroups with (group 1, n = 13) or without (group 2, n = 13) osteopenia according to the method of Jikei. Serum levels of osteocalcin level, bone-type alkaline phosphatase activity and calcium concentration in serum and urine in these patients and 25 normal control subjects were determined. Serum osteocalcin level and bone-type alkaline phosphatase activity were elevated in group 1 compared with those in group 2 and normal control subjects. Serum and urine calcium levels in group 1 were similar to those in group 2. However calcium-creatinine ratio in urine was higher in group 1 than in group 2. These present observations indicate that osteopenia in patients with liver cirrhosis is due to high turnover of bone metabolism.     

SODIUM FLUORIDE STIMULATES OSTEOCALCIN IN NORMAL SUBJECTS

To test whether the administration of sodium fluoride in vivo results in an increase in osteocalcin concentration, we administered sodium fluoride to seven healthy male subjects for a period of 3 weeks. Fasting calcium, phosphate, alkaline phosphatase, 25-hydroxyvitamin D, parathyroid hormone and osteocalcin were measured prior to, during and 6 weeks after fluoride administration. Plasma calcium, phosphate and alkaline phosphatase and serum 25-hydroxyvitamin D and parathyroid hormone concentrations did not alter. Serum osteocalcin concentrations increased following fluoride administration, and the mean osteocalcin concentration at 3 weeks was significantly higher than the pretreatment mean. Plasma urea and creatinine concentrations did not alter. Six weeks after the cessation of fluoride treatment, the mean serum osteocalcin concentration had returned to the pretreatment baseline. We conclude that fluoride administration in normal subjects over a short period increases serum osteocalcin concentration and probably stimulates osteoblastic activity.     

Effects of raloxifene therapy on circulating osteoprotegerin and RANK ligand levels in post-menopausal osteoporosis

Previous in vitro studies suggest that the anti-resorptive effect of raloxifene might be mediated by changes in several cytokines involved in the bone remodeling process. In this context, the osteoprotegerin (OPG)- receptor activator of NF kappa B ligand (RANKL) system is considered a key component in the osteoclastogenesis regulation. The aim of this study was to determine the effects of raloxifene treatment on serum concentrations of OPG, receptor RANKL and its relationship with biochemical markers of bone turnover and bone mineral density (BMD) in previously untreated women with post-menopausal osteoporosis. We selected 47 post-menopausal women (mean age 63+/-7 yr) with densitometric criteria of osteoporosis. We determined at baseline, 3, 6, and 12 months anthropometric parameters, biochemical markers of bone turnover, serum levels of 25(OH) D, serum levels of OPG and RANKL. BMD (dual-energy x-ray absorptiometry) in lumbar spine (LS) femoral neck and total hip was measured at baseline and 12 months after raloxifene (60 mg/day) treatment. Serum levels of OPG decreased in the 3rd and 6th month of treatment (p<0.001) and returned to basal levels in the 12th month. There was a significant decrease of RANKL levels and OPG/RANKL ratio after 1 yr of raloxifene treatment. In addition, BMD in LS increased significantly (2.5%) in the 12th month of treatment (p=0.031). Finally, the biochemical markers of bone turnover (total alkaline phosphatase, bone alkaline phosphatase, osteocalcin, tartrate-resistant acid phosphatase, urine cross-linked carboxi-terminal telopeptide of type I collagen) decreased significantly from the 3rd month of treatment. In conclusion, our results support the hypothesis that raloxifene may inhibit osteoclast activity, at least partly modulating the OPG-RANKL system.