Letters to the Editor Indian Pediatrics 2003; 40:174-175 |
Reply |
Khandori et al. have expressed concern regarding the absence of data on the levels of vitamin D (25-hydroxy and 1, 25 dihydroxy-vitamin D3) and iPTH. In this study iPTH levels were performed in patients with hypocalcemia with normal renal function and magnesium levels, who did not have clinical and radiological features of rickets. PTH levels were performed in 24 out of 29 patients. Fifteen patients with elevated PTH levels were classified as pseudohypoparathyroidism (PHP) and 9 with low PTH levels were diagnosed as hypoparathyroidism (HP) in accordance to the diagnostic criteria provided in the article(1). Hypocalcemia in the presence of hyperphosphatemia and normal renal function is diagnostic of inefficient PTH action(2). PTH level helps in classifying these patients into HP (low) and PHP (high). Vitamin D metabolite levels as well as phosphaturic and c-AMP response to PTH although important in laboratory evaluation of parathyroid function, are not essential for clinical diagnosis of HP or PHP(2). Levels of vitamin D metabolites are important in evaluation of patients with hypocalcemic rickets. Normal level of 25-hydroxyvitamin D3 is against the diagnosis of nutritional rickets and points towards the diagnosis of vitamin D refractory rickets (VDDR). Levels of 1,25 dihydroxyvitamin D3 is useful in further classification of VDDR into VDDR 1 (low) and VDDR II (high). In the present series 4 patients had clinical and radiological features of rickets. Levels of 25-hydroxyvitamin D3 were normal in all these patients indicating the diagnosis of VDDR. We did not classify these patients into VDDR 1 and VDDR II as 1,25 dihydroxy-vitamin D3 levels were not performed due to cost constraints. In this regard response to vitamin D metabolites (1-hydroxyvitamin D3 or 1, 25 dihydroxyvitamin D3) is a reasonable alternative to estimation of vitamin D metabolites for classification of VDDR. VDDR 1 responds to physiological doses of 1 hydroxyvitamin D3 while the requirements are much higher in VDDR II.
Rule out tumor lyses/rhabdomyolysis drugs/phosphate load
Normal/Low Elevated
Yes No Deranged Normal Blood gas Magnesium CRF PTH Liver function Malabsorption studies Low High
*Response to 1-hydroxyvitamin D3 therapeutic alternative to diagnosis. Fig 1. Approach to Hypocalcemia
Jyoti Sharma, |
References |
1. Sharma J, Bajpai A, Kabra M, Menon PSN. Hypoalcemia - Clinical, Biochemical, Radio-logical Profile and Followup in a Tertiary Hospital in India. Indian Pediatr 2002; 39: 276-282.
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