Biochemical marker of bone turnover

Osteocalcin is a marker of bone formation.

It is produced by osteoblasts.

Osteocalcin, is a noncollagenous protein hormone found in bone and dentin.

Gene location is Chromosome 1.

Its synthesis is vitamin K dependent.

In humans, osteocalcin is encoded by the BGLAP gene.

Involved in the process of mineralization rather than matrix production.

Plasma concentrations are markers of bone formation, and circulating concentrations correlate well with histological measures of bone formation rate.

It plays a role in the body’s metabolic regulation.

Osteocalcin acts on beta cells in the pancreas to increase insulin.

Osteocalcin in fat cells triggers the release of the hormone adiponectin, which increases sensitivity to insulin.

Osteocalcin acts on myocytes to promote energy availability and utilization and in this manner favors exercise capacity.

It concentrates in bone, but it does not play an important role in bone mineralization.

Osteocalcin, in its uncarboxylated form acts as a hormone in the body, signalling in the pancreas, fat, muscle, testes, and brain.

Osteocalcin acts on Leydig cells of the testes, stimulating testosterone biosynthesis and therefore affect male fertility.

Osteocalcin plays an important role in development and functioning of the brain.

The fight or flight response stimulates osteocalcin release from bone within minutes.

It is often used as a marker for the bone formation process, and higher serum osteocalcin levels are correlated with increases in bone mineral density during treatment with anabolic bone formation drugs for osteoporosis, such as teriparatide.

Around 25% of circulating osteocalcin consists of intact osteocalcin, the remaining immunoreactivity comprising variousl terminal fragments.

When bone is resorbed, osteocalcin fragments are released, and are reflected in plasma concentrations.

Osteocalcin fragments are cleared predominantly by the kidneys, so there is considerable immunological heterogeneity in plasma osteocalcin in patients with renal impairment that limits the usefulness of osteocalcin as a marker of bone formation.

It has greater sensitivity than alkaline phosphatase in the detection of low rates of bone formation.

There is a two-fold rise in plasma osteocalcin concentration at the menopause, and levels fall markedly during pregnancy.

Cord blood concentrations are two to three times higher than adult values.

Osteocalcin half-life in the circulation is about 5 min.

Plasma osteocalcin concentrations exhibit a diurnal variation.

Plasma osteocalcin levels peak in the early morning being about 15% higher than the nadir value, which occurs in the afternoon.

Plasma osteocalcin conncentrations may be depressed by about 10% by alcohol intake.

Plasma osteocalcin conncentrations may be depressed by about 50% by glucocorticoids.

Plasma concentrations rise when osteoblasts are stimulated by the administration of 1,25(OH)2D.

It contributes to the regulation of blood sugar and fat deposition.

Increases both the insulin secretion and sensitivity, in addition to boosting the number of insulin-producing cells and reducing stores of fat.

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