[Calcium, phosphorus, hydroxyproline and nitrogen in inflammatory joint diseases]

The elimination of calcium, phosphorus, hydroxyproline and nitrogen was studied in 127 patients with inflammatory joint diseases and )6 healthy controls for 4 days. On the third day, 186 mg of calcium was administered intravenously. Provoked hypercalciuria tests were made in 35 males, 116 females with rheumatiod arthritis (RA), 18 males with ankylosing spondylitis (ASp), 8 postinfectious arthritis (PA) and 18 healthy controls (C). In 120 patients comparison was made between the ratios of eliminated P/hydroxyproline, Ca/hydroxyproline and P/Ca with regards to the results obtained in healthy controls. The kinetics of 47Ca were studied in 7 males with ASp and 4 C. The ratios Ca/P in serum and P/Ca in urine were studied in the same patients and compared with 21 C. The results show that the bone symptomatology of PA manifests itself by elimination of elevated amounts of all of the indicators studied, especially phosphorus. In RA there may be considerable oscillations of flow of urine due to the perspiration of patients. RA differs from decompensated coxarthrosis and gonarthrosis in that the patients eliminate significantly less calcium and phosphorus. Corticosteroids stimulate the elimination of hydroxyproline. Younger patients with RA (25-44) show changes compatible with osteoporosis, older females (45-64) display changes similar to those seen in osteomalacia, the oldest female patient (65-84) appear to have insufficient binding capacity for calcium. The hyposthesis is proposed that at the disease onset RA is characterized by an extremely marked syndrome of osteopathy. ASp is characterized by significantly reduced elimination of hydraxyproline, higher metabolic pool of calcium, lower elimination of calcium in urine and faeces and lower accretion to bone.