Hormones and minerals play an important role in maintaining your bone density. Healthy bones continuously rebuild, sometimes taking a slightly altered shape or structure. To grow and rebuild, bones need:
- the hormone calcitriol—the active form of vitamin D produced by the kidney
- calcium
- phosphorus
- parathyroid hormone
The kidneys play an important role in maintaining bone mass and structure by balancing phosphorus and calcium levels in the blood. The kidney activates Vitamin D3 consumed from food, turning it into calcitriol, the active form of the vitamin. Calcitriol helps the kidneys maintain blood calcium levels and promotes the formation of bone. Calcitriol also acts directly on the parathyroid glands by suppressing the secretion of parathyroid hormone (PTH). Deficiency of the active form of Vitamin D is common in CKD and supplementation is recommended on confirmed deficiency. Supplementation of active Vitamin D helps increase calcium absorption from the small intestine.
The kidneys also clears extra phosphate, helping balance phosphate and calcium levels in the blood. Keeping the proper level of phosphate in the blood helps maintain bone density. Early intervention to prevent an increase in phosphate levels includes dietary adjustment and prescription of phosphate binding medication.
The parathyroid glands, four pea-sized glands in the neck, produce parathyroid hormone, or PTH. Parathyroid hormone plays an important role in controlling calcium levels in the blood. In patients with chronic kidney disease (CKD), extra parathyroid hormone (termed hyperparathyroidism) is released into the blood to move calcium from the bones into the bloodstream is a characteristic of the disease.
Medications used in the management of Kidney Mineral Bone Disease
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- Calcium-based phosphate binders: Calcichew, B Cal, Eno TUMS, Phosphosorb.
- Non-calcium-based binders: Sevelemer (Renagel), Lanthanum (Fosrenal).
- Active Vitamin D supplement: Alfacalcidol (One Alpha).
- Cinacalcet (Sensipar) – Calcimimetics increases the sensitivity of calcium receptors resulting in a reduction in PTH levels and calcium and phosphate resorption from the bone.
Suggested Interventions
Medical Aid Motivation:
Here are some of the medical aid requirements to motivate for the following medications:
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- Phosphosorb: Motivation letter plus an eGFR no older than 3 months.
- Sensipar: Motivation letter plus the following blood results; Calcium, Phosphate, PTH and an X-ray showing complications of renal bone disease.
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REFERENCES:
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- K/DOQI Clinical Practice Guidelines for Bone Metabolism and Disease in Chronic Kidney Disease: American Journal of Kidney Diseases, Vol 42, No 4, Suppl 3 (October), 2003: pp S12- S28.
- South African Renal Exchanges 2005