Metabolic bone disease Flashcards
Recommended calcium intake
- Adult:1000 mg/day
- Pregnancy,lactation,postmenopausal:1.3g/day
- Children (1-18 yrs):0.5-1.3 g/day
- Infant (
vitamin D source and recommended daily intake
Sources of vitamin D? •Diet •UV light exposure on precursor in skin •Daily requirement? •400 International units
Epidemiology of metabolic bone disease
- 75 million people in the United States, Europe and Japan, including one third of postmenopausal women and most of the elderly.
- Results in more than 1.3 million fractures annually in the United States.
- Characterised by microarchitectural deterioration of bone tissue leading to decreased bone mass and bone fragility.
reduced bone mass is the result of
- hormone deficiencies,
- inadequate nutrition,
- decreased physical activity,
- comorbidity and
- the effects of medications.
fractures
- Fractures are more common in whites and Asians than in Africans and Hispanics, and are more common in women than in men.
- One possible reason is that Africans and men achieve higher peak bone densities than caucasians and women.
- With respect to women, age-related bone loss accelerates during menopause as estrogen levels decrease.
common fracture sites for metabolic bone disease
hip
vertebrae
wrist
primary osteoporosis vs secondary osteoporosis
Primary osteoporosis
•deterioration of bone mass that is unassociated with other chronic illness
•is related to aging and decreased gonadal function.
Secondary osteoporosis
•Results from chronic conditions that contribute significantly to accelerated bone loss. These chronic conditions include endogenous and exogenous thyroxine excess, hyperparathyroidism, malignancies, gastrointestinal diseases, medications, renal failure and connective tissue diseases.
nutrition as a risk factor for osteoporosis
- Because other nutrients besides calcium are essential for bone health, calcium alone may be insufficient to combat osteoporosis.
- Phosphorus is a substantial component of carbonated drinks, and high intake compromises calcium uptake by bone.
- Eating disorders also affect bone mineral density.
- Inability to maintain normal body mass promotes bone loss
- The body weight history of women with anorexia nervosa is the most important predictor of the presence of osteoporosis.
- Major demands are placed on the mother by the fetus for calcium during pregnancy and by the infant during lactation.
Diagnosis of osteoporosis
HISTORY AND PHYSICAL EXAMINATION
•Those affected by complications of osteoporosis may complain of upper- or mid/thoracic back pain associated with activity, aggravated by long periods of sitting or standing, and relieved by rest
•The history should also assess the likelihood of fracture: low bone density, a propensity to fall, and prior fractures are indications of increased fracture risk.
•Common fracture sites are the vertebrae, forearm, femoral neck and proximal humerus.
Osteomalacia (rickets) definition
Generalized bone condition in which there is inadequate mineralization of the bone.
•Signs and symptoms overlap with osteoporosis but the two diseases are different.
•There are two main causes of osteomalacia:
•insufficient calcium absorption from the intestine because of lack of dietary calcium or a deficiency of or resistance to the action of vitamin D; and
•Phosphate deficiency caused by increased renal losses.
Diagnosis of osteomalacia (rickets)
- Osteomalacia in adults starts insidiously as aches and pains in the lumbar region and thighs, spreading later to the arms and ribs.
- The pain is symmetrical, non-radiating and is accompanied by sensitivity in the involved bones.
- There is often associated proximal muscle weakness.
- The patient may develop a kyphoscoliosis in the thoracic and lumbar spine regions.
- Pathologic fractures due to weight bearing may develop.
- Adults with a past history of rickets may be short stature, have bowing of the lower limbs and enlarged costochondaral junctions.
Laboratory assessments for osteomalacia (rickets)
- Serum calcium is low
- Serum Phosphate is low
- Serum Vitamin D is low
- Urine calcium concentration is low
- Alkaline phosphotase is raised
- Parathyroid hormone is raised
Hyperparathyroidism- definition
- The effects of parathyroid hormone on serum calcium are mediated by increasing renal tubular resorption of calcium, increasing calcium absorption from the intestines (via vitamin D) and increasing release of calcium from bone.
- 85% of hyperparathyroidism is the result of an adenoma in a single parathyroid gland.
- Hypertrophy of all four parathyroid glands causes hyperparathyroidism in 15 percent of patients.
- A very small number of cases of hyperparathyroidism result from parathyroid malignancies.
Hyperparathyroidism- diagnosis
Some combination of headaches, fatigue, anorexia, nausea, paresthesias, muscular weakness, pain in the extremities, pain in the abdomen and other nonspecific symptoms appears to be the most common presentation of primary hyperparathyroidism.
•Elevated levels of calcium and parathyroid hormone confirm the diagnosis.
Indications for screening loss of bone
- Concerned perimenopausal woman willing to start drug therapy
- Radiographic evidence of bone loss
- Patient on long-term glucocorticoid therapy
- Asymptomatic hyperparathyroidism
- Monitoring therapeutic response in women undergoing treatment for osteoporosis
