Rickets Year 4 Paediatrics Notes OmpathStudy

Rickets Year 4 · Paediatrics Collection: 4TH YEAR ALL NOTES / PAEDS / PAEDS 4.3 / Munge / NUTRITION -- Slide 1 Rickets Dr Rose Munge Slide 2 Objectives of the lecture To discuss linear growth and the role of vitamin D\nto discuss metabolism of vitamin D To discuss the pathophysiology of rickets and osteomalacia Discuss briefly on diagnosis and management To briefly go through other micronutrient deficiencies Slide 3 Introduction Bone is the major reservoir of calcium, phosphorus, magnesium, sodium and other ions The skeleton contains osteoid and osteocalcin proteins which take part in bone calcification Osteocalcin synthesis is Vitamin D and Vitamin K dependant Osteoid is a collagen containing protein on which is deposited a crystalline mineral phase Slide 4 Linear growth Bone develops in 2 different ways a) Endochondral ossification( axial and appendicular bones) Intermembranous ossification( skull, clavicle).\nBones without physes ( pelvis, carpals) grow by apposition from their surrounding perichondrium/osteum while others such as phalanges and spine use both Slide 5 Bone growth in children occurs via calcification of cartilage cells (chondrocytes) present at the end of the bone (growth plates) Calcium and phosphorus are deposited from serum to the chondrocytes which undergo mineralization Vitamin D and parathyroid hormones act to ensure that ECF(extracellular fluid) calcium and phosphorus concentrations are at appropriate levels to permit mineralization Slide 6 Hormones that regulate growth and mineralization: Vitamin D (main) Parathyroid hormone Growth hormone acting through insulin-like growth factors Thyroid hormone Insulin Leptin Androgens and estrogens(mostly during adolescence) Slide 7 Bone growth patterns occur at: Acceleration of length of the limbs in prepubescence Growth of the trunk during early adolescence Increased bone mineral deposition in late adolescence Slide 8 Vitamin D metabolism Sources of Vitamin D Diet Cutaneous synthesis Slide 9 Diet Plant\nErgocalciferol (Vitamin D2) Animal sources\nCholecalciferol (Vitamin D3)\nMilk – for young children(breast milk, though lower than recommended daily requirements – 12-60 iu/L) Supplementation(200-400iu/day) Slide 10 Cutaneous synthesis Usually worse in dark skinned individuals who require 3-6times more exposure time due to increased melanin Exposure to the noon sun (10-15minutes) at least 2 days in a week. Studies show that anytime near solar noon is the best time for exposure(10am to 2pm). This is because the UVB rays are at the highest at noon, lower in the morning and evening. Slide 12 Metabolism of Vitamin D Skin contains 7 dehydrocholesterol which is converted by ultraviolet radiation(sunlight) to cholecalciferol (Vitamin D3). Vitamin D3 is then released into the blood stream and transported to the liver via Vitamin D Binding Protein\nIn the liver(hepatocytes), the Vitamin D2 and Vitamin D3are converted by hepatic microsomal enzyme(NADPH) and magnesium to 25-hydroxycholecalciferol Slide 13 Then 25-hydroxycholecalciferol is transported in the blood stream via VDBP to the kidneys for further hydroxylation Hydroxylation in the kidneys occurs at the PCT(proximal convoluted tubules) and depends on the serum level of Ca2+ and PO4- as well as PTH 25-hydroxycholecalciferol is converted dihydrocholecalciferol(1,25) Slide 14 When serum levels of calcium and phosphate are low, and PTH is high then dihydroxycholecalciferol will be produced which will act on the intestines to increase absorption of calcium. 1,25(OH)2 D is only 0.1% of 25(OH) D.\nWhen 1,25(OH)2 D is high, calcium and phosphate are high, then it is converted to it’s inactive form 24,25(OH)2 which is the excreted out of the body Slide 15 Summary of metabolism Slide 16 Rickets Definition - deficient mineralization of osteoid at the growth plates, which slows growth and eventually causes bone age retardation\n Osteomalacia is inadequate mineralization of mature bone Studies have shown that both in the west and in the developing world, the prevalence of rickets is RISING Slide 17 PATHOPHYSIOLOGY Thickening of the growth plate: due to lack of mineralization of the increasing cartilage without mineralization There is an increase in the circumference of the growth plate and the metaphysis There is general softening of the bone that causes them to bend easily on weight bearing or muscle pull Slide 18 aetiology Vitamin D disorders Calcium deficiencies Phosphate deficiencies Renal losses\nHereditary hypophosphatemic rickets\nFanconi syndrome\nDent disease: mutant gene for renal Cl- channel\nDistal renal tubular acidosis Slide 19 Vitamin D disorders Nutritional – worth noting that exclusive breastfeeding can lead to vitamin D deficiency if the child is kept indoors Congenital deficiency (Vitamin D dependant deficiency type 1 and type 2) Malabsorption Chronic renal failure Slide 20 Calcium deficiency Low dietary intake Malabsorption – either inhibitors of calcium intake or GIT disorders that interf