Decreased exposure of the skin to sunlight is a common cause of<unk> . People with a darker skin pigment with increased amounts of melanin may have decreased production of vitamin D. Melanin absorbs ultraviolet B radiation from the sun and reduces vitamin D production. Sunscreen can also reduce vitamin D production. Medications may speed up the metabolism of vitamin D, causing a deficiency. The liver is required to transform vitamin D into 25-hydroxyvitamin D. This is an inactive metabolite of vitamin D but is a necessary precursor (building block) to create the active form of vitamin D. The kidneys are responsible for converting 25-hydroxyvitamin D to 1,25-hydroxyvitamin D. This is the active form of vitamin D in the body. Kidney disease reduces 1,25-hydroxyvitamin D formation, leading to a deficiency of the effects of vitamin D. Intestinal conditions that result in malabsorption of nutrients may also contribute to<unk>  by decreasing the amount of vitamin D absorbed via diet. In addition, a<unk>  may lead to decreased absorption of calcium by the intestines, resulting in increased production of osteoclasts that may break down a person's bone matrix. In states of hypocalcemia, calcium will leave the bones and may give rise to secondary hyperparathyroidism, which is a response by the body to increase serum calcium levels. The body does this by increasing uptake of calcium by the kidneys and continuing to take calcium away from the bones. If prolonged, this may lead to osteoporosis in adults and rickets in children.
Vitamin D deficiency
Vitamin D toxicity
Endocrine bone disease
Metabolic bone disease
Disorders of calcium metabolism
Steroid-induced osteoporosis
Molybdenum deficiency
Mineral deficiency