Urinary cyclic AMP corrected for glomerular filtration rate in the differential diagnosis of hypercalcemia

Methotrexate and its mechanisms of action in inflammatory arthritis

Despite the introduction of numerous biologic agents for the treatment of rheumatoid arthritis (RA) and other forms of inflammatory arthritis, low-dose methotrexate therapy remains the gold standard in RA therapy. Methotrexate is generally the first-line drug for the treatment of RA, psoriatic arthritis and other forms of inflammatory arthritis, and it enhances the effect of most biologic agents in RA. Understanding the mechanism of action of methotrexate could be instructive in the appropriate use of the drug and in the design of new regimens for the treatment of RA. Although methotrexate is one of the first examples of intelligent drug design, multiple mechanisms potentially contribute to the anti-inflammatory actions of methotrexate, including the inhibition of purine and pyrimidine synthesis, transmethylation reactions, translocation of nuclear factor-κB (NF-κB) to the nucleus, signalling via the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway and nitric oxide production, as well as the promotion of adenosine release and expression of certain long non-coding RNAs.

Differential laboratory diagnosis of hypercalcemia

It is proposed that this review will adopt the following format: establishment of hypercalcemia. This demands a discussion of the problem of normal ranges, the usage of either total calcium or ionized calcium in making this decision and where total calcium is used whether adjustment of this value for serum protein concentration should be used and if so, the formulae which have been cited to perform this. Having established hypercalcemia why is it necessary to differentiate this? This will involve reviewing those clinical situations in which differentiation of hypercalcemia has been attempted and will include an attempt to produce an up to date indication of conditions in which hypercalcemia has been described. When hypercalcemia has been established the laboratory tests which have been further used to discriminate will be divided into single tests such as N- or C- terminal parathormone, 1,25- dihydroxycholecalciferol, cyclic AMP; the combination tests which have been used including phosphate clearance, chloride vs. bicarbonate etc. proceeding to those groups which have used discriminant function to help in the decision making; dynamic testing will also be discussed particularly with reference to steroid suppression but will also include other known suppressants such as Mithramycin and Calcitonin. A final section will be included attempting to assess overall the present state of art in differentiating laboratory diagnosis of hypercalcemia and will also attempt to highlight those areas which appear to be most fruitful areas of progress in the future.

A calcium clamp technique in man

Calcium infusion imply a risk for cardiovascular complications. To avoid the risk, we have developed a new method for calcium infusion in man which can keep ionized calcium concentration in whole blood (WB-Ca++) in a steady state at a predetermined level. A solution of calcium chloride (Calcii chlor. Nord.), containing 0.117 mmol Ca++/ml water, is infused intravenously by means of an IMED 922H infusion pump. WB-Ca++ is determined every 5-10 min with a calcium ion-selective electrode, NOVA 2. The infusion rate is continuously adjusted. With the same initial infusion rate, 0.31 mmol Ca++/kg b.w./hour, hypercalcemia that is WB-Ca++ above 1.27 mmol/l was reached within 10 min in healthy volunteers, 8 females with a mean age of 26 years (range 19-36) and 7 males with a mean age of 29 years (range 25-34). The presettled WB-Ca++ level, 1.45 mmol/l, was obtained within 25 min and maintained in a steady state for 155 min at 1.45 +/- 0.01 mmol/l (mean +/- SE) in the female and at 1.46 +/- 0.01 mmol/l in the males. The range of the individual steady state mean WB-Ca++ was 1.42 +/- 0.02 mmol/l. No side-effects of the infusion were noted except for a slight increase in systolic and diastolic blood pressure 60 min after start of the infusion. In conclusion, the calcium clamp technique is safe and suitable for such situations where a presettled easily controlled WB-Ca++ level is required.