Metabolic bone diseases

By Dr. Abdelaty Shawky Dr. Gehan Abdel-Monem

Bones…. What do they need to be strong?

• Calcium/ PO4• Vit D• PTH• calcitonin

Sources of Vitamin D and importance

* VIT D LEVEL IN SERUM:

• 25 (OH) D3 level ng/mlDEFICIENT < 10

INSUFFICIENT 10 - 20

OPTIMAL 20 - 60

HIGH 60 - 90

TOXIC >90

Vitamin D Deficiency in Saudi Arabia

Group mostly affected are:• Breast- Fed infants because Human milk contains

little vitamin D, • Age < 2 years• Darked –skin children because darkly pigmented

skin, which blocks penetration of ultraviolet light necessary for formation of cholecalciferol (Vit. D3) from cholesterol in the skin.

• Low socio-economic Class• Urban > Rural

PARATHYROID HORMONE (PTH)

• PTH increases the blood calcium level by:

1. Promoting bone resorption process.

2. Increasing calcium absorption from intestine by increasing the

synthesis of active vit D 3.

• PTH also stimulates the excretion of phosphates by the

kidneys.

CALCITONIN

• It is produced by para follicular c cells of thyroid.

• It is a calcium lowering hormone in serum by

inhibiting bone resorption by decreasing the number

& activity of osteoclasts .

Metabolic bone Diseases

• Rickets• Osteomalacia• osteoporosis

Rickets:• Disease of growing bones of children(epiphyseal

plate not closed )in which defective mineralization occurs in both bone and cartilage of epiphyseal growth plate.

Osteomalacia:• Disorder of mature bones in adult (after epiphyseal

plate closure )in which mineralization of new osteoid bone is inadequate or delayed

* Causes of rickets:1. Nutritional deficiency:

- Excess of phytate in diet which form insoluble compounds with

calcium so prevent its absorption (chapati flour)

2. Malabsorption: as in Celiac disease, Pancreatic insufficiency

3. Hepato-biliary diseases:

– Biliary Atresia.

– Cirrhosis.

– neonatal hepatitis.

4. Drugs:

– Anti-convulsants.

– Phenobartbitone.

– Phenytoin

5. Chronic renal causes :

-Renal osteodystrophy

* Types of Rickets:

(1). Vitamin D deficient rickets: there is decrease in vitamin D inside body.

(2). Vitamin D dependent rickets: there is defect in the process of vitamin D activation. (3). Vit D resistant rickets: either -Hypophosphatemic rickets. - End organ resistance to 1,25 Dihydroxy Vit D3.

Vitamin D deficient rickets

• The predominant cause of rickets is a deficiency in vitamin D, which is required for normal calcium absorption from the gut.

• Malabsorption leads to low levels of calcium in the blood. This not only prevents proper bone growth, but can also lead to calcium being released form the bones to increase its blood level.

Hypophosphatemic rickets

• Nutritional phosphate deficiency.• Prematurity. • Decreased intestinal absorption of phosphate

– Ingestion of phosphate binders (aluminum hydroxide).

• Renal phosphate wasting.

Diagnosis of rickets

A. Clinical features of rickets: (1). Skeletal manifestations (2). Extr-askeletal manifestationsB. Investigations.

(1). Skeletal manifestations

• Craniotabes: The earliest sign of rickets in infant, is (abnormal softness of skull)

• Delayed closure of anterior fontanel.• Frontal and parietal bossing: Rounded prominence of the

frontal and parietal bones in an infant’s cranial vault• Delayed eruption of primary teeth.• Enamel defects and caries teeth.• Rachitic rosary

– Swelling of the costo-chondral junctions.

• Harrison’s groove:– Lateral indentation of the chest wall at the site of

attachment of diaphragm.• Enlargement of long bones around wrists and ankles• Bow legs • knock knees• Green stick fractures• Deformities of spine, pelvis and leg – rachitic

dwarfism• Growth retardation due to impaired calcification of

bone epiphysis.

Frontal and parietal bossing

Rachitic Rosary beads due to Swelling of the costo-chondral junctions

Rachitic Rosary beads due to Swelling of the costo-chondral junctions

Harrison’s grooveLateral indentation of the chest wall at the site of attachment of diaphragm

Wrist enlargement

Wide ankle

(2). Extra – skeletal manifestations:

• HYPOTONIA AND DELAYED MOTOR DEVELOPMENT Muscle

weakness

• PROTUBERANT ABDOMEN, BONE PAIN, WADDLING GAIT

AND FATIGUE.

B. Investigations

* BASIC INVESTIGATIONS TO CONFIRM RICKETS:

• Serum Ca, P: Hypocalcemia if serum Calcium

less than 9 mg/dl

• X rays of ends of long bones at knees or wrists:

Widening and cupping of the distal ends of shaft.

Osteoporosis & Osteomalacia

Difference Between Osteoporosis & Osteomalacia

• Osteoporosis refers to the degeneration of already constructed bone, making them brittle, while osteomalacia is an abnormality in the building process of bone, making them soft.

Osteoporosis The word osteoporosis literally means porous bones . It

occurs when rate of degeneration of already constructed bone is rapid and exceed rate of bone building .

This leads to loss of an excessive amount of their protein and mineral content .

An osteoporotic bone characterized by:– Thinning of bone trabecula– low bone mass and volume.– Enhanced bone fragility and increase in fracture risk even

with any trivial trauma.

Osteoporotic Vertebra

* Types of osteoporosis:

A. Idiopathic type: - which is subclassified into

Post menopause (Type I).Senile type (Type II).

B. Secondary type: which occur secondary to any other disease, or drug intake .

Idiopathic Osteoporosis:

• Postmenopausal osteoporosis (type I)– Caused by lack of estrogen.– Estrogen loss triggers increases in InterLeukin-1, IL-6, and

Tumor Necrosis factor lead to increased osteoclast development and lifespan.

– Also estrogen loss stimulate parathormone hormone.

• Senile osteoporosis (type II): as a result of aging

Normal vs. Osteoporotic Bone

Commonest sites affected by osteoporosis

Osteoporosis in vertebra

Investigations:

- The primary method of testing is DEXA or dual energy

X-ray absorptiometry ,This can detect the density of

bones.

- Sometimes, ultrasound or CT scans are also used to

make a diagnosis.