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Biomedical subjects

R A Cowan

Publications and source records attributed to R A Cowan.

At least 37 records · Page 2Linked to original sources
PubMed1998

Clinical variability of target volume description in conformal radiotherapy planning.

PURPOSE: The pivotal step in radiation planning is delineation of the target volume and production of a treatment plan to encompass this. This study assesses the variation of physicians in creation of these volumes. METHODS AND MATERIALS: Three radiologists and eight radiation oncologists outlined the gross tumour volume (GTV) on the planning CT scans of four cases with T3 bladder cancer. In addition, the radiation oncologists (RO) created a planning target volume according to a set protocol for all cases. Volumes were produced and comparison of these volumes and the position of the isocenters were analysed. In addition, the margins allowed were measured and compared. RESULTS: There was a maximum variation ratio (largest to smallest volume outlined) of the GTV in the four cases of 1.74 among radiologists and 3.74 among oncologists. There was a significant difference (p = 0.01) in mean GTV between RO and the radiologists. The mean GTV of the RO exceeded the radiologists by a factor of 1.29 with a mean difference of 13.4 cm3. The variation ratio in PTV among oncologists ranged from 1.25 to 3.33. There was no significant difference in mean PTV values between the two groups of ROs divided by specialization in uro-oncology. The mean variation in location of the isocenter from the centroid of the radiologists' volume in the four cases was from 2.6 to 5.7 mm. There was, however, a wide range of values from 1.4 mm to 24.1 mm. Median margin per case ranged from 14.7 to 18.7 mm. Minimum margins allowed in each case varied from minus 7 mm to 9 mm. CONCLUSION: This study demonstrates significant interphysician variability in producing target volumes and radiation plans for conformal radiotherapy. The scale of this difference is clearly of significance, with up to 3-fold variation in volumes delineated by clinicians. The factors leading to these differences will be further addressed. The existence of such variability, however, clearly needs to be accepted as a factor in the overall uncertainty analysis in conformal radiotherapy planning.

Humans↗
PubMed1998

The role of radiotherapy in the treatment of localised intermediate and high grade non-Hodgkin's lymphoma in elderly patients.

BACKGROUND AND PURPOSE: The treatment of elderly patients with high or intermediate grade non-Hodgkin's lymphoma (NHL) remains difficult and controversial. In order to audit our own practice, 270 elderly patients treated between 1988 and 1993 with this diagnosis were retrospectively reviewed. MATERIAL AND METHODS: 81 patients unfit for chemotherapy received fractionated radiotherapy for apparently localised stage I or II disease. The median age of the patients was 78 years (range 70-87 years). Forty stage I and 17 stage II patients had extra-nodal sites of disease. The radiation field included the primary site plus immediate adjacent nodes. RESULTS: After a median follow-up of 3.9 years the 5-year overall and disease-free survival rates were 33% and 31%, respectively. Age (hazard ratio (HR) 1.22, P = 0.03), stage (HR 5.50, P = 0.02) and lactate dehydrogenase level (HR 1.003, P = 0.004) were identified as independent risk factors for relapse. CONCLUSION: These factors can define a group in which radiotherapy can produce acceptable survival rates (age < or = 80 years, stage I and lactate dehydrogenase < or = 500). This group represented 34% of those patients where all these variables were recorded and had 5-year disease-free and overall survival rates of 56% and 62%, respectively.

Age Factors↗
PubMed1997

Bladder movement during radiation therapy for bladder cancer: implications for treatment planning.

PURPOSE: To describe and quantify bladder movement during radical radiation therapy (RT). To attempt to identify factors that predict for excessive alterations in bladder position. To use the above information to assist in defining the "adequate" planning target volume margin. METHODS AND MATERIALS: Thirty patients with bladder cancer suitable for radical courses of RT were followed prospectively. Patients had an initial planning computerized tomography (CT) scan of the pelvis and three subsequent scans performed weekly during the treatment period. The following measurements were made on each scan in the midbladder slice: maximum anteroposterior (AP) and lateral bladder dimensions, AP rectal diameter, and the distance (margin) between the bladder walls (anterior, posterior, right, and left lateral) and the 95% isodose line. Various patient and tumor data, including bladder and bowel symptoms, were recorded to attempt correlation with bladder movement. RESULTS: Bladder size: the median bladder size (area) over all scans in all patients was 36.9 cm2 (range: 16.2 to 80.9 cm2). The change in bladder area across each sequence varied from 3.3 to 29.1 cm2 (7-55% change in area between scans). Patients with bladders of larger than the median size on the planning scan (despite emptying) were more likely to have alteration in size than those with small bladders, and this change was in the direction of contraction (p = 0.01). Bladder displacement: bladder wall movement of > 1.5 cm was defined as "significant." Eighteen of 30 patients (60%) demonstrated "significant" movement of at least one bladder wall relative to the original isodose plot. Movement resulting in margin reduction occurred in 10 patients (33%). Two patients required treatment replanning due to consistently altered bladder position. There was no pattern to displacement through RT, and all walls were at approximately equal risk of movement. Factors influencing bladder movement: posterior bladder wall movement appeared to relate to "marked" (>2 cm) rectal diameter change. There was a trend for patients with larger amounts of residual bladder tumor (greater than the median) to exhibit more bladder movement; 11 of 14 "moved" compared with 7 of 16 patients with less residual tumor. Other clinical factors including age, sex, body size, acute RT reaction, and tumor stage did not appear to relate to bladder movement. CONCLUSION: Bladder movement during RT is clinically relevant and is random with respect to both time and direction. We recommend, at least with respect to tumor-bearing regions of the bladder, that no less than a 2.0 cm margin should be allowed.

Aged↗
PubMed1996

A comparison of the effects of alfacalcidol treatment and vitamin D2 supplementation on calcium absorption in elderly women with vertebral fractures.

Although vitamin D supplementation in the frail elderly improves calcium absorption, suppresses parathyroid hormone, decreases bone loss and reduces the risk of fractures, such treatment may be ineffective in patients with vertebral osteoporosis, because of impaired vitamin D metabolism or resistance to the action of vitamin D metabolites on the bowel. We have therefore performed a randomized, single masked study comparing the effects of alfacalcidol treatment (0.25 micrograms twice daily) and vitamin D2 supplementation (500-1000 units daily) on calcium absorption and bone turnover in 46 elderly women (median age 69 years, range 64-79 years) with radiological evidence of vertebral fractures. Serum 25-hydroxyvitamin D increased significantly after 3 and 6 months of treatment with vitamin D2 (p < 0.001), but was unchanged in the group receiving alfacalcidol. Serum 1,25-dihydroxyvitamin D did not change significantly in either group over the study period. Fractional 45Ca absorption increased after 3 months of treatment with alfacalcidol (p < 0.05), but was unchanged with vitamin D2. There was also a reduction in plasma intact parathyroid hormone and serum alkaline phosphatase after 6 months of treatment with alfacalcidol (p < 0.05) which was not seen in the group receiving vitamin D2. Our study shows that vitamin D2 supplementation is ineffective in stimulating calcium absorption in elderly women with vertebral osteoporosis. By increasing calcium absorption in such patients, alfacalcidol may prove more effective than vitamin D in the management of vertebral osteoporosis.

Absorption↗
PubMed1995

Are elderly Asians in Britain at a high risk of vitamin D deficiency and osteomalacia?

Many studies have shown the indigenous elderly population and Asian immigrants to be groups at particular risk of vitamin D deficiency and osteomalacia, but there are no data on the risks in elderly Asians. In this community-based study a group of elderly Asians was compared with control groups of elderly and young whites and young Asians. Levels of 25-hydroxyvitamin D3 (25-OHD3) were significantly lower (p < 0.0001) in elderly Asians (21/37) and young Asians (7/17) compared with white controls. The difference in parathyroid hormone (PTH) between Asians and whites was also significant (p < 0.0007) as was that between young and old (p < 0.0002). Abnormal PTH and 25-OHD3 (high PTH and low 25-OHD3), indicative of a high risk of osteomalacia, occurred in 22% of elderly Asians compared with 6% of elderly whites. The calcium, phosphate and alkaline phosphatase were normal in all individuals. Among the Asians, vegetarianism was not related to lower 25-OHD3 levels. Symptoms suggestive of osteomalacia were more common (p < 0.05) in elderly Asians than in their white counterparts. This first study of 25-OHD3 levels in community-resident elderly Asians suggests that more than half were low, placing them at a significantly higher risk of osteomalacia.

Adult↗
PubMed1994

Artificial ultraviolet whole-body radiation does not modify serum lipoprotein, plasma fibrinogen, plasminogen or antithrombin III concentrations in post-myocardial infarction patients.

The relationship of ischaemic heart disease (IHD) to seasonal and latitude variation has prompted speculation that exposure to the ultraviolet component of solar radiation may reduce IHD risk. This hypothesis was partially tested by exposing 14 post-myocardial infarction patients to a 6 week course of artificial whole-body ultraviolet radiation (UVR). Serum lipoprotein and plasma coagulation factor concentrations were measured before and after the course of UVR. Results were compared with similar measurements from a placebo-controlled group of 13 post-myocardial patients. Despite a more than two-fold rise in mean serum 25-OHD, serum lipoprotein and plasma fibrinogen, antithrombin III and plasminogen concentrations did not change significantly in the UVR group. Significant but minor change in prothrombin time and thrombin time in the placebo group appear unlikely to be of biological significance. Seasonal and latitude variation in these IHD risk factors appear unrelated to corresponding variation in solar UVR exposure.

Antithrombin III↗
PubMed1994

Acute effects of intravenous 1 alpha-hydroxycholecalciferol on parathyroid hormone, osteocalcin and calcitriol in man.

The acute effects of a single intravenous injection of 2 micrograms of 1 alpha-hydroxycholecalciferol (alfacalcidol) were studied for a 24-h period in six normal males (mean age 33 years), six women with primary hyperparathyroidism (mean age 72 years) and six women with established osteoporosis (mean age 63 years). In all three groups, serum calcitriol levels rose to a peak 2-3 h after administration of alfacalcidol. Basal levels were highest in the primary hyperparathyroidism group at (mean +/- SEM) 81 +/- 2 vs 62 +/- 12 (normal males) (p < 0.05) and 56 +/- 5 pmol/l (osteoporosis) (p < 0.01). Highest peak levels were found also in the primary hyperparathyroidism group at 150 +/- 15 vs 114 +/- 15 (normal males) (p < 0.05) and 127 +/- 15 pmol/l (osteoporosis) (p < 0.01). The rise in calcitriol was higher in the primary hyperparathyroidism group than either the normal males or osteoporotic patients (p < 0.05). No significant differences were evident in basal serum calcidiol concentrations among the three treatment groups. As might be expected, highest basal concentrations of parathyroid hormone (PTH), serum calcium and serum osteocalcin were noted in the primary hyperparathyroid group (PTH: 17.1 +/- 7.7 vs 1.9 +/- 0.5 (normal males) (p < 0.01) and 2.1 +/- 0.3 pmol/l (osteoporosis) (p < 0.01); calcium: 3.06 +/- 0.08 vs 2.50 +/- 0.02 (normal males) (p < 0.01) and 2.43 +/- 0.02 mmol/l (osteoporosis) (p < 0.01); osteocalcin: 1.10 +/- 0.08 vs 0.56 +/- 0.16 (normal males) (p < 0.05) and 0.53 +/- 0.21 nmol/l (osteoporosis) (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Association of severe haemophilia A with osteoporosis: a densitometric and biochemical study.

Following a femoral neck fracture and vertebral compression fractures in two patients with severe haemophilia A, bone density and turnover were measured in 19 males with severe haemophilia A (all HIV negative, 18/19 hepatitis C antibody positive) and in 19 age/sex matched controls. Bone density at the lumbar spine (L2-4), measured by dual energy X-ray absorptiometry, was significantly lower in the haemophiliac patients (HPs) at (mean +/- SEM) 1.109 +/- 0.042 g/cm2 vs. 1.234 +/- 0.027 in controls; p = 0.018. Femoral neck density was also lower at 0.877 +/- 0.034 g/cm2 (HPs) vs. 1.067 +/- 0.032; p < 0.0005. No significant differences were evident between the groups for serum calcium, parathyroid hormone, luteinizing hormone, follicle-stimulating hormone or 1,25 dihydroxyvitamin D3, nor for fasting urinary hydroxyproline, pyridinoline or deoxypyridinoline excretion. Serum total alkaline phosphatases was elevated in HPs at 200 +/- 10 U/l vs. 158 +/- 8; p = 0.004. Similarly, gamma-glutamyl transferase was elevated at 42 +/- 7 U/l (HPs) vs. 20 +/- 2; p = 0.007. Serum total testosterone and sex-hormone-binding globulin (SHBG) were higher in HPs at 26 +/- 2.5 nmol/l vs. 17.4 +/- 1.6 (p = 0.009) and 56 +/- 6 nmol/l vs. 27 +/- 3 (p = 0.0005), respectively. Free androgen index, however, was lower in HPs at 44 +/- 5 vs 69 +/- 7; p = 0.008. These results suggest significant osteopenia associated with haemophilia A. This may be partly due to liver dysfunction in HPs, but other factors, e.g. relative immobilization, may also be relevant.

Absorptiometry, Photon↗
PubMed1993

Recurrent cervical cancer treated with cisplatin and methotrexate.

A combination of cisplatin (80 mg/m2) and methotrexate (200 mg bolus and 400 mg as a 12-hour infusion) was given to 40 patients who developed local recurrence of cervical cancer after radiotherapy. A maximum of six courses was given at monthly intervals. Twenty-five of the forty (63%) evaluable patients responded, of which 4 (10%) responded completely. A symptomatic response, with reduction of pain, leg oedema, vaginal discharge and breathlessness was seen in 27 (68%) of patients. The median survival of all patients was 11 months. Toxicity was moderate; WHO grade 1 or greater was observed in 83% for nausea and vomiting, 67% for myelosuppression and 47% for mucositis. This combination chemotherapy is active in the treatment of recurrent cervical cancer and a modification of this regimen is currently being assessed as neo-adjuvant therapy in patients with Stage IIB-IVA cervical cancer.

Adenocarcinoma↗
PubMed1993

An evaluation of bone density and turnover in premenopausal women with type 1 diabetes mellitus.

Measurement of bone density and turnover was assessed in 20 premenopausal females with Type 1 diabetes mellitus and 27 age-sex-matched controls. Measurement was made of spinal (L2-4) and neck of femur bone density by dual-energy X-ray absorptiometry. L2-4 density was significantly higher in the diabetic patients compared with controls (1.224 +/- 0.021 g cm-2 vs. 1.161 +/- 0.020 g cm-2: p = 0.016). No significant difference was noted between the groups in neck of femur density. Measurement of bone formation was assessed by serum alkaline phosphatase and bone resorption by fasting urinary hydroxyproline/creatinine ratio. Alkaline phosphatase was significantly higher in the diabetic patients (185 +/- 16 Ul-1 vs 135 +/- 10 Ul-1: p < 0.01) as was hydroxyproline/creatinine ratio (0.028 +/- 0.003 vs 0.017 +/- 0.002: p = 0.002). No significant correlation was found between L2-4 density and glycated haemoglobin, duration of diabetes or daily dose of insulin taken. These data suggest that osteopenia is not associated with Type 1 diabetes mellitus; however these patients do have evidence of increased bone turnover and may therefore be at risk of osteoporosis in later life, particularly after the menopause.

Absorptiometry, Photon↗
PubMed1992

Factors predicting the acute effect of pamidronate on serum calcium in hypercalcemia of malignancy.

In this study we retrospectively reviewed results of the first 9 days of treatment with pamidronate at doses of 30 mg (n = 13), 45 mg (n = 9), and 90 mg (n = 13) in an attempt to see what factors influenced the response of serum calcium to pamidronate. The nadir of serum calcium obtained post treatment was correlated with pretreatment levels of nephrogenous cyclic adenosine monophosphate (NcAMP), the renal tubular threshold for phosphate reabsorption (TmPO4), and the renal tubular threshold for calcium reabsorption (TmCa). Using the post treatment serum calcium levels, patients were divided into "good" and "poor" responders depending on whether a normal serum calcium was obtained. Pretreatment NcAMP was significantly correlated with the magnitude of the response of serum calcium (r = 0.45, P = 0.0001). Pretreatment NcAMP was significantly higher in the poor responders (mean +/- SEM): 65.0 +/- 9.4 nmol/liter GF (poor responders) versus 29.6 +/- 6.3 (good responders), P = 0.004. NcAMP as a predictor of the acute response of serum calcium showed a sensitivity of 93% and a specificity of 72%. Pretreatment TmPO4 was negatively correlated with the serum calcium response post treatment (r = -0.41, P = 0.003). However, though TmPO4 tended to be lower in the poor responders, this was not statistically significant [0.65 mmol/liter GF +/- 0.09 (poor responders) versus 0.76 mmol/liter GF +/- 0.06 (good responders)]. As a predictor of the acute response of serum calcium, TmPO4 was less good with a sensitivity of 70% and specificity of 58%. No significant correlation was present between TmCa and the serum calcium response.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗
PubMed1992

Intravenous pamidronate in the treatment of osteoporosis associated with corticosteroid dependent lung disease: an open pilot study.

BACKGROUND: Bisphosphonates have been shown to be effective agents in the treatment of postmenopausal osteoporosis. Because corticosteroid associated osteoporosis is often associated with increased bone turnover, the effect of intermittent intravenous infusions of pamidronate on this condition has been investigated. METHODS: Seventeen patients (five male) with chronic corticosteroid dependent lung disease (15 asthma, two sarcoidosis) were treated with infusions of 30 mg pamidronate once every three months for one year. These patients had been taking an average of 14 (range 7.5-40) mg prednisolone a day for an average of 14 (range 3-30) years. Bone density measurements, by dual energy x ray absorptiometry, and radiography of the dorsolumbar spine were carried out before and one year after treatment. Bone formation was assessed by measurement of serum alkaline phosphatase and bone resorption by measurement of the fasting urinary hydroxyproline: creatinine ratio at the same time as densitometry and radiography were performed. RESULTS: Pretreatment density of L2-4 and the neck of the femur was significantly lower in these patients compared with a cohort of 100 age and sex matched controls (L2-4 (mean (SEM)): 0.906 (0.050) g/cm2 v 1.142 (0.016) g/cm2; neck of femur: 0.793 (0.030) g/cm2 v 0.936 (0.013)) g/cm2. After treatment there was a significant fall in serum alkaline phosphatase activity from (mean (SEM)) 220 (16) U/1 to 174 (9) U/1 (normal 80-280 U/1) and in the fasting urinary hydroxyproline:creatinine ratio from (mean (SEM) 0.040 (0.006) to 0.024 (0.003) (normal < 0.033). A significant rise was noted in L2-4 density to 0.927 (0.047) g/cm2; mean rise of 3.4%). No change was noted in density of the neck of the femur. CONCLUSIONS: Intermittent infusions of intravenous pamidronate would seem to be effective in both reducing turnover of bone and increasing bone density in corticosteroid induced osteoporosis associated with chronic lung disease. Longer term controlled studies are indicated.

Adult↗
PubMed1991

A comparison of low versus high dose pamidronate in cancer-associated hypercalcaemia.

Pamidronate has been demonstrated to be an effective agent in the treatment of cancer-associated hypercalcaemia. The dose regime, however, remains controversial. In this study 16 patients with cancer-associated hypercalcaemia were given 30 mg pamidronate by intravenous infusion and 16 were given 90 mg also by infusion. Groups were well-matched in terms of tumour types, bone metastases, pre-treatment serum calcium and creatinine, fasting urinary calcium/creatinine ratio, nephrogenous cAMP and the renal tubular threshold for phosphate reabsorption (TmPO4). The calcium lowering effect was similar in both treatment groups with nadir at day 6 of mean (+/- SEM) 2.48 mmol/l (+/- 0.06) in the 30 mg group and at day 9 in the 90 mg group of 2.51 mmol/l (+/- 0.03) (P less than 0.01). 10 patients in the 30 mg group and 8 in the 90 mg group were normocalcaemic at this point. Similarly when those patients with more severe hypercalcaemia (greater than 3.30 mmol/l, n = 7 in each group) were analysed separately, no significant difference was evident between the two groups. Urinary calcium/creatinine ratios fell to a nadir at day 6 in both groups of 0.33 (+/- 0.05) (30 mg group) and 0.37 (+/- 0.10) (90 mg group) (P less than 0.01). Follow-up results after the initial 9 days showed the mean time to relapse to be 38 days (range 18-90) in the 30 mg group and 34 days (11-105) in the 90 mg group.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium↗
PubMed1990

Low calcium dialysate and high-dose oral calcitriol in the treatment of secondary hyperparathyroidism in haemodialysis patients.

We treated nineteen haemodialysis patients with secondary hyperparathyroidism with increasing oral doses of 1,25 dihydroxycholecalciferol (calcitriol) over a 12-week period and used low calcium dialysate (1.0 mmol/l) to prevent hypercalcaemia. Nine patients received daily calcitriol and ten received calcitriol thrice weekly, and at the end of the study the mean doses were 2.0 micrograms daily and 2.6 micrograms thrice weekly respectively. The regimen was well tolerated with nine episodes of mild hypercalcaemia, none of which were symptomatic. Mean PTH and alkaline phosphatase concentrations decreased from 62.0 pmol/l (15-125) to 22.0 pmol/l(1-70) (P less than 0.01), and 144 IU/l (48-461) to 123 IU/l (61-346) (P less than 0.05) respectively. Mean serum calcium increased from 2.33 mmol/l (2.05-2.55) to 2.52 mmol/l (2.26-2.67) (P less than 0.01). There were no significant changes in serum phosphate, magnesium, or aluminium concentrations and there were no significant differences in outcome between patients receiving daily therapy compared to those receiving it thrice weekly. A combination of high-dose oral calcitriol and low calcium dialysate can reverse secondary hyperparathyroidism without causing hypercalcaemia and these results suggest a benefit over conventional low-dose calcitriol.

Administration, Oral↗
PubMed1990

Hypercalcaemia in rheumatoid arthritis revisited.

The prevalence and mechanisms of hypercalcaemia were studied in a series of patients attending a regional referral centre for rheumatic diseases. In a prospective study one case of hypercalcaemia due to primary hyperparathyroidism was found in 251 consecutive patients who were screened over a three month period. In a retrospective study of 39 patients who had been discovered to be hypercalcaemic during the preceding 12 months known cases of hypercalcaemia were found in 38 (97%) cases. Primary hyperparathyroidism was the most common cause (n = 24; 62%), followed by thiazide treatment in five (13%), cancer in three (8%), immobility in three (8%), vitamin D toxicity in two (5%), and chronic liver disease in one (3%). In one case the diagnosis remained unclear after full investigation. This study shows that the causes of hypercalcaemia in rheumatological patients are similar to those in the general population. These observations contrast with previous reports, which suggested that hypercalcaemia may be a complication of rheumatoid arthritis itself.

Adult↗
PubMed1989

Comparison of three intravenous bisphosphonates in cancer-associated hypercalcaemia.

Three intravenous bisphosphonates were compared in the treatment of cancer-associated hypercalcaemia. 48 patients were randomly allocated to one of three treatment groups (each with 16 subjects)--30 mg pamidronate or 600 mg clodronate, both as single intravenous infusions; or etidronate as three infusions of 7.5 mg/kg per day for three consecutive days. Patients were rehydrated with normal saline before bisphosphonate treatment. All three bisphosphonates lowered serum calcium by inhibiting bone resorption; pamidronate was the most potent in this respect. By comparison with the other groups, more patients in the pamidronate group became normocalcaemic, and the effect on serum calcium was apparent sooner and lasted longer.

Administration, Oral↗
PubMed1989

Contrasting mechanisms of hypercalcemia in patients with early and advanced humoral hypercalcemia of malignancy.

The mechanisms of hypercalcemia were assessed in 15 patients with humoral hypercalcemia of malignancy (HHM) who had tumors at various stages of progression. In patients with early tumors, bone biopsies were generally normal and the hypercalcemia was due to an elevation in renal tubular resorption of calcium. Conversely, osteoclastic resorption was markedly increased in patients with advanced tumors, particularly those in whom the biopsies were obtained postmortem. Osteoclast surface (Oc.S) correlated positively with the stage of tumor progression (r = 0.80, p less than 0.002), degree of immobility (r = 0.87, p less than 0.002), and level of urinary cyclic AMP excretion (r = 0.60, p less than 0.02). When compared with a group of ambulant patients with primary hyperparathyroidism (HPT), osteoblast surface (Ob.S%) in HHM was depressed (median and range): 1.2% (0-11.6%) versus 5.3% (1.1-32.0%) (p less than 0.001). However, a relatively low Ob.S (4%) and raised Oc.S (43.5%) were also seen in an immobilized patient with severe HPT. These data suggest that the PTH-related peptides currently invoked in the pathogenesis of HHM may initially cause hypercalcemia by enhancing renal tubular calcium resorption. The increase in osteoclastic activity and depression of osteoblastic activity that subsequently occurs is probably due to the combined effects of immobilization and higher circulating levels of PTHrP on the skeleton. However, the release of other bone-resorbing factors by the tumor, which have a depressant effect on osteoblastic activity, remains possible.

Adult↗