Based on strong evidence, vitamin D comes from the diet and sunlight. It is activated by the liver and kidney. (2) Based on expert opinion, pediatric vitamin D reference ranges are controversial. (4) Based on strong evidence, rickets is inadequate mineralization in a growing bone. There are multiple risk factors for vitamin D-deficient rickets. (4) Based on strong evidence, laboratory findings in the different types of rickets can point to the etiology, the most common of which is nutritional. (6) Based on expert opinion, there are multiple protocols for treating nutritional rickets, and nonnutritional forms are treated differently. (7) Based on strong evidence, parathyroid hormone (PTH) is regulated by changes in serum calcium levels and signals through a G protein-coupled receptor. (8) Based on strong evidence, PTH acts at the bone and kidney to raise serum calcium levels (13)(14). Whereas phosphorus is also released from bone in response to PTH, phosphorus excretion is increased in the kidney with the net effect of lowering the serum phosphorus level (15). In hypoparathyroidism, low PTH levels result in low serum calcium levels. Signs include Chvostek and Trousseau signs, and severe hypocalcemia can cause tetany and seizures. (2) Based on strong evidence, primary hypoparathyroidism can be due to inherited disorders or acquired by neck surgery, autoimmune disease, or metal or tumor infiltration. (2) Based on strong evidence, pseudohypoparathyroidism is a disorder of PTH resistance characterized by low serum calcium levels despite elevated PTH levels. Type 1a is caused by mutations in GNAS1 and is associated with Albright hereditary osteodystrophy. Type 1b is caused by defects in GNAS1 imprinting and does not result in osteodystrophy. Treatment is with calcium and calcitriol. (11) Based on strong evidence, fibroblast growth factor 23 (FGF23) helps regulate plasma phosphate concentration (16). High phosphate and 1,25-dihydroxyvitamin D levels are its stimulators (17). Based on strong evidence, FGF23 decreases the production of cotransporters in the kidney that normally prevent phosphate wastage, and it downregulates the production of 1,25-dihydroxyvitamin D, which increases gut absorption (17). Based on strong evidence, there are multiple causes, most genetic, of excess FGF23 production, all leading to hypophosphatemia and ultimately rickets.
ASJC Scopus subject areas
- Pediatrics, Perinatology, and Child Health