MCQs – Metabolic 3

Modern Study Review (AI-Generated)

High-Yield Summary

This topic is a staple of the Royal College exam, focusing heavily on metabolic bone diseases and their radiographic and biochemical hallmarks. The single most important clinical trade-off is distinguishing osteomalacia from osteoporosis, primarily based on serum and urine biochemical abnormalities versus biopsy findings. The examiner often forces a choice between recognizing classic radiographic signs (e.g., Looser’s lines) and interpreting lab values (alkaline phosphatase, calcium, phosphate). While the exam favors classic textbook presentations, modern practice increasingly integrates advanced imaging and biochemical panels for early diagnosis and management.

High-Yield Decision Matrix

Active Recall Q&A

Q: What are the characteristic x-ray findings in patients with rickets?
A: Widened physis, irregular or cupped epiphyseal line, indistinct or absent zone of provisional calcification.
Related Pearl: The zone of provisional calcification normally appears as a thin, dense white line; its loss indicates defective mineralization, a key diagnostic clue.

Q: What is the most significant bone change seen in children with rickets?
A: Presence of Looser’s lines, representing unmineralized osteoid.
Related Pearl: Looser’s lines are pseudofractures and a hallmark of defective bone mineralization, often confused with stress fractures.

Q: What are the signs of vitamin D intoxication?
A: Hypercalcemia, hypercalciuria, and increased or normal alkaline phosphatase levels.
Related Pearl: Vitamin D toxicity leads to hypercalcemia, which can cause nephrocalcinosis and renal impairment if untreated.

Q: What is the most common cause of primary hyperparathyroidism?
A: A single parathyroid adenoma in 80% of cases.
Related Pearl: Surgical excision of the adenoma is curative in most cases, emphasizing the importance of accurate localization.

Q: What is the initial treatment for hypercalcemia?
A: Saline infusion combined with furosemide (Lasix).
Related Pearl: Volume expansion promotes renal calcium excretion; loop diuretics inhibit calcium reabsorption in the thick ascending limb of Henle.

Q: What laboratory and clinical features characterize osteomalacia?
A: Increased alkaline phosphatase, muscle weakness, skeletal changes, and presence of Looser’s lines.
Related Pearl: Osteomalacia results from defective bone mineralization in adults, commonly due to vitamin D deficiency or malabsorption.

Q: What is the radiographic hallmark of osteomalacia?
A: Looser’s lines (pseudofractures).
Related Pearl: These lines represent areas of incomplete fracture due to poor mineralization and are pathognomonic.

Q: How can osteoporosis be distinguished from osteomalacia?
A: Osteoporosis shows no urine or serum abnormalities; osteomalacia shows low serum calcium and phosphate, low urine calcium, and high alkaline phosphatase; biopsy may be required.
Related Pearl: Osteoporosis is a disorder of bone quantity; osteomalacia is a disorder of bone quality/mineralization, which affects treatment decisions.

Q: Does hemophilia cause secondary gout?
A: No, hemophilia does not cause secondary gout.
Related Pearl: Hemophilia causes hemarthrosis but not crystal-induced arthritis; this distinction is critical in differential diagnosis of joint pain.

Q: In which conditions is serum alkaline phosphatase elevated?
A: Osteomalacia, myositis ossificans, Paget’s disease, and osteogenesis imperfecta.
Related Pearl: Elevated alkaline phosphatase reflects increased osteoblastic activity or bone turnover, useful in monitoring disease activity.

Q: When are CPK levels increased?
A: In Duchenne muscular dystrophy and congenital myopathy.
Related Pearl: Elevated CPK indicates muscle membrane damage or necrosis, aiding in diagnosis and disease monitoring.

Q: What are the pediatric clinical features of hypothyroidism?
A: Neonatal cretinism, child appears younger than chronological age, delayed puberty, growth retardation, and late or fragmented secondary ossification centers (especially bilateral femoral epiphysis).
Related Pearl: Fragmented femoral epiphyses in a child with growth delay should prompt evaluation for hypothyroidism, as early treatment prevents irreversible deficits.

Classic Clinical Notes

• The x-ray findings of patients with rickets: widened physis. The epiphyseal line is irregular, cupped, or widened. The zone of provisional calcification, which is ordinarily a thin dense white line on x-rays, appears indistinct or absent. In children with rickets, the most significant finding among the bone changes is the presence of Looser’s lines (unmineralized osteoid).

• Signs of vitamin D intoxication: hypercalcemia, hypercalciuria, increased or normal alk phos.

• Most common cause of primary hyperPTH is a single adenoma (80%).

• Initial treatment of hypercalcemia is saline infusion with lasix.

• Osteomalacia tends to have an increased alk phos, muscle weakness, skeletal changes, and Looser’s lines.

• The radiographic hallmark of osteomalacia is Looser’s lines.

• Distinguishing osteoporosis from osteomalacia – may require biopsy. Typically, there are no urine or serum abnormalities in osteoporosis. In osteomalacia, the serum calcium and phosphate may be low. Urine calcium is low. Alkaline phosphate is high.

• Hemophilia does not cause secondary gout.

• Serum alk phos is high in osteomalacia, myositis ossificans, paget’s, and osteogenesis imperfecta.

• CPK levels are increased in Duchenne MD and congenital myopathy.

• Hypothyroidism is associated with cretinism (as a neonate), the child looks younger than chronologic age (hence puberty is delayed – they do not get precocious puberty!), growth is retarded, and secondary centers of ossification form late and may show fragmentation (beware of this diagnosis when bilateral femoral epiphysis look fragmented).

Last Updated on January 25, 2026 by Christian Veillette