Vitamin D Deficiency & Hyperparathyroidism In Pediatrics

Vitamin D, a fat-soluble vitamin, is synthesized in the skin and also absorbed from the intestines. Vitamin D is initially inactive, it then has to be processed by the body to be active. To absorb calcium, vitamin D is needed. Low vitamin D leads to poor calcium absorption; this results in low blood calcium. Low blood calcium stimulates the parathyroid gland to release parathyroid hormone. Neonates born to vitamin D deficient mothers also have elevated parathyroid hormone release.

Hyperparathyroidism in the Newborn

Mothers can become deficient in active vitamin D during pregnancy for several reasons such as inadequate exposure to sunlight, insufficient dietary intake of vitamin D or poor intestinal absorption of vitamin D. Low blood calcium results from lack of active vitamin D, or 25-hydroxyvitamin D, in the blood. In pregnancy, the fetus is entirely dependent on calcium that comes from the mother through the placenta; low calcium in the mother also cause low calcium in the fetus. The parathyroid gland of fetus is stimulated to increase production of parathyroid hormone due to low blood calcium; eventually parathyroid hormone becomes excessive in the blood. Excess parathyroid hormone in the blood is called hyperparathyroidism.

Complications

Low blood calcium is a problem for the heart which requires adequate calcium in blood to function properly. Low blood calcium causes an irregular pulse. Very low blood calcium is a potential cause of irreversible heart failure, according to Wily Online Library.

Increased secretion of parathyroid hormone from the parathyroid gland is a common effect of low blood calcium. Excess parathyroid hormone release causes excessive bone breakdown and weakening of the bone.

Low active vitamin D in newborn is also associated with recurrent lung infections.

Associated Symptoms

Low blood calcium causes tetany, a condition of uncontrollable muscle contractions. It causes strange sensations over the lips and tongue as well as abnormal twitching of the facial muscles.

Low blood calcium leads to weakening of the bones because calcium is needed to form a strong and healthy bone. Excessive parathyroid hormone released as a consequence of low blood calcium also weakens bone by stimulating the break down of bone in order to release calcium to blood. Symptoms experienced by children are more severe than in adults. There is bone and joint pain; other symptoms are generalized weakness, abdominal pain, nausea and vomiting. Increased frequency of urination is seen in children as well.

Diagnosis

Evaluation of vitamin D deficiency begins with the sampling of blood from a vein of the arm. The sample of blood is then taken to the lab and tested for levels of active vitamin D. A normal level of active vitamin D should be above 30 ng/mL; if less than 30 ng/mL, then it is abnormal. An active vitamin D level below 20 ng/mL is defined as vitamin D deficiency, according to Merck Manuals Online Medical Library.

Treatment

Hyperparathyroidism in neonates is a result of vitamin D deficiency in mother; in children, it's a result of poor dietary intake of vitamin D. A neonate with hyperparathyroidism will be low on both calcium and vitamin D. In neonates, vitamin D should be given at doses of 400 IU/day, with 500 mg of calcium per day in food. In older children and adults, the U.S. Department of Health and Human Services, recommends the supplementation of vitamin D at doses of 700 to 800 IU/day with 500 to 1,200 mg of calcium; this is effective in preventing loss of bone density.

Dietary modifications including the intake of fish, eggs, vitamin D-fortified milk and cod liver oil, should be considered since these foods are abundant sources of vitamin D.