Osteoporosis

Osteoporosis refers to the decreased bone density, which increases the risk for fractures. It’s defined according to the results of a DEXA (dual-energy x-ray absorptiometry) scan or by the presence of a pathological fracture. The DEXA scan calculates the bone mineral density and gives a T-score. Osteoporosis is defined as a T-score of less than -2,5 standard deviations. This means that a person with osteoporosis has 2,5 standard deviations lower bone density than an average young adult female.

T-score between -1 and -2,5 is less severe and is called osteopaenia.

Etiology

• Female gender
• Old age
• Smoking
• Low calcium intake
• Low vitamin D intake
• Low levels of physical exercise
• Alcohol consumption

Osteoporosis can also be secondary to:

• Glucocorticoids
• PPIs
• Hyperthyroidism
• Chronic kidney disease

Clinical features

Most patients with osteoporosis are asymptomatic, but the condition predisposes to so-called pathological fractures. These are fractures which are caused by normal activities which would otherwise not cause fracture in healthy people. Fractures can occur during bending over, sneezing, or falling from small height. These fractures most commonly affect the vertebrae.

Vertebral compression fractures can occur in the absence of trauma. These are often asymptomatic but lead to decreased height and increased kyphosis over time.

Diagnosis and evaluation

Even though osteoporosis is defined based on the DEXA scan, it can be diagnosed in patient with risk factors who present with pathological fractures. In the absence of pathological fractures, a DEXA scan is required for diagnosis. Even though the pathological fracture is enough to make the diagnosis, a DEXA scan of these patients is usually performed anyway as part of the evaluation.

Some countries recommend screening for osteoporosis in persons at risk, like postmenopausal persons above a certain age, or patients on long-term glucocorticoid therapy. In other countries (like Norway) patients are only evaluated after a pathological fracture has occurred.

Biochemical bone markers

Multiple markers can be measured in the blood which reflect bone metabolism. Osteocalcin, bone-specific alkaline phosphate, and N-terminal propeptide type 1 collagen (P1NP) are markers of bone formation, while C-terminal telopeptide type 1 collagen (CTX-1) is a marker of bone resorption. They can be measured in the urine, but serum measurement is more convenient. These markers are mostly used to evaluate treatment response.

Treatment

Bisphosphonates like alendronate and risedronate are the first-line drugs in the treatment and is recommended for all patients with osteoporosis. To prevent these drugs from causing esophagitis they should be taken at least 30 minutes before meals, with plenty of water, and the patient should not lie down for 30 minutes after.

Second-line drugs include teriparatide (PTH analogue), raloxifene and denosumab (anti-RANKL).