Parathyroid function in vitamin D deficiency rickets. I. Phosphorus excretion index in vitamin D deficiency rickets in South African Bantu infants
Taitz, L.S.; De Lacy, C.D.
Pediatrics 30: 875-883
1962
ISSN/ISBN: 0031-4005 PMID: 13980239 Document Number: 573692
Patients with rickets, chosen on the criteria of craniotabes, rachitic rosary and expansion of distal metaphyses of the forearm, were 43 urban Bantu children aged from 4 months to 2 years. A normal group was of 8 infants without signs of malnutrition or rickets. Phosphorus excretion index was measured by the method of Nordin and Fraser (Lancet, 1960, i, 947), and Ca infusion tests were made in 5 infants by the method of Nordin and Fraser (Abst. 2319, Vol. 25). The phosphorus excretion index relates renal clearance of P to glomerular filtration rate and is a function of tubular re-absorption capacity for P and indirectly of parathyroid function. Only 6 of 37 subjects with active rickets had values within the range found in the normal group, and most had values significantly higher. In healing rickets values were significantly lower than in active rickets, but were still significantly above normal. The rachitic children had serum Ca values from 2.5 to 4.8 m-equiv. per litre, mean 3.5, compared with 4.2 to 4.8, 4.5 for the control group. Alkaline phosphatase was above 25 King Armstrong units in all but 3 of the subjects with active rickets, below that in all but one of those with healing rickets and in all the normal group. Patients with plasma inorganic P values above 3.5 mg per 100 ml had significantly lower phosphorus excretion indices than patients with low serum P values. In each patient given Ca infusion there was a fall of phosphorus excretion index, with no change of plasma inorganic P or a rise, returning to initial values within 24 h. Differences between rickets and primary hyperparathyroidism are discussed in their possible relation to two separate effects of the parathyroid hormone, on bone and on the kidneys (see Title 3988, Vol.