What does a low T score indicate and how is it treated in osteoporosis?

From the Guidelines

A low T score indicates decreased bone mineral density, with scores between -1 and -2.5 suggesting osteopenia and scores below -2.5 confirming osteoporosis, as defined by the World Health Organization (1).

Definition of Osteoporosis

Osteoporosis is a skeletal disorder characterized by compromised bone strength predisposing to an increased risk of fracture (1). The diagnosis of osteoporosis can be based on a history of fragility fracture or by measuring bone mineral density (BMD) by dual-energy x-ray absorptiometry (DXA) (1).

Treatment of Osteoporosis

Treatment for osteoporosis typically begins with lifestyle modifications including:

• Weight-bearing exercise
• Adequate calcium intake (1000-1200 mg daily)
• Vitamin D supplementation (800-1000 IU daily) First-line medication therapy usually involves bisphosphonates such as:
• Alendronate (70 mg weekly)
• Risedronate (35 mg weekly)
• Zoledronic acid (5 mg IV yearly) These medications work by inhibiting bone resorption by osteoclasts, thereby slowing bone loss (1). For those who cannot tolerate bisphosphonates, alternatives include:
• Denosumab (60 mg subcutaneously every 6 months), which inhibits RANK ligand to decrease osteoclast activity
• Anabolic agents like teriparatide or abaloparatide (both given as daily injections for up to 2 years) to stimulate new bone formation (1).

Monitoring and Follow-up

Treatment decisions should consider fracture risk, comorbidities, and potential side effects, with medication therapy typically continuing for 3-5 years before reassessment (1). Regular monitoring with follow-up bone density scans every 1-2 years helps evaluate treatment effectiveness (1).

Key Considerations

The World Health Organization (WHO) defines normal BMD as a T-score ≥ -1.0, low bone mass or osteopenia as a T-score between -1.0 and -2.5, and osteoporosis as a T-score ≤ -2.5 (1). The National Osteoporosis Foundation (NOF) recommends pharmacologic treatment for all postmenopausal women and men over age 50 years with a T-score ≤ -2.5 (1). In patients with low bone mass but T-scores greater than -2.5, a fracture risk assessment tool, such as FRAX, is used to determine the need for treatment (1).

From the FDA Drug Label

A two-year, double-blind, placebo-controlled, multicenter study of alendronate sodium 10 mg once daily enrolled a total of 241 men between the ages of 31 and 87 (mean, 63) All patients in the trial had either a BMD T-score less than or equal to -2 at the femoral neck and less than or equal to -1 at the lumbar spine, or a baseline osteoporotic fracture and a BMD T-score less than or equal to -1 at the femoral neck A one-year, double-blind, placebo-controlled, multicenter study of once weekly alendronate sodium 70 mg enrolled a total of 167 men between the ages of 38 and 91 (mean, 66) Patients in the study had either a BMD T-score less than or equal to -2 at the femoral neck and less than or equal to -1 at the lumbar spine, or a BMD T-score less than or equal to -2 at the lumbar spine and less than or equal to -1 at the femoral neck, or a baseline osteoporotic fracture and a BMD T-score less than or equal to -1 at the femoral neck

A low T score indicates osteoporosis or low bone mass. In the context of osteoporosis, a T score of:

• -1 to -2.5 indicates low bone mass (osteopenia)
• less than -2.5 indicates osteoporosis Treatment for osteoporosis with a low T score may involve medications such as alendronate sodium, which can help increase bone mass and reduce the risk of fractures. The treatment goal is to improve bone density and reduce the risk of osteoporotic fractures. 2

From the Research

Definition and Diagnosis of Osteoporosis

• Osteoporosis is a common condition characterized by low bone mineral density (BMD) and an increased risk of fragility fractures 3.
• The diagnosis of osteoporosis can be confirmed by DEXA (dual-energy X-ray absorptiometry) scan, which measures BMD at the lumbar spine, femoral neck, or total hip 3, 4.
• A T-score of -2.5 or lower at any of these sites is considered diagnostic of osteoporosis 3, 4.

Interpretation of T-Score

• A low T-score indicates a lower BMD compared to the average value for a healthy young adult 3, 5.
• The T-score is used to diagnose osteoporosis, but it has limitations, such as diagnostic misclassification when using multiple-site BMD measurements 5.
• The T-score should be considered in the context of other diagnostic aspects, such as family history, laboratory results, and genetic influences 6.

Treatment of Osteoporosis

• Oral bisphosphonates are the first-line treatment for osteoporosis 3.
• If bisphosphonates are contraindicated or not tolerated, parenteral therapy should be considered 3.
• Treatment should be considered in patients with a BMD T-score of -1.5 or lower, especially in those with a high risk of fracture 3, 7.
• Teriparatide has been shown to be effective in treating severe osteoporosis, with improvements in BMD and reduction in fracture risk 7.