From the Research
Osteomalacia causes low serum calcium, low phosphorus, elevated alkaline phosphatase (ALP), and elevated parathyroid hormone (PTH) levels due to vitamin D deficiency or resistance, as supported by the most recent and highest quality study available 1.
Pathophysiology of Osteomalacia
The pathophysiology of osteomalacia involves the inadequate mineralization of bone due to a deficiency in vitamin D, which is essential for calcium and phosphorus absorption from the intestines. When vitamin D is insufficient, calcium absorption decreases, leading to low serum calcium levels. This hypocalcemia triggers increased PTH secretion (secondary hyperparathyroidism) as the body attempts to normalize calcium levels. Elevated PTH increases calcium resorption from bone and promotes phosphorus excretion through the kidneys, resulting in hypophosphatemia. The body responds to inadequate bone mineralization by increasing osteoblast activity, which elevates alkaline phosphatase levels. This enzyme is produced during bone formation and is a marker of increased bone turnover.
Clinical Presentation and Diagnosis
Patients with osteomalacia may present with symptoms such as bone pain, muscle weakness, and increased risk of fractures. Laboratory findings typically include low serum calcium and phosphorus levels, elevated alkaline phosphatase, and elevated parathyroid hormone levels. Diagnosis is often confirmed by bone biopsy, which shows evidence of inadequate mineralization.
Treatment and Management
Treatment of osteomalacia involves vitamin D supplementation, typically 50,000 IU weekly for 8-12 weeks, then maintenance doses of 800-1000 IU daily, as well as calcium supplementation, 1000-1500 mg daily 2. It is also important to address any underlying causes of vitamin D deficiency, such as limited sun exposure or inadequate dietary intake. Patients should be encouraged to increase sun exposure and consume vitamin D-rich foods like fatty fish, egg yolks, and fortified dairy products to help maintain normal mineral homeostasis and prevent recurrence.
Key Points
- Osteomalacia is caused by vitamin D deficiency or resistance
- Vitamin D is essential for calcium and phosphorus absorption
- Treatment involves vitamin D and calcium supplementation, as well as addressing underlying causes
- Patients should be encouraged to increase sun exposure and consume vitamin D-rich foods to prevent recurrence
- The most recent and highest quality study available supports the use of vitamin D supplementation in the treatment of osteomalacia 1