Question

describe the effect of each of the following conditions on serum calcium levels and on bone density:

a) hyperparathyroidism
b) renal failure
c) very large intake of Vitamine D

Answer 1

Ans) a) When blood-calcium levels are too high, the parathyroid glands produce less PTH. But sometimes one or more of these glands produce too much hormone, leading to abnormally high levels ofcalcium (hypercalcemia) and low levels of phosphorus in your blood.

Parathyroid hormone (PTH) is associated with anabolic and catabolic skeletal effects that vary according to the kinetics of serum levels and the type of bone. The anabolic effects are manifested in patients with a periodic rapid transient rise in serum PTH, as seen with daily subcutaneous injection of PTH(1-34) and PTH(1-84) in the treatment of osteoporosis. These patients have an increase in bone mineral density (BMD), particularly at skeletal sites with a high trabecular component, such as the lumbar spine, and a reduction in fracture risk. The catabolic effects are typified in patients with primary hyperparathyroidism (PHPT) who have chronic persistently elevated PTH levels. Patients with long-standing PHPT have a reduction in BMD, particularly at predominately cortical skeletal sites, such as the one-third radius, with relative preservation of BMD at the lumbar spine. Some but not all studies have reported an increase in fracture risk with PHPT. Because many patients with PHPT are postmenopausal women at risk for osteoporosis owing to estrogen deficiency, BMD and fracture risk may be a result of multiple factors with variable effects on bone remodeling. The skeletal effects of normocalcemic PHPT have not yet been fully characterized, but may not be the same as hypercalcemic PHPT.

b) Renal failure:

Chronic kidney disease (CKD) causes imbalances in bone metabolism and increases the risk of a type of bone disease called renal osteodystrophy. These imbalances also can cause calcium to deposit in the blood vessels and contribute to heart disease. If calcium levels are low, a calciumsupplement may be prescribed.

In addition to harming bones, mineral and bone disorder in CKD can cause problems in the heart and blood vessels: High levels of blood calcium can damage blood vessels and lead to heart problems. High phosphorus levels also can cause blood vessels to become like bone, leading to hardening of the arteries.

c) Very large intake of Vitamine D:

- Vitamin D is involved in calcium absorption, immune function and protecting bone, muscle and heart health.

- However, taking extremely high doses of vitamin D3 for long periods of time may lead to excessive buildup in the body. Vitamin D intoxication occurs when blood levels rise above 150 ng/ml (375 nmol/l).

- Calcium supplements on their own have minimal effect on bone mineral density and fracture, and may increase the risk of cardiovascular disease," Avenell said. The only evidence that calcium and vitamin D together prevent fractures comes from a trial of older people with very low vitamin D levels in nursing homes.