Urinary VMA, dopamine and the likelihood of neuroblastoma: a preferred way of reporting laboratory results?

Background: Neuroblastoma patients may be classified as normal or abnormal depending on reference interval and decision points for urine catecholamine metabolites. We therefore evaluated the utility of positive likelihood ratios (LR+) based on data from patients in whom the diagnosis was suspected.

Methods: Urine samples from 249 patients (122 male, 127 female) suspected of neuroblastoma were assayed for VMA by spectrophotometry and dopamine by HPLC. Ratios of VMA to creatinine (VMA/Cr) and dopamine to creatinine (DA/Cr) were calculated and age-related median scores derived relative to patients without neuroblastoma. Receiver operator characteristic (ROC) curve analysis was undertaken for the ability of median scores to identify neuroblastoma.

Results: Of the 249 patients, there were 20 confirmed cases of neuroblastoma, with ages ranging from 0 (congenital tumour) to 8.4 years. From ROC curves, VMA/Cr was found to have an area under the curve 0.96 (95% confidence interval [CI] 0.92-0.98) compared with 0.72 (95% CI 0.66-0.77) for DA/Cr, P=0.001. At the optimal decision point for VMA/Cr, LR+ was 7.2, identifying cases with a sensitivity of 95% and a specificity of 86%, and comparing favourably with published intervals.

Conclusions: VMA/Cr is more accurate than DA/Cr for the diagnosis of neuroblastoma. Reporting LR+ may also be more informative than using reference intervals and decision points.

Removal of body surface area normalisation improves raw-measured glomerular filtration rate estimation by the Chronic Kidney Disease Epidemiology Collaboration equation and drug dosing in the obese

BACKGROUND/AIM

We aimed to compared estimated glomerular filtration rate (eGFR) according to the Chronic Kidney Disease Epidemiology Collaboration equation (CKD-EPI), with (mL/min/1.73 m(2) ) and without body surface area (BSA) normalisation (CKD-EPI_noBSA, mL/min) against measured (99m) Technetium - diethylenepentaacetic acid (Tc-DTPA GFR) (mL/min) in 222 individuals, including 80 with malignancy.

METHODS

BSA was calculated for each individual using the Du Bois equation. The CKD-EPI and CKD-EPI_noBSA equations were compared with measured Tc-DTPA GFR with respect to bias, proportion within 30% of GFR (P30) and root mean square error for predicting levels of GFR, and concordance in relation to carboplatin dosing.

RESULTS

The mean (SD) for BSA and measured GFR for the entire group was 1.99 (0.25) m(2) and 127 (41) mL/min respectively. The P30 for Tc-DTPA GFR was significantly higher with the CKD-EPI_noBSA (80%) than with the CKD-EPI equation (63%, P = 0.0001). In those with body mass index (BMI) > 30 kg/m(2) , the P30 values for the CKD-EPI_noBSA and CKD-EPI were 74% and 42% respectively (P < 0.0001). Carboplatin dosing concordance for the cancer patients using the CKD-EPI and CKD-EPI_noBSA equation was 71% and 56% respectively (P = 0.07). In 78 individuals with BMI > 30 kg/m(2) , concordance in relation to carboplatin dosing using CKD-EPI_noBSA was 65% compared with 26% with the CKD-EPI (P < 0.0001).

CONCLUSION

The CKD-EPI without normalisation (CKD-EPI_noBSA) equation was superior to the CKD-EPI equation in estimating raw-measured Tc-DTPA GFR (mL/min).

Lean mass modulates glomerular filtration rate in males of normal and extreme body composition

BACKGROUND

Understanding determinants of glomerular filtration rate (GFR) is important in aiding prediction and interpretation of kidney function. Body composition is known to affect GFR but is not included in current screening of kidney disease. We investigated the association between GFR and body composition in healthy young men with differing body mass but without known diabetes or kidney injury.

METHODS

Three groups were recruited: normal BMI (n = 22) with a body mass index (BMI) <25 kg/m(2) , muscular (n = 23) with BMI ≥30 kg/m(2) and bioelectrical impedance body fat ≤20% and obese (n = 22) with BMI ≥30 kg/m(2) and bioelectrical impedance body fat ≥30%. Dietary analyses, GFR clearance by (99m) Tc-DTPA, urine protein and body composition by dual-energy X-ray absorptiometry were measured in all participants. Linear and nonlinear associations of constituents of body composition with GFR were assessed.

RESULTS

Muscular men had a higher GFR (mean 186.4 mL/min; 95% CI 171.7-201.1) than normal BMI and obese groups (P = 0.0007). Urine protein and albumin excretion were not elevated in any participants. On multiple regression analysis (r(2) = 0.60), the variables with strong associations with GFR were age (P = 0.0009) and lean mass (P = 0.0001). Fat mass, protein intake and smoking status were not associated. Skeletal muscle mass correlated significantly with GFR in all subgroups.

CONCLUSION

Age and lean mass were strong determinants of GFR. Estimates of GFR should therefore be indexed to an estimate of lean mass.

Novel inactivating mutation of the calcium-sensing receptor in a young woman with mild hypercalcaemia

A young woman with mild hypercalcaemia and an inappropriately normal serum parathyroid hormone had parathyroid scintigraphy suggestive of an active ectopic parathyroid tissue in the superior mediastinum. Urinary calcium to creatinine clearance ratio was low, and a subsequent genetic analysis confirmed a novel mutation (Q164K) in the calcium sensing receptor gene, consistent with familial hypocalciuric hypercalcaemia. We propose that this mutation accounts for her clinical and investigational findings, although a double pathology of Q164K and an ectopic parathyroid adenoma is also conceivable.

Comparison of cardiac TnI outliers using a contemporary and a high-sensitivity assay on the Abbott Architect platform

BACKGROUND

Assays for cardiac troponin (cTn) have undergone improvements in sensitivity and precision in recent years. Increased rates of outliers, however, have been reported on various cTn platforms, typically giving irreproducible, falsely higher results. We aimed to evaluate the outlier rate occurring in patients with elevated cTnI using a contemporary and high-sensitivity assay.

METHODS

All patients with elevated cTnI (up to 300 ng/L) performed over a 21-month period were assayed in duplicate. A contemporary assay (Abbott STAT Troponin-I) was used for the first part of the study and subsequently a high-sensitivity assay (Abbott STAT High-Sensitive Troponin-I) was used. Outliers exceeded a calculated critical difference (CD) (CD = z × √2 × SDAnalytical) where z = 3.5 (for probability of 0.0005) and critical outliers also were on a different side of the decision level.

RESULTS

The respective outlier and critical outlier rates were 0.22% and 0.10% for the contemporary assay (n = 4009) and 0.18% and 0.13% for the high-sensitivity assay (n = 3878). There was no significant reduction in outlier rate between the two assays (χ(2) = 0.034, P = 0.854). Fifty-six percent of outliers occurred in samples where cTn was an 'add-on' test (and was stored and refrigerated prior to assay).

CONCLUSION

Despite recent improvements in cTn methods, outliers (including critical outliers) still occur at a low rate in both a contemporary and high-sensitivity cTnI assay. Laboratory and clinical staff should be aware of this potential analytical error, particularly in samples with suboptimal sample handling such as add-on tests.

Comparison of BD Vacutainer® Rapid Serum Tube and plasma for haemolysis markers in the emergency department

Background

In recent years, a rapid-clotting serum tube, BD Vacutainer® Rapid Serum Tube (RST™), was introduced to improve turn-around times for serum samples. Previous studies reported reduced concentrations of some markers of haemolysis in RST specimens compared to other serum or plasma samples. We aimed to compare RST to plasma tubes for haemolysis markers in an emergency department (ED) setting, where increased rates of haemolysis are commonly seen.

Methods

Patients presenting to ED over an eight-day period had an RST, BD Vacutainer® PST™ II (plasma) Tube and BD Vacutainer® Heparin (non-gel, plasma) Tube collected. Blood was drawn from an intravenous cannula, and samples were promptly analysed for haemolysis index, potassium, phosphate, aspartate aminotrasferase (AST), magnesium and lactate dehydrogenase (LD).

Results

A total of 347 patient samples were included, and 9.2% of the PST samples were haemolysed. The RST tubes had small increases in all of the haemolysis markers compared to both plasma tubes ( P ≤ 0.005), except LD which was lower in the RST group. There were no significant differences in the proportion of results above the upper reference limit between the tubes, except for LD which had a lower proportion in RST samples ( P ≤ 0.002).

Conclusion

Compared to plasma, RST specimens show small increases in several haemolysis markers, consistent with known differences between serum and plasma, but the proportion of elevated haemolysis markers is similar to plasma. In a setting with a high haemolysis rate such as ED, RST specimens provide a non-inferior sample type for markers of haemolysis.

The performances of the Cockcroft-Gault, modification of diet in renal disease study and chronic kidney disease epidemiology collaboration equations in predicting gentamicin clearance

BACKGROUND

It is unclear which renal function equation, employing an isotope dilution mass spectrometry (IDMS)-aligned creatinine assay, best predicts gentamicin clearance.

METHODS

The performances of the Cockcroft-Gault, Modification of Diet in Renal Disease (MDRD) Study and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations for predicting gentamicin clearances were assessed retrospectively in 240 patients treated with gentamicin during 2011-2012, when the local creatinine assay was IDMS-aligned. Comparisons were based on the percentage within 30% of gentamicin clearance (P 30) and the root-mean-square error (RMSE) of each equation. Gentamicin clearance was calculated from plasma concentrations using a one-compartment model.

RESULTS

The Cockcroft-Gault equation and the CKD-EPI equation corrected for individual body surface area (BSA) were associated with the highest P 30 (69% and 67%, respectively) and lowest RMSE (39 and 36 mL/min, respectively) in the 240 patients. Correction for individual BSA improved the performances of the MDRD Study and CKD-EPI equations in patients with body mass indices <18.5 or ≥30 kg/m(2). The equations systematically underestimated gentamicin clearance as gentamicin clearance increased, with performance being inferior with gentamicin clearance ≥90 versus <90 mL/min.

CONCLUSIONS

The CKD-EPI equation corrected for individual BSA, and the Cockcroft-Gault equation, provided the best estimates of gentamicin clearance. The CKD-EPI and MDRD Study equations should be corrected for individual BSA at the extremes of body size, if used for guiding gentamicin therapy. The performances of the equations were inferior in patients with higher values of gentamicin clearance.

Effect of vitamin D3 supplementation on Staphylococcus aureus nasal carriage: a randomized, double-blind, placebo-controlled trial in healthy adults

Observational studies have reported an inverse association between serum 25-hydroxyvitamin D (25OHD) concentrations and Staphylococcus aureus nasal carriage; however, clinical trials of vitamin D supplementation are lacking. To assess the effect of vitamin D3 supplementation on persistent S. aureus nasal carriage we conducted a randomized, double-blind, placebo-controlled trial among 322 healthy adults. Participants were given an oral dose of either 200 000 IU vitamin D3 for each of 2 months, followed by 100 000 IU monthly or placebo in an identical dosing regimen, for a total of 18 months. Nasal swabs for S. aureus culture and serum for 25OHD measurement were obtained at baseline, 6, 12 and 18 months of study. The mean baseline concentration of 25OHD was 72 nM (SD 22 nM). Vitamin D3 supplementation increased 25OHD levels which were maintained at >120 nM throughout the study. Nasal colonization by S. aureus was found in 31% of participants at baseline. Persistent carriage, defined as those that had positive S. aureus nasal cultures for all post-baseline swabs, occurred in 20% of the participants but vitamin D3 supplementation was not associated with a reduction in persistent carriage (OR = 1.39, 95% CI 0.63-3.06). Risk factor analysis showed that only gender was significantly associated with carriage, where women were less likely to be carriers than men (relative risk 0.83, 95% CI 0.54-0.99). Serum 25OHD concentrations were not associated with the risk of carriage. In conclusion, monthly administration of 100 000 IU of vitamin D3 did not reduce persistent S. aureus nasal carriage.

What is the best predictor of the atherogenic LDL subclass phenotype 'pattern B' in patients with type 2 diabetes mellitus?

BACKGROUND

The atherogenic lipoprotein phenotype 'pattern B' comprises a predominance of small-dense low-density lipoprotein (sdLDL). Gradient gel electrophoresis (GGE) is considered a 'gold standard' method for identifying this phenotype, but is impractical for routine laboratory use. The low-density lipoprotein cholesterol:apolipoprotein-B (LDL-C:Apo-B) ratio has been advocated as a surrogate marker for sdLDL and a direct assay for sdLDL has recently become available. We compared the sdLDL assay and LDL-C:Apo-B with more established lipid parameters to predict the presence of 'pattern B' phenotype.

METHOD

Blood was collected from 97 fasted subjects on three separate occasions. Total cholesterol, triglyceride, Apo-B and sdLDL were measured; LDL- and HDL-cholesterol were determined after ultracentrifugation. The predominant LDL particle size and phenotype were assigned by GGE.

RESULTS

'Pattern B' phenotype was identified in 36% of samples. Peak particle size showed a positive correlation with HDL-cholesterol and a negative correlation with triglyceride and Apo-B. Receiver operating curve (ROC) analysis showed triglyceride:HDL-C ratio and triglyceride alone to be the best predictors of 'pattern B' phenotype, with area under the curve (AUC) being 0.87 and 0.84, respectively. AUCs for sdLDL (0.74) and LDL-C:Apo-B (0.71) were significantly lower (P < 0.05). A high sdLDL concentration had the greatest specificity (95%) and positive predictive value (74%) for 'pattern B' phenotype, but low sensitivity (43%).

CONCLUSION

Direct measurement of sdLDL provided the most specific predictor of 'pattern B' phenotype, whereas triglyceride:HDL-C ratio or triglycerides alone, parameters readily available in most laboratories, were the best predictors by ROC analysis.

Three cases of congenital adrenal hypoplasia with novel mutations in the (NROB1) DAX-1 gene

Abnormalities in the DAX-1 gene (dosage-sensitive sex reversal-adrenal hypoplasia gene on the X chromosome) are a well-recognized cause of congenital adrenal hypoplasia. DAX-1 is expressed in the adrenal cortex, gonads, hypothalamus and anterior pituitary, which gives rise to the clinical features of this deletion. Presentations are varied but salt-wasting and/or hypoglycaemia are the most common in an infant, with late onset of hypogonadotrophic hypogonadism. Over 80 different mutations in this gene have been identified. We present three unrelated cases with variable clinical presentations, all with novel mutations in the DAX-1 gene.

Pseudo-hypertriglyceridaemia: a measurement artefact due to glycerol kinase deficiency

A man presented with elevated plasma triglycerides and was commenced on fibrate treatment. The triglycerides did not fall and compliance was questioned. The triglyceride elevation was inconsistent with the observed lack of turbidity in the plasma sample. Triglyceride elevation was not confirmed by a different analytical method and lipoprotein electrophoresis showed a normal very low density lipoprotein (VLDL) band pattern. Glycerol kinase deficiency was suspected and was supported by elevated urine glycerol, and confirmed by reduced leucocyte enzyme activity and mutational analysis of the GK gene which showed a novel three base pair deletion. Demonstration of a point mutation also excludes a contiguous gene deletion syndrome.

Uncertainty of sweat chloride testing: does the right hand know what the left hand is doing?

Although analytical variation in sweat electrolyte testing can be easily estimated, there is limited data on total variation. This study aims to evaluate the total variation of the sweat test by measuring the difference between sweat electrolyte values in specimens obtained simultaneously from two sites. Chloride is recommended in published guidelines as the only discriminant for the diagnosis of cystic fibrosis, and sodium may be measured as a guide to the adequacy of collection and analysis. Both are reported here. Sweat was collected in patients by the Gibson Cooke method from two sites simultaneously. Coefficient of variation in this laboratory is 4.1 and 5% for chloride and sodium, respectively. 295 patients had sufficient sweat collected from both sites for analysis. The values for chloride and sodium were compared between the two sites. The total coefficient of variation (CVt) calculated for the whole group between the two sites was 20.2% for chloride and 16.9% for sodium, and the standard deviations 4.3 mmol/L and 4.8 mmol/L, respectively. In patients with intermediate chloride concentrations; in different age groups; and when those tests with a difference between sodium and chloride concentration of more than 15 were excluded, minimal differences in these figures were observed. Use of strictly defined cut-off points to discriminate between normal and intermediate electrolyte values, and between intermediate and raised electrolyte values, does not reflect the variation in sweat electrolyte content found within an individual patient. This has important implications for reporting.

Quartz renal calculi: were we being led up the garden path?

Quartz stones are often considered to be of non-human origin or factitious, although in some cases, they may have a biological aetiology. X-ray diffraction (XRD) spectroscopy was used to analyse fragmented renal stones from a 61-year-old lady who presented with bilateral nephrocalcinosis. Analysis of the calculi from the left kidney showed a mixed composition: 50% calcium oxalate monohydrate and 50% quartz. This case highlights the usefulness of XRD in the differentiation of authentic from possibly factitious renal calculi.

Thyroid hormone resistance: the role of mutational analysis

The finding of increased thyroxine (T4) and tri-iodothyronine (T3) levels in a patient with normal or increased thyroid-stimulating hormone is unexpected and presents a differential diagnosis between a thyroid-stimulating hormone-secreting pituitary adenoma, generalized resistance to thyroid hormone (RTH) and laboratory artefact. Without careful clinical and biochemical evaluation, errors may occur in patient diagnosis and treatment. In the case of RTH, mutation of the thyroid hormone receptor beta gene results in generalized tissue resistance to thyroid hormone. As the pituitary gland shares in this tissue resistance, euthyroidism with a normal thyroid-stimulating hormone is usually maintained by increased thyroid hormones. To date, we have identified eight pedigrees in New Zealand with mutations in the thyroid hormone receptor beta gene, including two novel mutations. Mutational analysis of the thyroid hormone receptor beta gene allows definitive diagnosis of RTH, potentially avoiding the need for protracted and expensive pituitary function testing and imaging. Mutational analysis also enables family screening and may help to avoid potential misdiagnosis and inappropriate treatment.

Thiopurine methyltransferase and 6-thioguanine nucleotide measurement: early experience of use in clinical practice

BACKGROUND

Azathioprine and 6-mercaptopurine (6-MP) are well established for the treatment of inflammatory bowel disease (IBD). Assessing thiopurine methyltransferase (TPMT) status has been recommended to reduce the risk of serious toxicity. Measuring red blood cell (RBC) 6-thioguanine nucleotide (6-TGN) concentrations has been recommended for dose adjustment.

AIM

To describe the results of measuring TPMT activity and genotype, and 6-TGN concentration in New Zealand.

METHODS

Canterbury Health Laboratories provided these analyses for New Zealand. Those with low TPMT activity also underwent genotyping. All results were collated and analysed descriptively. 6-TGN concentrations were correlated with the dose of thiopurine when known.

RESULTS

TPMT enzyme activity (range 1-22 U/mL) from 574 patients showed a trimodal distribution. Genotyping results matched this distribution with only mild overlap between (*1/*1) homozygote and (*1/*3) heterozygote groups. One patient without TPMT measurement before therapy had life-threatening neutropenia and was later found to have (*3/*3) genotype. TPMT analysis probably prevented two further such cases. Of 884 6-TGN concentrations (range 0-1434 pmol/10(8) RBC), 41, 39 and 20% were within, below, and above the therapeutic range of 235-450 pmol/10(8) RBC, respectively. Leucopenia was seen in some patients with high 6-TGN. 6-MMP concentrations in 177 patients with low 6-TGN suggested non-compliance in 31, underdosing in 130, and preferential metabolism of 6-MP to 6-methylmercaptopurine in 16. There was poor correlation between azathioprine dose and 6-TGN concentration (r(2) = 0.002), supporting 6-TGN monitoring.

CONCLUSIONS

Measurement of TPMT enzyme activity and 6-TGN concentration has been well-integrated into clinical practice. These tests should reduce the risk of toxicity and improve efficacy with thiopurines in patients with IBD.

Circulating levels of isoflavones and markers of 5alpha-reductase activity are higher in Japanese compared with New Zealand males: what is the role of circulating steroids in prostate disease?

Epidemiological evidence implicates dietary isoflavone intake as protective against prostate disease. A putative mechanism is attenuated circulating androgen levels in male populations consuming an isoflavone rich diet. We investigated this hypothesis by collecting plasma from 60 Japanese and 60 New Zealand males aged between 21 and 31 years each consuming their traditional diets. We measured plasma testosterone, dihydrotestosterone (DHT), androstenedione, dehydroepiandrosterone sulfate (DHEAS), the combined levels of androsterone sulfate and epiandrosterone sulfate (AoS/epiAoS), sex hormone-binding globulin, and cortisol and corticosteroid-binding globulin as well as the isoflavones genistein and equol. Plasma genistein and equol levels were several times higher in Japanese males as would be expected from an isoflavone rich diet. However, androstenedione, DHEAS, calculated free testosterone and paradoxically markers of 5alpha-reductase, DHT and AoS/epiAoS were all also significantly higher in Japanese rather than the New Zealand male counterparts. All other comparisons were not significant. Plasma DHT and DHEAS correlated positively with plasma equol and plasma AoS/epiAoS correlated positively with genistein levels. Taken together the results suggest that, rather than reduced levels of steroidogenesis, Japanese males may have increased 5alpha-reductase activity and possibly altered 17beta OH steroid dehydrogenase activity. Significantly the positive association between isoflavones levels and 5alpha-steroids is counter-intuitive to isoflavone intake offering prostate protection, unless this is postulated to occur through other mechanisms.

The postprandial state does not impair endothelial function in women with type 2 diabetes irrespective of glycaemic control

AIMS/HYPOTHESIS

The postprandial state has been shown to be associated with endothelial dysfunction, a predictor of cardiovascular morbidity. In type 2 diabetes, postprandial metabolic excursions are prolonged and exaggerated, but less pronounced if glycaemic control is optimised. We investigated the impact of improved glycaemic control on endothelial function in the postprandial state.

METHODS

We studied 19 postmenopausal women with type 2 diabetes and ten non-diabetic subjects. Participants with diabetes were re-studied 3 months after intensive glucose regulation. We measured forearm blood flow by strain gauge plethysmography during rest, during acetylcholine infusion and post ischaemia in the fasting state, and again 3 hours after a mixed meal (660 kcal, 55% fat).

RESULTS

Endothelium-dependent vasodilation was impaired in the diabetic group (p<0.005) and improved following an HbA1c reduction of 0.96% (p<0.05 for high-dose acetylcholine infusion). Postprandial metabolic excursions were higher in the diabetic group (p<0.001, p<0.01 and p<0.05 for glucose, insulin and triglycerides respectively). Resting forearm blood flow increased in all groups after the meal (p<0.005). There was no difference in fasting and postprandial endothelium-dependent vasodilation before and after improved glucose regulation in either group.

CONCLUSIONS/INTERPRETATION

The postprandial state does not impair endothelial function in non-diabetic women and does not make pre-existing endothelial dysfunction worse in women with type 2 diabetes, irrespective of glycaemic control.

Variegate porphyria presenting with acute autonomic dysfunction, intussusception and renal infarction

A 48-year-old man presented with abdominal pain, constipation and irritability one month after starting phenytoin treatment for a generalized seizure. He was hypertensive, tachycardic (BP 174/98, heart rate (HR) 100 bpm supine) and hypovolaemic. Abdominal CT demonstrated transient jejunal intussusception and infarction of the left kidney. Urinary porphobilinogen levels were increased and genetic analysis confirmed the diagnosis of variegate porphyria. Because of ongoing postural hypotension, the patient underwent further autonomic investigations. Levels of blood pressure (MBP), HR and muscle sympathetic activity (MSNA) were increased during the acute attack compared to recovery (131 versus 105 mmHg, 100 versus 60 bpm, 88 versus 26 bursts min(-1)). HR and MSNA did not increase during phase II Valsalva, whereas stroke volume (SV) decays were exaggerated (deltaMBP-56 versus 0-31 mmHg and SV 25% versus 40% baseline). Baroreflex failure causing increased sympathetic activity, decreased sympathetic and parasympathetic rapid responses, loss of splanchnic capacitance and renal salt wasting were the likely mechanisms for postural hypotension. Increased sympathetic activity may also have caused intussusception and focal renal vasoconstriction, both of which may be underdiagnosed causes of abdominal pain in acute porphyria.

Haemoglobin Marseille-Long Island and interpretation of HbA1c: which HbA1c result is the "right answer"?

A woman was screened for diabetes using glycated haemoglobin (HbA1c). Vastly different results were obtained by high performance liquid chromatography (45%), immunoassay (2.9%), and affinity chromatography (4.2%) compared with the non-diabetic range of less than 6.4%. Mass spectral studies confirmed the presence a haemoglobin variant, haemoglobin Marseille-Long Island which had confounded interpretation by all methods.

Cause-specific and total mortality in the Canterbury (New Zealand) insulin-treated Diabetic Registry population: a 15-year follow-up study

AIMS

To establish all-cause and cause-specific death rates, and risk factors for mortality in insulin-treated diabetic individuals living in the province of Canterbury, New Zealand.

METHODS

Insulin-treated diabetic subjects (n = 995) on the Canterbury Diabetes Registry were followed up over 15 years and vital status determined. Death rates were standardized and hazard regression was used to model the effects of demographic covariates on relative survival time.

RESULTS

There were 419 deaths in 11 226.3 person-years of follow-up with a standardized mortality ratio (SMR) of 2.0 (95% confidence interval (CI) 1.8-2.2). Relative mortality was greatest for the group aged 0-29 years (SMR 3.0 (95% CI 2.4-3.7)). After controlling for diabetes duration and gender, a 10-year increment in age of onset was associated with a 33% decrease in relative hazard (95% CI 29-36%), indicating that excess mortality due to diabetes declines with rising age of onset. After controlling for age of onset and gender, each 10-year increment in duration of diabetes is associated with a 26% decrease in relative hazard (95% CI 24-29%), indicating that with longer survival the mortality hazard approaches the general population hazard. Relative mortalities were increased for cardiovascular, renal and respiratory disease, but not malignancy. Relative mortality from acute metabolic complications was increased in the subgroup with age of onset of diabetes < 30 years and requiring insulin within 1 year of diagnosis.

CONCLUSIONS

Mortality rates are high for insulin-treated diabetic individuals relative to the general population.

Macro-alkaline phosphatase due to IgG kappa complex: demonstration with polyethylene glycol precipitation and immunofixation

An otherwise unexplained, persistently elevated plasma alkaline phosphatase concentration in a 71-year-old woman was found to be attributable to the presence of macro-alkaline phosphatase using polyethylene glycol precipitation. Gel filtration showed two high MW peaks with masses of about 330 kDa and 560 kDa. The alkaline phosphatase (ALP) complex was characterized by immunoelectrophoresis as a complex with IgG with kappa light chains.

A comparison of post-prandial changes in flow-mediated dilatation in patients with type 2 diabetes with and without macroalbuminuria

During the post-prandial period there is a decrease in systemic vascular resistance. This study compared meal-induced changes in flow-mediated dilatation (FMD) in patients with Type 2 diabetes with and without evidence of diabetic nephropathy as defined by the presence of macroalbuminuria. The effects on FMD of other factors such as smoking history, antihypertensive treatment and insulin use were also examined. Twelve patients with macroalbuminuria (>300 mg albumin/day) and 12 age- and sex-matched patients with normoalbuminuria (<50 mg albumin/day) participated in the study. Following a 12-hr overnight fast, forearm basal and reactive hyperaemic blood flow was assessed by venous occlusion plethysmography before and 2-hr after ingestion of a meal (2750 kJ) consisting of 56% fat, 26% carbohydrate and 16% protein. Plasma lipid and glycaemic indices were measured at the same times. The combined and grouped data was analysed using paired t tests and correlation and regression analyses. The meal resulted in significant increases in plasma glucose and triglyceride concentrations. While the meal resulted in a similar increase in basal blood flow rate in both patient groups, post-meal reactive hyperaemic flow increased significantly (p=0.04) in normoalbuminuric patients (mean individual increase: 33%) but remained unchanged in patients with macroalbuminuria (mean individual increase: 4%). The use of antihypertensive agents and insulin was also associated with an attenuated post-prandial hyperaemic response. In summary, our study demonstrated that the degree of renal impairment in patients with Type 2 diabetes may influence vasoactivity following a meal. Patients with evidence of diabetic nephropathy had a decreased post-prandial hyperaemic response, a result that indicated a reduced vasodilator reserve. The mechanism of this reduction in vasodilatation of peripheral vessels during the post-prandial period is probably multifactorial. These changes in vasoactivity have the potential to combine with other cardiovascular risk factors to enhance the development of atheroma.

Predictors of mortality from type 2 diabetes mellitus in Canterbury, New Zealand; a ten-year cohort study

The aim was to establish mortality rates in a cohort of subjects with type 2 diabetes mellitus over 10 years in Canterbury, New Zealand (NZ) and to determine baseline prognostic factors. Subjects (447) with type 2 diabetes (208 male, 239 female; age range 30-82 years, median 62 years; of predominantly European origin) were characterised in a clinic survey in 1989. Individual status (dead or alive) at June 1 1999 (10 year follow-up) was ascertained. Mortality rates were compared with the general NZ population and the relative risk (RR) of baseline prognostic factors evaluated with Cox's proportional hazards model. At 10 years, 232 subjects were confirmed as alive and 187 as dead - only 28 were untraceable. Ten year survival was 55% (95% CI: 50-60) for the cohort, compared with 70% (95% CI: 65-75) at 6 years. Factors assessed at baseline (1989), that were independently prognostic of total mortality, included age (RR 2.0, 95% CI: 1.6-2.5), pre-existing coronary artery disease (CAD; RR 1.7, 95% CI: 1.2-2.4) and albuminuria (RR 1.58, 95% CI: 1.1-2.3). Glycated haemoglobin was not a significant predictor of total mortality, although was a predictor of CAD mortality in those subjects free of CAD in 1989 (RR 1.6, 95% CI: 1.1-2.3). In the latter subset, independent prognostic factors for CAD mortality also included age (RR 2.5, 95% CI: 1.7-3.8), hypertension (RR 1.9, 95% CI: 1.0-3.7), peripheral vascular disease (RR 2.4, 95% CI: 1.3-4.5) and smoking (RR 2.6, 95% CI: 1.2-5.8). Increased mortality in type 2 diabetic subjects is therefore attributable to multiple risk factors. Improved outcomes will depend on interventions targeted at glycaemic and all other remediable factors.

Age at diagnosis, glycaemic control and the development of retinopathy in a population-based cohort of Type 1 diabetic subjects in Canterbury, New Zealand

The aim was to determine the relationship between age at diagnosis, glycaemic control and the development of retinopathy in a population-based cohort of Type 1 diabetic subjects. At 1 January 1984, there were 286 individuals with Type 1 diabetes (and age of onset<20 years) on the Canterbury, New Zealand population register who had at least 2 prospective HbA(1c) readings (from 1 January 1984). Of these, 107 already had retinopathy. Of the 179 subjects without retinopathy at baseline 63 developed retinopathy during follow-up. After controlling for duration of diabetes (in the whole group), age at diagnosis was found to be a significant predictor of HbA(1c) level (P=0.001), with higher (mean+/-SD) baseline HbA(1c) in the 10-14 age group (7.95+/-2.14%), compared with (7.62+/-1.77%) in the <10 year group and (7.39+/-2.57%) in the >14 year group. The major predictors of retinopathy (in those without retinopathy at baseline), however were duration of diabetes (mean time to development of retinopathy decreases by 14% (95% CI 10-17%) for each year), baseline HbA(1c) (for each unit increase, mean time to development of retinopathy decreased by 23% (95%CI 13-32%) and HbA(1c) slope (average annual change). Peri-pubertal age at diagnosis (10-14 years) did not influence the time to onset of retinopathy over and above that attributed to duration of diabetes and glycaemic control.

Type 2 diabetes towards the new millennium--the relative importance of glycaemic versus lipid control

The prevalence of type 2 diabetes is set to increase. The UKPDS has shown that better average glycaemic control over time leads to a reduction in microvascular complications. Macrovascular outcomes are also reduced in overweight subjects treated with metformin. The UKPDS and our own data, however, show that the natural history of type 2 diabetes is one of progressive deterioration in glycaemic control despite treatment. Lipid parameters emerges as the strongest predictors of outcomes in type 2 diabetes and suggest where therapeutic endeavours might best be directed. Ongoing trials of lipid-modifying therapies in type 2 diabetes will help to substantiate this. In the meantime, efforts to improve glycaemic control should not be pursued to the exclusion of other abnormalities that may have a greater relevance to outcomes of type 2 diabetes. There is an urgent need for better prevention and intervention strategies as we approach the new millennium.

Haemochromatosis gene mutations Cys282Tyr and His63Asp are not increased in Type 2 diabetic patients compared with the Canterbury (New Zealand) general population

Genetic predisposition to haemochromatosis may be an important aetiological factor in some cases of Type 2 diabetes. Our aim was therefore to test the hypothesis that the haemochromatosis gene mutations Cys282Tyr and His63Asp are more prevalent in Type 2 diabetic patients compared with the Canterbury, New Zealand general population. We studied 230 consecutive patients referred to the Diabetes Services with age > or = 30 years and considered to have Type 2 diabetes. DNA was extracted from whole blood and amplified by polymerase chain reaction prior to restriction fragment length polymorphism analysis. The frequency of the mutations was compared with that observed previously in 1064 subjects from the Canterbury general population by chi2 testing. Iron was measured by a colorimetric method, transferrin by rate nephelometry and ferritin by immunoassay. There were 2/230 (0.8%) Cys282Tyr homozygous subjects in the diabetic group compared with 5/1064 (0.5%) NS in the general population. Although there was a trend to lower incidence of Cys282Tyr heterozygosity in the diabetic group, there was no significant difference for any of the six genotype frequencies between the two groups. Haemochromatosis gene mutations Cys282Tyr and His63Asp are therefore not increased in Type 2 diabetics compared with the general population. Transferrin saturation was a sensitive marker (100%) of genetic haemochromatosis, although ferritin had low specificity (77.8%). Genetic susceptibility to haemochromatosis is not an important aetiological factor for diabetes, and targeted screening of diabetic patients for haemochromatosis is not indicated.

Growth hormone binding protein correlates strongly with leptin and percentage body fat in GH-deficient adults, is increased by GH replacement but does not predict IGF-I response

GH-binding protein (GHBP) corresponds to the extracellular domain of the GH receptor (GHR) and has been shown to be closely related to body fat. This study aimed to examine the inter-relationship between GHBP, leptin and body fat, and to test the hypothesis that GHBP is modified by GH replacement in GH-deficient adults and predicts IGF-I response. Twenty adults, mean age 47 years (range 20-69) with proven GH deficiency were randomly allocated to either GH (up to 0.25 U/kg/week in daily doses) or placebo for 3 months before cross-over to the opposite treatment. Plasma GHBP and leptin were measured at baseline and 2, 4, 8 and 12 weeks after each treatment. Whole body composition was measured at baseline by dual-energy X-ray absorptiometry (DEXA). There was a strong correlation between baseline leptin and GHBP (r = 0.88, P < 0.0001) and between baseline GHBP and percentage body fat, (r = 0.83, P < 0.0001). Mean GHBP levels were higher on GH compared with placebo, 1.53 +/- 0.28 vs 1.41 +/- 0.25nM, P = 0.049. There was no correlation between baseline IGF-I and GHBP (r = -0.049, P = 0.84), and GHBP did not predict IGF-I response to GH replacement. The close inter-relationship between GHBP, leptin and body fat suggests a possible role for GHBP in the regulation of body composition. GHBP is increased by GH replacement in GH-deficient adults, but does not predict biochemical response to GH replacement.

Clinical and biochemical outcomes of type 2 diabetes mellitus in Canterbury, New Zealand: a 6-year cohort study

There is a paucity of data regarding outcomes of Type 2 diabetes mellitus. A cohort of 447 Type 2 diabetic subjects (208 male, 239 female; age range 30-82 years, median 62 years; and of predominantly European origin) was characterised in a clinic survey in 1989. Individual status (dead or alive) at 1 June 1995 was ascertained. At 6 years, 289 subjects were confirmed as alive and 133 as dead--only 25 were untraceable. Of those subjects identified as alive, follow-up clinical and biochemical data were obtained for 253 (87.5%) individuals. In those subjects, glycated haemoglobin deteriorated from 63.1 +/- 18.7 mmol/mol haem in 1989 to 71.7 +/- 24.4 in 1995, P < 0.0001. An increased prevalence of retinopathy was evident at 6-year follow-up, 59.7% cases in 1995 compared with 39.5% in 1989, P < 0.001. Similarly there was an increased prevalence of coronary artery disease (CAD) (33.6 vs 18.2% of cases), albuminuria (26.5 vs 19% of cases; P < 0.001), and hypertension (71.5 vs 54.9% of cases; P < 0.001) in 1995 vs 1989, respectively. Multiple logistic regression analysis showed that glycated haemoglobin (odds ratio (OR) for 18 mmol/mol haem change, 1.78; 95% CI, 1.15-2.85), hypertension (OR, 3.33; 95% CI, 1.40-8.41) and known duration of diabetes (OR for 7 year change, 2.12; 95% CI, 1.24-3.80) were predictors for development of retinopathy. There is therefore a deterioration in glycaemic control in Type 2 diabetes over 6 years and an increased prevalence of complications that present strategies in a multidisciplinary specialist diabetes clinic are unable to prevent on a sustainable basis.

Lipid but not glycaemic parameters predict total mortality from type 2 diabetes mellitus in Canterbury, New Zealand

A cohort of 447 subjects with Type 2 diabetes mellitus (208 male, 239 female; age range 30-82, median 62 years; and of predominantly European origin) was characterized in a clinic survey in 1989. Individual status (dead or alive) at 1 June 1995 was ascertained. Mortality rates were compared with the general New Zealand population by calculating standardized mortality ratios (SMR) and the hazard ratio (HR) of prognostic factors evaluated with Cox's proportional hazards model. At 6 years, 289 subjects were confirmed as alive and 133 as dead; only 25 were untraceable. Six-year survival for the cohort was 70% (95% CI 66-74). SMR was 2.53 (95% CI 1.99-2.68) for the female cohort and 2.03 (95% CI 1.60-2.59) for the male cohort. Factors assessed at baseline (1989) that were independently prognostic of total mortality included age, male sex, pre-existing coronary artery disease (CAD) (HR 2.2, 95% CI 1.5-3.3) and plasma cholesterol (HR for 1.4 mmol l(-1) change: 1.49, 95% CI 1.2-1.9). HDL-cholesterol was protective in women (HR for 0.4 mmol l(-1) change: 0.72, 95% CI 0.51-1.00) but not men. Glycated haemoglobin was not a significant predictor of total mortality. Predictors of CAD mortality (in those subjects free of CAD in 1989) included plasma cholesterol (HR for 1.4 mmol l(-1) change: 1.86 95% CI 1.20-2.89), glycated haemoglobin (HR for 1.8% change: 1.9 95% CI 1.04-3.47), male sex, peripheral vascular disease, and smoking. There is therefore increased mortality in Type 2 diabetic subjects in Canterbury, New Zealand. HDL-cholesterol is protective against total mortality in females.

A population-based study of bone mineral density in women with longstanding type 1 (insulin dependent) diabetes

This study aimed to explore multiple determinants of BMD (bone mineral density) in 99 women with long-standing type 1 diabetes, recruited from a population based register of insulin users. BMD was measured using DEXA (dual energy X-ray absorptiometry) at the femoral neck and lumbar spine, age adjusted Z scores were calculated and results compared to those of healthy volunteers. The median age of diabetic subjects was 42 years and the median duration of diabetes was 27 years. BMD was positively associated with body mass index and height at both the lumbar spine and femoral neck. There was a positive association with oral contraceptive pill use and lumbar spine BMD, and peripheral vascular disease was negatively associated with femoral neck BMD. No correlation was seen with either age or duration of diabetes and absolute BMD values. Mean Z score at the femoral neck was -0.12 (95% confidence interval -0.37 to +0.12). At the lumbar spine, the corresponding value was -0.21 (-0.44 to +0.02). Pre- and post-menopausal values for the diabetic subjects and healthy volunteers were found to be similar. In summary, axial BMD values in subjects with long-standing diabetes were similar to those observed in healthy non diabetic populations.

Growth hormone replacement does not improve psychological well-being in adult hypopituitarism: a randomized crossover trial

In order to examine the effect of growth hormone (GH) on psychological parameters in adult hypopituitarism, 20 adults were studied, mean age 47 years (range 20-69) with hypopituitarism and confirmed GH deficiency (GH < 3 micrograms/l following clonidine 0.15 mg/m2). Subjects were randomly allocated to either GH-up to 0.25 U/kg per week in daily doses) or placebo for 3 months before crossover to the opposite treatment arm. Psychological parameters were assessed by self-reported questionnaires (Disease Specific Questionnaire (DSQ), the Symptom Checklist-90 (SCL-90), and the Social Adjustment Scale (SAS)) at baseline and monthly intervals to the end of the trial. Both SAS and SCL-90 total scores showed a significant decline with respect to time (p = .03 and .013 respectively), although this was not a function of active treatment. DSQ showed a trend to decline (p = .06), but no effect of active treatment. None of the subscale components of the SCL-90 showed any significant change on active treatment. Improvement in psychological parameters occurs as a function of enrolment to a clinical trial, rather than active GH replacement in adult hypopituitarism.

Low-dose brain natriuretic peptide infusion in normal men and the influence of endopeptidase inhibition

1. To assess the threshold dose for bioactivity of brain natriuretic peptide and the role of endopeptidase 24.11 in metabolism of brain natriuretic peptide at physiological plasma levels, we studied eight normal men receiving 2 h infusions of low-dose brain natriuretic peptide [0.25 and 0.5 pmol min-1 kg-1 with and without pretreatment with an endopeptidase inhibitor (SCH 32615, 250 mg intravenously)] in placebo-controlled studies. 2. Plasma brain natriuretic peptide increased 2-fold during the infusion of 0.25 pmol min-1 kg-1 (mean increment above control 3.9 pmol/l, P < 0.001), and tripled (P < 0.001) with 0.5 pmol min-1 kg-1. Plasma renin activity was inhibited by both doses (14.8%, P < 0.01, and 20%, P < 0.001, respectively). A significant natriuresis (56% increase in urine sodium/creatinine ratio, P < 0.02) occurred with the higher dose. Blood pressure, haematocrit, plasma cGMP, atrial natriuretic peptide and aldosterone were unaffected by either dose. 3. Compared with brain natriuretic peptide (0.5 pmol min-1 kg-1) alone, SCH 32615 pretreatment increased peak plasma brain natriuretic peptide (13.4 +/- 0.78 versus 12.4 +/- 0.86 pmol/l, P < 0.05), ANP (7.5 +/- 0.96 versus 5.9 +/- 0.4 pmol/l, P < 0.01) and cGMP (4.8 +/- 1.7 versus 3.9 +/- 1.4 nmol/l, P < 0.001). Plasma renin activity was further suppressed with SCH 32615 pretreatment (29% compared with 20%, P < 0.001). 4. Small acute increments in plasma brain natriuretic peptide (4 pmol/l) have significant biological effects in normal men without altering plasma atrial natriuretic peptide or cGMP.

Low-dose growth hormone replacement lowers plasma leptin and fat stores without affecting body mass index in adults with growth hormone deficiency

OBJECTIVE

The ob gene product, leptin, is considered to be a marker of adipose tissue mass and a possible homeostatic regulator of body mass. Our objective was to examine the effect of GH replacement on adipose tissue stores and leptin in adult hypopituitarism.

SUBJECTS

Twenty adults, mean age 47 years (range 20-69) with proven GH deficiency were randomly allocated to either GH (up to 0.25 U/kg/week in daily doses) or placebo for 3 months before cross-over to the opposite treatment.

MEASUREMENTS

Body composition was measured by dual-energy X-ray absorptiometry (DEXA) in the whole body, trunk and limbs. Plasma leptin was measured by radioimmunoassay at baseline and +2, +4, +8 and +12 weeks in each treatment arm.

RESULTS

Total body tissue fat (mean +/- SE) was 30.1 +/- 2.2% after GH compared with 31.9 +/- 2.2% after placebo, P < 0.001 (ANOVA). There were no significant changes in BMI (kg/m2), 29.1 +/- 1.3 after placebo vs 28.8 +/- 1.2 after GH; or waist to hip ratio (WHR), 0.91 +/- 0.01 after both placebo and GH. Baseline plasma leptin showed a significant correlation with baseline BMI, r = 0.67, P < 0.005 and baseline percentage total body fat, R = 0.89, P < 0.001. Plasma leptin (adjusted by using baseline percentage total body fat as a covariate) showed a significant linear decrease with time on GH compared with placebo (P = 0.03, ANOVA).

CONCLUSIONS

Plasma leptin and total body fat fall promptly in response to low-dose replacement of GH in GH-deficient subjects. Hormone-induced changes in leptin can occur in humans in the absence of change in body mass index.

Plasma cortisol, PRL, ACTH, AVP and corticotrophin releasing hormone responses to direct current cardioversion and electroconvulsive therapy

OBJECTIVE

We aimed to evaluate and contrast the hypothalamo-pituitary-adrenal (HPA) response to direct current (DC) cardioversion and electroconvulsive therapy (ECT).

SUBJECTS

Six male subjects (mean age 61.2 years, range 46-74) with chronic atrial fibrillation were selected for cardioversion. Six subjects with depression (one male, five female; mean age 43.2 years, range 31-59) were selected for ECT. Those taking glucocorticoid drugs, opiates or beta-adrenoceptor antagonists were excluded.

MEASUREMENTS

Patients attended for serial blood sampling on the day of cardioversion or ECT, and for an equivalent time period on a control day at least one week before. Intravenous propofol was given to each subject for anaesthesia on the day of cardioversion or ECT. On both study and control days, blood samples were taken at -30, -15, 0 (just prior to cardioversion or ECT), +5, +10, +15, +30, +60, +90 and +120 minutes for assay of cortisol, PRL, ACTH, AVP and CRH.

RESULTS

For cardioversion: plasma cortisol increased from 252.5 +/- 39.8 to a maximum of 721.3 +/- 50 nmol/l at 30 minutes (P < 0.0001 compared with control day). ACTH increased from 12.8 +/- 2.8 to a maximum of 64 +/- 14 pmol/l at 5 minutes (P < 0.0001 compared with control day). AVP increased from 6.6 +/- 3.3 to a maximum of 42.9 +/- 16 pmol/l at 5 minutes post-cardioversion (P < 0.005 compared with control day). PRL increased from 141 +/- 28 mlU/l to a maximum of 873 +/- 219 mlU/l at 10 minutes (P < 0.001 compared with control day). There was no significant difference in CRH responses between cardioversion and control days. There was no significant correlation between total electrical energy delivered and maximum ACTH and AVP responses (R = 0.54 and -0.13, respectively). For ECT: on the day of ECT plasma cortisol increased from 419.5 +/- 25.9 to a maximum of 614.7 +/- 26.9 nmol/l (P < 0.002 compared with control day). ACTH increased from 22.7 +/- 6.2 to a maximum of 77.8 +/- 19.1 pmol/l (P < 0.0003 compared with control day). PRL increased from 771 +/- 317 to a maximum of 3152 +/- 703 mlU/l (P < 0.001 compared with control day, and significantly greater than the peak response to cardioversion, P < 0.03). AVP increased from 13.0 +/- 10.8 to a maximum of 35.1 +/- 5.6 pmol/l (P < 0.02 compared with control day). There was no significant difference in CRH responses between ECT and control days. Peak cortisol and ACTH responses did not differ significantly between ECT and cardioversion. Baseline cortisol levels, however, were significantly higher in the depressed group compared with the cardioversion group, P < 0.02, but not ACTH or AVP.

CONCLUSION

Significant hypothalamic-pituitary-adrenal activation and PRL release occur in response to both cardioversion and ECT. AVP may have an important role in mediating the acute ACTH response to electrical stimulation.

Retinol binding proteinuria and phosphaturia: markers of paracetamol-induced nephrotoxicity

The occurrence of hypophosphataemia in paracetamol overdose suggests that nephrotoxicity is common, impaired renal tubular reabsorption of phosphate indicating renal damage. To investigate the potential nephrotoxicity of paracetamol, we studied 148 consecutive patients with paracetamol overdose. Serial clinical and biochemical measurements were made, and a fasting overnight urine collection was obtained for creatinine (Cr), phosphate and retinol-binding protein (RBP) determination. Renal threshold phosphate concentration (TmPO4/GFR) was determined from urinary parameters by an established nomogram. The degree of hypophosphataemia correlated with the severity of overdose, and with TmPO4/GFR. The median RBP/Cr ratio was higher in those patients exhibiting biochemical hepatotoxicity compared with those without hepatotoxicity, in whom median RBP/Cr was not significantly higher than controls. Within the group of patients showing biochemical hepatotoxicity, there was a correlation between log RBP/Cr and TmPO4/GFR. RBP/Cr ratio is a less sensitive marker of renal tubular toxicity than phosphaturia in these patients, and may indicate a different mechanism of toxicity.

Renal, endocrine, and hemodynamic interactions of atrial and brain natriuretic peptides in normal men

Brain natriuretic peptide (BNP) is a recently identified hormone that is secreted by the human heart and circulates in plasma with natriuretic, endocrine, and hemodynamic effects similar to those of atrial natriuretic peptide (ANP). To examine the interaction of human BNP with ANP, we studied eight normal men receiving constant infusions of ANP (2.0 pmol.kg-1.min-1 for 5 h), with and without superimposed infusions of BNP (2.0 pmol.kg-1.min-1 for 2 h), using a balanced random-order design. BNP infusions achieved plasma levels of 30-35 pmol/l at 90-120 min and were similar to levels observed in mild heart failure. Metabolic clearance rate of BNP (mean 4.6 +/- 0.4 l/min) and disappearance rate from plasma (t1/2 18.9 min) were similar to values determined previously in the absence of exogenous ANP. In contrast, the addition of BNP induced a progressive and reversible increase (50%) in steady-state plasma ANP. Compared with ANP alone, BNP induced an additional (50%) increase in sodium excretion (P < 0.05) and significant increases in both plasma (P < 0.001) and urine guanosine 3',5'-cyclic monophosphate (P < 0.01). Systolic blood pressure was lowered by the addition of BNP (P < 0.01) and continued to fall after cessation of BNP infusions. Despite this, the response of the renin-aldosterone and sympathetic nervous systems (heart rate and plasma catecholamines) was not significantly different on the two study days. As well as showing additive effects of the two natriuretic peptides, these studies point to important interactions of BNP on ANP metabolism at plasma levels observed in mild heart failure.

Bone mineral density is reduced in female but not male subjects with Addison's disease

AIMS

Bone mineral density (BMD) may be potentially reduced in Addison's disease as a result of excessive glucocorticoid replacement, loss of adrenal androgens or concomitant gonadal or thyroid disease. We have examined clinical and biochemical parameters, and BMD in a group of subjects with Addison's disease.

METHODS

Fourteen patients (9 female mean age 56 years, 5 male mean age 56.6 years) with primary adrenocortical failure (median duration 8.5 yrs) on replacement therapy were studied. Four had hypothyroidism on thyroxine doses (0.1 to 0.15 mg/d). Seven of the 9 females were post menopausal. Mean plasma cortisol levels were calculated from at least five samples in each subject drawn between 3 and 5 hours post dose, and the cortisol replacement dose calculated per unit body mass (mg/kg). BMD was measured by dual energy X-ray absorptiometry (DEXA) at femoral neck and lumbar spine (L2-4) and compared with local reference data.

RESULTS

For women (n = 9) at L2-4 the mean Z score was -1.21 (95% CI -1.69, -0.73), and at femoral neck -0.57 (95% CI -1.15, 0.00). For men (n = 5) at L2-4, the mean Z score was 1.32 (95% CI -0.86, 3.50) and at femoral neck 0.62 (95% CI -0.18, 1.42). For all patients, there was no significant correlation between mean plasma cortisol and Z scores at L2-4 and femoral neck, r = -0.003 and -0.095 respectively; and between duration of Addison's disease and mean Z scores at L2-4 and femoral neck r = -0.043 and 0.143 respectively.

CONCLUSIONS

Women with Addison's disease therefore have a greater than expected reduction in BMD. We postulate that this may be related to loss of adrenal androgens.

Glucocorticoid responsive ACTH secreting bronchial carcinoid tumours contain high concentrations of glucocorticoid receptors

Cushing's syndrome due to a bronchial ACTH secreting carcinoid tumour may be difficult to distinguish from a pituitary microadenoma (corticotrophinoma) causing Cushing's disease, since in both disorders ACTH secretion may be responsive to glucocorticoids. Why some bronchial carcinoid tumours are responsive is unknown but it could be because of co-secretion of corticotrophin releasing factor (CRF) and/or expression of glucocorticoid receptors. We report two patients with glucocorticoid responsive ACTH secreting bronchial carcinoid tumours, neither of whom produced or responded to CRF. Significant glucocorticoid receptor binding capacity (92 and 102 pmol/g protein), compared with control lung tissue, was found in extracts from both tumours. These findings suggest that corticotrophinoma-like responses to glucocorticoids observed in some ACTH secreting bronchial carcinoids result from expression of glucocorticoid receptors and are not necessarily related to the production of CRF.