Vitamin D Deficiency Rickets Fan Yang Associated Professor Pediatric Department
Vitamin D Vitamin D comprises a group of sterols Vitamin D 2 = ergocalciferol Completely synthetic form produced by the irradiation of the plant steroid ergosterol Vitamin D 3 = cholecalciferol Produced photochemically by the action of sunlight or ultraviolet light from the precursor sterol 7-dehydrocholesterol Vitamin D = calciferol
VITAMIN D Humans & animal utilize only vitamin D3 & they can produce it inside their bodies from cholesterol. Cholesterol is converted to 7-dehydro- cholesterol (7DC), which is a precursor of vitamin D3.
VITAMIN D Exposure to the ultraviolet rays in the sunlight convert 7DC to cholecalciferol. Vitamin D3 is metabolically inactive until it is hydroxylated in the kidney & the liver to the active form 1,25 Dihydroxycholecalciferol. 1,25 DHC acts as a hormone rather than a vitamin, endocrine & paracrine properties.
Vitamin D: The Sunshine Vitamin Not always essential Body can make it if exposed to enough sunlight Made from cholesterol in the skin
Formation of Vitamin D Skin (UV light) 7-dehydro cholesterol Vitamin D 3 Ergosterol Vitamin D 2 Liver OH-group added 25-Hydroxy vitamin D 3 Storage form of vitamin (~3 months storage in liver) Kidney OH-group added by 1-hydroxylase 1,25-dihydroxy vitamin D 3 Active form of vitamin D, a steroid hormone OH-group added by 24-hydroxylase 24,25-dihydroxy vitamin D 3 Inactive form of vitamin D, ready for excretion
FUNCTIONS Calcium metabolismCalcium metabolism: vitamin D enhances ca absorption in the gut & renal tubules. Cell differentiationCell differentiation: particularly of collagen & skin epithelium ImmunityImmunity: important for Cell Mediated Immunity & coordination of the immune response.
Vitamin D - Functions Bone development Calcium absorption (small intestine) Calcium resorption (bone and kidney) Maintain blood calcium levels Phosphorus absorption (small intestine) Hormone Regulation of gene expression Cell growth
GROUPS AT RISK Infants Elderly Dark skinned Covered women Kidney failure patients Patients with chronic liver disease Fat malabsorption disorders Genetic types of rickets Patients on anticonvulsant drugs
Vitamin D deficiency Deficiency of vitamin D leads to:Deficiency of vitamin D leads to: Rickets in small children. Osteomalacia Osteoporosis
Parathyroid Hormone (PTH) Calcium-sensor protein in the thyroid gland Detects low plasma calcium concentrations Effects of parathyroid hormone Urine / kidneys Increases calcium reabsorption Increases phosphorus excretion Stimulates 1-hydroxylase activity in the kidneys 25-OH D 1,25-(OH) 2 D PTH required for resorption of Ca from bone Activates a calcium pump on the osteocytic membrane Activates osteoclasts
Pathogenesis Vitamin D deficiency Absorption of Ca, P Serum Ca Function of Parathyroid
Pathogenesis PTH High secretion P in urine Decalcification of old bone P in blood Ca in blood normal or low slightly Ca, P product Rickets
Pathogenesis Low secretion of PTH Failure of decalcification of bone Low serum Ca level Rachitic tetany
Clinical manifestation Rickets is a systematic disease with skeletons involved most, but the nervous system, muscular system and other system are also involved.
Clinical manifestation Early stage Usually begin at 3 months old Symptoms: mental psychiatric symptoms Irritability, sleepless, hidrosis Signs: occipital bald Laboratory findings: Serum Ca, P normal or decreased slightly, AKP normal or elevated slightly,25(OH)D3 decreased Roentgenographic changes: normal or change slightly
Clinical manifestation Advanced stage On the base of early rickets, osseous changes become marked and motor development becomes delayed. 1. Osseous changes: 1) Head: craniotables, frontal bossing, boxlike appearance of skull, delayed closure of anterior fontanelle 2) Teeth: delayed eruption, with abnormal order, defects 3) Chest: rachitic rosary, Harrisons groove, pigeon chest, funnel-shaped chest, flaring of ribs
Clinical manifestation 4) Spinal column: scoliosis,kyphosis, and lordosis 5) Extremities: bowlegs,or knock knee, greenstick fracture 6) Rachitic dwarfism 2. Muscular system: potbelly, late in standing and walking 3. Motor development: delayed 4. Other nervous and mental symptoms
Clinical manifestation Laboratory findings: Serum Ca and P decreased Ca and P product decreased AKP elevated Roentgenographic changes: Wrist is the best site for watching the changes. Late appearance of ossification center Widening of the epiphyseal cartilage Blurring of the preparatory calcification line metaphyses like a cup rarefaction of the bone thinned cortex of the shaft of long bone
Clinical manifestation Healing stage: Symptoms and signs of Rickets alleviate or disappear by use of appropriate treatment. The blood chemistries become normal, except AKP may be slightly elevated. Sequelae stage: All the clinical symptoms and signs disappear. Blood Chemistries and X-ray changes are recovered, but osseous deformities may be left. Usually seen in Children after 3 years old.
Rachitic vs. normal chick Rickets due to deficiency of vitamin D, Ca, or P
Treatment 1. Food and nursing care 2. Prevention of complications 3. Special therapy 1) Vitamin D therapy A. General method Vitamin D 2000-4000IU/day for 2-4 weeks, then change to preventive dosage (400IU). B. A single large dose: For severe case, or Rickets with complication, or those who cant bear oral therapy. Vitamin D3 200000-300000IU, im, preventive dosage will be used after 2-3 months.
Treatment 2) Calcium supplementation: only used for special cases, such as baby fed mainly with cereal, or infants under 3 months of age, and those who have already developed tetany. Dosage:1-3 g/day. 3) Plastic therapy: In children with bone deformities after 4 years old plastic surgery may be useful.
Prevention 1. Pay much attention to the health care of pregnant and lactating women, instruct them to take adequate amount of vitamin D. 2. Advocate sunbathing 3.Advocate breast feeding, give supplementary food on time
Prevention 4. Vitamin D supplementation: In prematures, twins and weak babies, give Vitamin D 800IU per day, For term babies and infants the demand of Vitamin D is 400IU per day, For those babies who cant maintain a daily supplementation, inject muscularly Vitamin D3 10000-200000 IU.
Prevention 5. Calcium supplementation: 0.5-1gm/day, for premature, weak babies and babies fed mainly with cereal
Sources of Vitamin D Sunlight is the most important source Fish liver oil Fish & sea food (herring & salmon) Eggs Plants do not contain vitamin D3
Vitamin D - Sources Not found naturally in many foods Synthesized in body Plants (ergosterol) Sun-cured forages Fluid milk products are fortified with vitamin D Oily fish Egg yolk Butter Liver Difficult for vegetarians
TOXICITY Hypervitaminosis DHypervitaminosis D causes hypercalcemia, which manifest as: Nausea & vomiting Excessive thirst & polyuria Severe itching Joint & muscle pains Disorientation & coma.
Vitamin D Toxicity Calcification of soft tissue Lungs, heart, blood vessels Hardening of arteries (calcification) Hypercalcemia Normal is ~ 10 mg/dl Excess blood calcium leads to stone formation in kidneys Lack of appetite Excessive thirst and urination Infants: