Osteocalcin

Are you being treated for osteoporosis and wondering whether treatment is working, or does your doctor suspect increased bone turnover? Osteocalcin is a protein produced by bone-building cells, so its blood level shows how active bone formation is. The test does not measure bone density and does not on its own diagnose osteoporosis.

Who the test is intended for

• people being treated for osteoporosis, when the doctor wants to monitor treatment effects alongside bone density measurement;
• postmenopausal women at increased risk of osteoporosis, as additional information in a doctor-led investigation;
• when diseases with increased bone turnover are suspected, such as Paget’s disease or overactivity of the parathyroid or thyroid glands;
• people taking corticosteroids long-term, which slow bone formation;
• when osteomalacia or pronounced vitamin D deficiency is suspected, alongside other bone metabolism tests.

What the test reveals

Bone is constantly broken down and rebuilt throughout life. Osteocalcin is produced by osteoblasts, the cells that build new bone, and some enters the blood. When bone turnover is faster, for example after menopause, blood osteocalcin is usually higher.

These tests are called bone turnover markers. They do not show how strong bone is, but how quickly it changes. Osteoporosis is diagnosed by bone density measurement (densitometry), for which a doctor refers you, while osteocalcin helps monitor how bone responds to treatment. Similar information about bone formation is provided by bone alkaline phosphatase, while changes with age are described in the article about menopause and other “pauses”.

What the test involves and how to prepare

Blood is taken from a vein in the arm, and the whole procedure takes a few minutes. It is best to come in the morning because osteocalcin levels vary during the day. Fasting is not essential unless glucose, lipids or PT are measured from the same blood collection. Have follow-up collections at the same time of day and, if possible, in the same laboratory, because results from different methods cannot be compared directly.

• State if you have recently had a fracture, because bone healing temporarily raises osteocalcin.
• State whether you take corticosteroids or osteoporosis medicines and whether you have kidney disease. If you take biotin (for example, hair and nail supplements), state this at blood collection.

What your result means

The reference range depends on age, sex and method and is printed on the report. In children and adolescents, values are physiologically higher because their bones are growing. The doctor interprets the report, most often alongside calcium, vitamin D, PTH and the bone density result.

• Elevated osteocalcin means increased bone turnover. It is expected during growth and fracture healing and is also found after menopause, in Paget’s disease, overactivity of the parathyroid or thyroid glands and bone metastases. In impaired kidney function, it is also higher because it is excreted more slowly.
• Low osteocalcin means slowed bone formation, for example with corticosteroids or an underactive parathyroid or thyroid gland. During treatment with medicines that slow bone breakdown, a fall in values usually shows that treatment is working.
• Normal osteocalcin does not rule out osteoporosis, because turnover is often only slightly altered in this disease.

How to arrange testing

You can have blood collected without an appointment or referral at one of our branches across Croatia (listed on the Contact page). Prices for all tests and panels are available in the price list.

Frequently asked questions

Can osteocalcin show whether I have osteoporosis?

No. Osteoporosis is diagnosed by bone density measurement. Osteocalcin shows how active bone turnover is and is used mainly to monitor treatment.

Why is it best to come in the morning?

Osteocalcin levels change during the day. When blood is always collected at a similar time and under the same conditions, reports are comparable and the doctor can assess changes more easily.

When is the test repeated during osteoporosis treatment?

It is usually performed before starting treatment and again after several months to see whether bone is responding to treatment. The doctor will determine the exact follow-up schedule.

Which tests are performed alongside osteocalcin?

Most often calcium, phosphorus, vitamin D and PTH, which provide an overall picture of bone metabolism, and bone alkaline phosphatase if needed. The doctor decides which you need.