What is the main cause of osteomalacia in adults?

Vitamin D deficiency is the primary cause of osteomalacia in adults. Osteomalacia is characterized by the softening of bones due to the improper mineralization of osteoid, which is the unmineralized organic matrix of bone. Vitamin D plays a crucial role in bone health by facilitating the absorption of calcium and phosphate from the diet, both of which are essential for maintaining healthy bone mineralization.

When there is insufficient vitamin D, which can occur due to factors such as lack of sunlight exposure, limited dietary intake, or certain medical conditions affecting absorption, the body is unable to effectively absorb the necessary minerals. This deficiency leads to a decrease in bone mineral density and can cause symptoms such as bone pain and an increased risk of fractures, which are characteristic of osteomalacia.

In contrast, excess calcium intake, dehydration, and bone overexertion do not directly cause osteomalacia. Excessive calcium may lead to different complications, dehydration affects overall health but not specifically bone mineralization, and overexertion of bones primarily pertains to stress fractures rather than the softening associated with osteomalacia. Thus, understanding the fundamental role of vitamin D in bone health is key to comprehending the pathophysiology of osteomalacia.