A 48-year-old woman comes to the emergency department due to back pain after minor trauma. She has no leg weakness or numbness. Review of systems is positive for recent-onset hot flashes and irregular menses; her most recent menstruation was 2 weeks ago. The patient has a long history of hypothyroidism treated with levothyroxine and rheumatoid arthritis treated with methotrexate. She has also taken oral prednisone for frequent symptom flares. The patient does not use tobacco, alcohol, or illicit drugs, and she consumes a balanced diet. Physical examination shows point tenderness over the midthoracic spine. The straight-leg raising test is negative, and neurologic examination of the lower extremities shows no abnormalities. Spine imaging is shown below:
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Which of the following contributed most to this patient's current condition?
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This patient has a fragility fracture of a thoracic vertebra (ie, fracture due to a force significantly less than that required to fracture a normal bone). A fragility fracture suggests underlying bone pathology, often due to metastatic malignancy or intrinsic bone disease. In this patient, who has had frequent exposure to systemic glucocorticoids (eg, prednisone), this likely represents osteoporosis.
Chronic or recurrent glucocorticoid use, as is occasionally needed for patients with rheumatoid arthritis, is associated with an increased risk for osteoporosis. Osteoporosis can also occur due to systemic absorption of topical glucocorticoids (eg, inhaled glucocorticoids used in the treatment of asthma). Glucocorticoids promote osteoporosis by inhibiting proliferation and differentiation of osteoblast precursor cells, promoting osteoclast differentiation and activity, and suppressing intestinal calcium absorption and renal calcium reabsorption.
(Choice A) Thyroid hormone stimulates osteoclast differentiation and activity, bone resorption, and release of calcium into circulation. Thyrotoxic states (eg, excessive levothyroxine dose, endogenous hyperthyroidism) cause increased bone turnover with net bone loss. However, inadequate levothyroxine dosing is not a significant contributor to bone loss.
(Choice C) Deficiency of vitamin D can lead to osteoporosis. Risk factors include malabsorption syndromes (eg, celiac disease) and lack of sun exposure, but nutritional deficiency is not a common cause of vitamin D deficiency. Glucocorticoid use is likely a more significant factor in this patient.
(Choice D) Loss of ovarian estrogen production after menopause leads to an increased risk of osteoporosis. However, postmenopausal osteoporosis develops slowly, and fracture is uncommon until at least 10-15 years after cessation of menses; this patient is still perimenopausal, and loss of estrogen is unlikely to have caused her osteoporosis.
(Choice E) Involvement of the cervical spine is common in rheumatoid arthritis and, over time, can lead to atlantoaxial instability, subluxation with possible cord compression, and odontoid fracture. However, involvement of the thoracic and lumbar spine is uncommon.
Educational objective:
Osteoporosis is a common cause of fragility fractures, which occur in the absence of significant trauma. Chronic or recurrent use of glucocorticoids (eg, prednisone) promotes osteoporosis and increases the risk of fractures.