Three USMLE Step 1 questions covering glucocorticoid-induced osteoporosis, breast lesions that raise cancer risk, and spinal deformities. Pick your answer first, then open the explanation.
Question 1: Why do corticosteroids cause osteoporosis?
Which of the following is one of the reasons that corticosteroid therapy may lead to osteoporosis?
A. Corticosteroids decrease renal phosphate excretion B. Corticosteroids decrease intestinal calcium absorption C. Corticosteroids increase osteoblast mRNA production D. Corticosteroids increase osteoblast protein synthesis
Correct answer: B. Corticosteroids decrease intestinal calcium absorption
Glucocorticoids decrease intestinal calcium absorption and increase urinary calcium loss. Their most important effect on bone is direct: they inhibit osteoblasts (less bone formation) and increase osteoclast activity (more bone resorption).
Why the other options are wrong:
A is not a recognized mechanism of steroid-induced bone loss.
C and D are the opposite of what happens: corticosteroids suppress osteoblast gene expression and protein (collagen) synthesis.
High-yield: Glucocorticoids are the most common cause of secondary osteoporosis. Patients on long-term steroids (≥3 months) should receive calcium, vitamin D and often a bisphosphonate.
Question 2: Which breast biopsy finding increases cancer risk?
A middle-aged woman complains of a lump in her left breast. A biopsy is performed. Which of the following microscopic findings is most likely associated with an increased risk of developing carcinoma?
A. Apocrine metaplasia B. Atypical ductal hyperplasia C. Multiple cystic spaces D. Sclerosing adenosis
Correct answer: B. Atypical ductal hyperplasia
Atypical ductal hyperplasia (and atypical lobular hyperplasia) is a proliferative lesion with atypia that increases the risk of invasive breast carcinoma about 4–5 times.
Why the other options are wrong:
Apocrine metaplasia and cysts are non-proliferative fibrocystic changes with no increased risk.
Sclerosing adenosis is a proliferative lesion without atypia; the risk increase is only slight (about 1.5–2 times).
High-yield: Breast cancer risk ladder: non-proliferative (no risk) → proliferative without atypia (slight) → atypical hyperplasia (moderate) → carcinoma in situ (high).
Question 3: What causes lateral curvature of the spine in a teenage girl?
A 14-year-old girl is brought in because of a twisted appearance of her back for the past 2 years. X-ray shows a lateral curvature of the mid-thoracic spine. Which of the following is the most likely diagnosis?
A. Kyphosis B. Lordosis C. Osteoporosis D. Scoliosis
Correct answer: D. Scoliosis
Scoliosis is a lateral (side-to-side) curvature of the spine, usually with vertebral rotation. The most common type is adolescent idiopathic scoliosis, which is more often progressive in girls during the growth spurt.
Why the other options are wrong:
Kyphosis is an exaggerated forward (anterior-posterior) rounding of the thoracic spine (“hunchback”).
Lordosis is an exaggerated inward curve of the lumbar spine (“swayback”).
Osteoporosis is low bone mass; it is rare in a healthy teenager and does not cause lateral curvature.
High-yield: Screening sign: asymmetry of the back on the Adams forward bend test. Scoliosis is also seen in Marfan syndrome, neurofibromatosis and Duchenne/Friedreich disorders.
Key takeaways
Glucocorticoids → osteoporosis by inhibiting osteoblasts and reducing calcium absorption.
Atypical ductal/lobular hyperplasia → increased breast cancer risk.
Lateral spine curvature in an adolescent girl → idiopathic scoliosis.
