Search

Systematic study of hyperfiltration in diabetic nephropathy has been hindered by the lack of a simple glomerular filtration rate (GFR) measure that is accurate in this range of renal function. Serum cystatin C (GFR(CYSTATIN C) ) reflects long-term trends in GFR in normal or elevated ranges. To test whether it can reflect acute changes, we examined the impact of clamped hyperglycaemia on GFR(CYSTATIN C) and GFR(INULIN) in subjects with Type 1 diabetes.GFR(INULIN) and GFR(CYSTATIN C) were measured in 32 normotensive, normoalbuminuric subjects during clamped euglycaemia and hyperglycaemia. For comparison, GFR(MDRD) was estimated according to the four-variable equation.During clamped euglycaemia, agreement between GFR(CYSTATIN C) and GFR(INULIN) was excellent, with mean bias +1.9 (90% distribution -29 to +31) ml min(-1) 1.73 m(-2), while GFR(MDRD) had mean bias +11.4 (-45 to +51) ml min(-1) 1.73 m(-2). With exposure to clamped hyperglycaemia, the mean increase in GFR(CYSTATIN C) (+17.5 ± 13.5 ml min(-1) 1.73 m(-2) ) reflected that observed with GFR(INULIN) (+15.3 ± 28.1 ml min(-1) 1.73 m(-2), P = 0.74), while GFR(MDRD) demonstrated a mean decline of -4.4 ± 33.6 ml min(-1) 1.73 m(-2) (P = 0.01). In all 24 subjects in whom GFR(INULIN) increased in response to hyperglycaemia, GFR(CYSTATIN C) reflected a concordant change (sensitivity, 100%) while GFR(MDRD) increased in 10/24 (sensitivity, 42%). In the eight remaining subjects, specificity was 25 and 75% for GFR(CYSTATIN C) and GFR(MDRD), respectively.GFR(CYSTATIN C) reflects normal and elevated renal function better than GFR(MDRD) even under the acute influences of hyperglycaemia, suggesting a role for cystatin C in clinical practice and research for the study of early renal function changes in Type 1 diabetes.

Conventional therapy of hypophosphataemic rickets (HR) with oral phosphate and calcitriol does not always result in normal linear growth. Recombinant human growth hormone (rhGH) offers theoretical advantages as an adjunctive therapy. We aimed to determine the effects of adjunctive rhGH therapy in children with well-controlled HR.In this report, 5 prepubertal children (aged 3.5-10.9 years) with well-controlled HR on conventional therapy were given adjunctive standard dose rhGH therapy for one year.Height, growth velocity, metabolic markers of calcium and phosphate metabolism, body composition, bone mineral density, wrist and knee X-rays, and renal sonography were assessed at regular intervals. Height and growth velocities were also calculated 12 months after ceasing rhGH therapy.After 12 months therapy with rhGH, no significant biochemical or radiological benefits were observed. A significant increase in height SD score was observed (P = 0.023), but this was not associated with any increase in the growth velocity SD score and appears to have been due to catch-up growth caused by conventional therapy alone. When rhGH therapy was ceased, no significant decreases in mean height SD or growth velocity SD scores were observed.In well-controlled hypophosphataemic rickets patients receiving conventional therapy, adjunctive therapy with standard dose rhGH offers no benefits in linear growth or rachitic disease markers.

The apparent decline over the last decade of vitamin D deficiency rickets among black infants in South Africa has suggested a significant improvement in their vitamin D status. Levels of serum 25-hydroxy-vitamin D, calcium, phosphorus and alkaline phosphatase, together with a radiograph of the left wrist, were obtained in 114 hospitalized black infants under the age of 2 years in order to establish the frequency of infants with or at risk of vitamin D deficiency. Mean 25-hydroxyvitamin D levels were found to be in the low normal range and showed no correlation with either age or season. Vitamin D stores were depleted in 7% and relatively deficient in 20,7% with suggestive radiological features of rickets in only 2 patients. The high prevalence of malnutrition and infection made a biochemical assessment of rickets impossible. The significance of these suboptimal vitamin D levels is uncertain, but the available literature would suggest that these infants are at increased risk of developing vitamin D deficiency rickets.