An Athletic Teen Suddenly Prone to Falls and Fractures

Inas H. Thomas, MD


June 06, 2022

This patient's type 1 diabetes may contribute to low bone mineral density, which can increase his risk for fractures and also affect his ability to absorb vitamin D from his diet. However, his low vitamin D level needed to be addressed first. In the United States, vitamin D deficiency is prevalent, with different studies citing between 40% and 50% of teens as having vitamin D deficiency or insufficiency.[5] Many factors lead to vitamin D deficiency, including a change in diet (consuming less vitamin D-fortified milk), reduced time outdoors, and sun protection.[5] Medications such as antiseizure drugs and glucocorticoids can affect the metabolism of vitamin D, leading to increased requirements. Other disorders that can affect absorption of vitamin D, such as cystic fibrosis and Crohn disease, can also result in rickets due to vitamin D deficiency.[6]

The exact value that determines whether a patient is vitamin D sufficient is highly debated; most experts believe that a 25-hydroxy vitamin D level greater than 30-32 ng/mL excludes clinically significant deficiency.[6,7] PTH levels rise when 25-hydroxy vitamin D levels are below 20 ng/mL and stabilize when the level is more than 30 ng/mL.[8] Secondary hyperparathyroidism contributes to decreased bone mineral density by releasing calcium from the skeleton in order to maintain normal serum calcium levels. Phosphorus is also released and excreted in the urine, which may result in low or low-normal serum phosphorus levels. With the change in the calcium-phosphorus balance, mineralization is affected, which changes the architecture of the bones. This eventually may lead to small areas in the skeleton that are more fragile and at risk for fractures.[5]

Not only is vitamin D critical for maintaining adequate calcium and phosphorus levels and bone health, but it also may have other subtle roles. Vitamin D is known to affect the T lymphocytes and B lymphocytes in the immune system.[9] With that knowledge, studies are underway to assess how vitamin D affects certain autoimmune diseases such as type 1 diabetes and multiple sclerosis. Topical vitamin D medications are used to treat psoriasis because keratinocytes have vitamin D receptors. Additional studies are investigating the interaction of vitamin D on various cancers, mental health, and development.[9]


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